Common BMW E46 Cooling System Failures

The E46 was an amazing platform with one of the best engines that BMW ever made as far as driving goes, however its cooling system wasn’t exactly rock solid. There are a lot of common failures that need to be addressed because the one thing you do not want to do is severely overheat an M52TU/M54 engine because the cylinder head will warp, the metal in the block will fatigue and the head bolt threads will pull right out and your cylinder head gasket will fail. Basically, you'll have a really bad day, so make sure you address all the problems I list in this video.
Intake Manifold Removal: • BMW 330i 325i E46 CCV ...
Thermostat Housing & Water Pump: • BMW E46 Thermostat Hou...
Radiator & Expansion Tank: • BMW E46 Radiator and C...
This video is for entertainment purposes only. 50sKid assumes no liability for any repairs or modifications performed by the viewer as a result of the information contained in this video.

[@nenorv11]

Jason, you are a trooper and still helping the E46 fanatics. Thank you kindly.

[@KD-rf1pz]

Recycle bmw key

[@alexromero7532]

Absolutely agree

[@kingakim11]

hella trooper

[@NikitaAnnenkov]

First ! Glad you’re still making E46 videos! Thank you so much!

[@chadriddle3517]

This man speaks the truth I have a 46s and have replaced every single thing he listed facts

[@camryuser]

Hard-core BMW guys get mad if you tell them about the cooling system, I dunno why. The water pump impeller is plastic. They deny these facts.

[@chadriddle3517]

@@camryuser yes it certainly is from the factory or oem replacement. I replaced one on mine and it had a metal one in there that had a bearing going bad and it scarred up the block.

[@chadriddle3517]

@@camryuser yes it certainly is from the factory or oem replacement. I replaced one on mine and it had a metal one in there that had a bearing going bad and it scarred up the block.

[@NakaiSan.]

I have m54b25 and it is awesome car. Atemporal and so nice.

[@NakaiSan.]

@@camryuser u pref a camry or a m54 xd

[@reggiekush425]

Your E46 Content is GOLD!! You've already helped me replace my ccv system, power steering reservoir and lines, and some miscellaneous suspension stuff. Thank you. I really appreciate it.

[@SirChad771]

Thanks for keeping the peace of mind & accurate info in the E46 community!

[@TomasLineros]

You rock, man. Thanks as always for sharing all your experience and knowledge with these cars. With all your DIY videos you get that anyone who's thinking to buy one of these cars decides to go for it and fix it by themselves. Greetings 50sKid. 👊🏻

[@wellokayyes1266]

This is a really great breakdown of all the parts in the coolant system. I appreciate the order they were all put in as prioritizing was completely accurate.

[@peterastley-sparke7526]

Great to see you back and making more videos on the E46 :-)

[@cmccann4]

agreed!

[@petepenn1]

Crucial Info Your timing is excellent. Have 3 E46's and you have been a Great teacher! THANKS for All your super shots and Editing!

[@dannymatthews855]

Thank you for all of the e46 videos. You always cover repairs in a way that I can easily follow. They are so valuable when working on my 330I..

[@Stomper]

Good video Jason and reminder for my next interval. This video was due for some. I've done this maintenance every 35k for peace of mind. I beat on my E46's cooling system from Cali to AZ to TX and to Vegas every month, sits at 151k. This is a must know and super easy to do for every owner with the M52TU/M54 engines. Please folks use OEM parts as he says trust me don't cheap out.

[@VincentMMoore0]

Your videos are smashing good with info! I changed and replaced every component in the cooling system in 2020 (2003 325i). Those hoses on the engine block are typically corroded as you say. I would add for those who have the problem of a broken hose-end stuck in the engine block, there’s a great video of a z3 owner (same M54 engine) who has a hack for removing the stuck pieces. Basically - get a 3/4” tap and a 3/4” bolt. Tap the hose crud and then thread the bolt in and use elbow grease to pull the stick pieces out.

[@auck1969]

Since I've bought my 05 330CI ZHP your channel had been a GOD send. A million thank yous!

[@VicOrlando]

I've gone through these vids, I just fixed a stuck thermostat. I just wanna say whatever you been doing, you're lookin thin bro! Much healthier man before us. Nice work!

[@pianothatilove]

Great video and a very good reminder for what is required if you want to drive around in somewhat reliable vehicle

[@johncoss5604]

Great advice. I need to replace all those items on my e46. Thanks for the reminder.

[@clubsport_46330]

The e46 Community would never have enough of your videos...we need more hopefully more would be coming

[@lp2565]

Exactly.

[@SamAbraham]

Thanks man! Applying most of this to my E39 530i. Also replacing the torque converter next week thanks to ur vids. Did the transgo regulator already!

[@mohammadalnuwaysser1974]

I like watching your videos, they are very useful Thank you for putting the effort to post these videos I wish you can cover everything about SMG & SSG transmission too

[@dmitrygear]

Working on my second E46 project and agree with all points you made!

[@ricardortega00]

It is funny that i found this video only 2 hours after it was published and it already got over 1k views plus mine, great content Jason, you have been saving our e46s since at least 2016.

[@lp2565]

The guy is the E46 guru!

[@getitdonegarage]

The calm man alive

[@baggszilla]

Thank you for this and all you do Jason!

[@hardyschilling644]

One more thing to check out: the cap of the expansion tank. This thing can start to leak or (worse) it will stop releasing steam at the supposed pressure (2bar for the m54 engine). Cheap and easy replacement that should not be overlooked.

[@lp2565]

Definitely! GAS makes a great modified one.

[@AlecKristi]

Will also most likely save you from having to replace the expansion tank...

[@Residew]

@@lp2565 THANK YOU!

[@mry82]

@@lp2565 Exactly. I got one... 1.2 BAR if I remember correctly. Others also use (I think a 1.5 BAR) cap from e30, etc...

[@emineid]

I do not think lower pressure caps do anything for the most part. Here is the thing: My experiments with the 2002 325i shows that the coolant pressure does not really ever go above about 1.25 bars. The pressure fluctuates in the 10 to 18 psi (0.69 to 1.25 bars) range during driving. The pressure is NOT regulated by the cap under normal driving conditions. The pressure fluctuates due to the micro-boiling in the cylinder head coolant passages next to the exhaust valves. This is the reason why I conclude that lower pressure caps in general are not helpful for the most part.

[@matts826]

My e46 overheated last weekend and it looks like the thermostat packed up in the closed position resulting in so much pressure it took out the expansion tank, the radiator, and the hose between the exp tank and the thermostat, luckily the head gasket seems ok thankfully! All advice in this video is defo worth listening too.

[@Arthedes]

I would do a leak down test to be sure

[@2091Ted]

The EXACT same thing happened to me just a couple days ago! The expansion tank explosion was so ferocious it was almost unbelievable!

[@lilkloud]

Just do the whole cooling system like I did

[@aor3200]

Unfortunately i cannot agree with you about oem water pump breaking for plastic pieces. I have been working with M54 since 2005 and never saw one failure like that. I don't remember any cases in our local BMW communities, and yes M54 + M52TU´s are very common everyday drivers still here. In fact, all OEM original stamped pumps from 2003 for example have been in very good condition, no leaks or anything. Replaced just because of age. I always use Saleri pumps, never had zero failures with Saleri. PA659S model for M54. People dont know that lof of cheap metal impeller pumps are china production and very poor quality. Personally, i use only saleri with composite impeller. Btw. You are doing great work with videos. Thank you!

[@timboyle3114]

I've had 2 metal impeller pumps fail very quickly on my 99. One with a cast impeller - completely cracked off the end of the shaft and destroyed the bearing Was very lucky it didn't cause serious damage. Another stamped impeller where the seals failed very fast . This is on a manual so no fan on the pump to to cause extra stress. Usually use Graff pumps but currently running a BMW composite impeller on my 99 right now after my last Graff failed. Though I am running Graff's on my other 2 3's with no issues.

[@utahyork3338]

Just replaced the plastic tubes under the intake manifold on my 2001 (200K+ miles). I put this off because I was afraid to remove the intake, but watching your other video gave me confidence. And yes, the end going into head broke off. I had to use an expansion tool to pull out the piece. With the intake off I also replaced the four rubber heater hoses. You are GOLD my friend - GOLD.

[@petepenn1]

Jason is Platinum Now!

[@hr007njnnnkkmkm]

Love your E46 platform content

[@rogersmith1203]

Thinking of doing my cooling system soon, great content!!

[@lp2565]

To any new E46 owners. This guy is the guru. Note all of this shit. He knows what it is about. Love the 50sKid. The Master!

[@antoniogonzalez-gr5qg]

just purchased my first e46 and this video was super helpful thanks

[@MyDriverX]

im so glad youre back!

[@Ch3kThat]

Owning an e46 will be so easy knowing I have your videos to fall back on

[@zWallyHD]

You should've mentioned the 2nd coolant temperature sensor. The one under the manifold. Because of its location it's a PITA to replace and should ALWAYS be replaced if you are changing the two hoses connected to the head of the engine.

[@hobbyguy2700]

Dude you look amazing! Hope life is treating you well!

[@troylogan3653]

Absolutely your videos are the reason I just picked up a e46 330xi a few weeks ago. Had one before but got totalled a couple years ago. I just love the way they drive and handle. Bmw has lost the essence of the ultimate driving in my opinion. Everything now is just all about speed and sticking an M emblem on everything. It used to be an exclusive club now its just ordinary. Bring back the old ways of bmw for us older enthusiasts.

[@jonowen6612]

Jason speaks the truth. At the beginning of pandemic, I did replace all of this except the two hard lines under the intake manifold on our 2002 Z3 Coupe with the M54. Now I’m thinking I should go back in and remove the manifold to get these two hard lines. Cooling system should be redone every 100k miles or 10 years.

[@NNJJDD5427]

Man you are one of the e46 youtube kings! Keep whit the videos, you are the reason for many of those cars to be on the road, you are a legend!

[@petepenn1]

So True Jason has saved many E46's and us owners thousands!

[@2Jupiter]

Yes, The One Maine Weakness on BMW E46 is the cooling system! I´ve already Replaced The: 1- Coolant Expansion Tank 2- Replaced the OEM Water Pump With Stewart Water Pump 3- all hoses & Thermostat Housing 4- And new Radiator All At the Same Time :-) ! All are OEM Genuine Parts. Great Video! Glad you’re still making E46 videos! Thank you so much! And Thanks for all your Tricks and Tips on BMW E46 :-)

[@ggua92722]

Thank you Jason! My hard line under the intake started to leak due to corrosion. Replaced it around 190K. Now my E39 has 212K. Very easy to replace once the intake is removed.

[@outdoorframes]

Hello, may I ask if the leak was bad enough to leave you stranded on the road? I was wondering if these hard lines develop sudden crack like the expansion tank or do they develop mild leak at first?

[@GreyBBeard]

I would add the HVAC heater control valve located right next to the firewall. I had the hose nipple on that crack off completely on my 2002 Z3 and instantly empty out my entire coolant system. Fortunately, I just pulled in to park. Had it happen a day earlier, I would have been on the freeway, and the engine would have been fried. I like the radiator by Zionsville. It is welding artwork.

[@newtonraymond77]

My first time ever touching a BMW recently my coworker gave me a X3 which I gave to my sister, but before I gave it I did everything you mentioned including idler pulley, belt tensioner, front driveshaft, all four brakes and rotors, oil change, cabin air filter replacement and cleanup of all cavities that harbor dust and leaves. It took a couple of days because I'm not a mechanic but I read and attend KZbin University.

[@petepenn1]

Bravo Bro you're a Great Giver! Respect!

[@Jonathan-tb6fm]

Love your videos ! I think we owe him some headlight covers.

[@davidjoseramirezbravo4525]

Glad to see your 330i again and thank you for this video 💘

[@bogusienombre355]

Nice new logo. Looks fresh!

[@mikeault7]

Very helpful I hope I can find ur videos as I move forward w my repairs 04 325i (coolant pouring out as fast as I put it in )

[@CaffienatedMothman]

Hey my dude, I love your videos. I just blew the expansion tank on my e46 and you've been guiding me through replacing practically all the engine gaskets, along with the CCV while I'm at it. I was wondering if you had any suggestions for cleaning out the oil buildup in the M54 intake? It looks like you've lost a bit of weight and I'm hoping thats intentional. I really appreciate your videos and would love more on the e46, but not at the expense of your health. Take care of yourself.

[@50sKid]

Very intentional, I've been working out every day since February. My advice on the intake is to not worry about it, because even if you clean it out, it'll go right back to being that way within a week. If you hate the idea of this in the first place, you can switch to the catch can. If you want to clean it out after that, remove the intake and go at it with soap and water and a garden hose and let it dry out, but even if it's a bit wet, that won't hurt the engine -- actually it'll help it because water/steam decarbonizes engines.

[@petepenn1]

@@50sKid Great advice as usual! Got a blocked cat on the right side, no exhaust out the passenger side. Got any ideas to fix it or just pull it? Thanks again and you look Very Healthy...Cali sun is sweet!

[@50sKid]

@@petepenn1 Is your exhaust flap just closed? If your cat is blocked, you need to replace it.

[@projman2155]

Did all of these on my X5 3.0 M54 manual. Wuhoo! The only pain was the coolant splatter was so strong because the auxiliary pump is close to the expansion tank. I couldn’t use the bleeder screw so I used the stream inside the tank to observe bubbles but I had to use towels and a face shield while bleeding.

[@longislandsound1996]

Life saver ABSOLUTELY LOVE MY CAR…dope channel

[@paulheyes653]

Wow youre back doing vids but youtube hasnt notified me !!! The walking talking e46 manual himself !! KZbin notifications changed !!

[@davidramez6219]

Yay! More E46 content!

[@oiygfdxssfgg]

You're a good man Jason

[@livemadseason]

Wow, you got so skinny I almost did not recognize you. Awesome change! :)

[@richardgalvez3740]

Keep it up J!

[@Horrokotoj]

Hi! Thank you for great videos! My e46 is running cold. I changed the thermostat without any significant improvement. INPA shows plausible values from the two coolant temperature sensors so I do not think that is the issue. Do you have any suggestions or have heard of a case where an m54 engine is running cold where the thermostat was not the culprit?

[@busterscrugs]

Previous owner of my car had installed an aftermarket coolant temp sensor on the lower radiator hose, and it was leaking through the connector. O-Ring was fine surprisingly lol

[@garrettgiuffre8505]

my E46 was serviced for the waterpump hoses etc about 60k miles. my waterpump detonated I now have the metal water pump

[@mannabatth4092]

Great to see e46 video 😍

[@tkajtsai1586]

Well said

[@MichaelAMangone]

I have replaced every single component you mentioned, and I did it with your videos. I learned some things, too: be careful with the replacement radiator: it has to be one labeled for a manual trans if you have a manual-- (duh!) But it's easy to mistake because about three years ago, most companies stopped making transmission-specific radiators for E46, and they just threw in a conversion kit for auto to manual transmissions. The kit works, but the fitment is bad. An old-stock Mahle designed for a manual trans car fit like a glove. For all other parts, I bought Rein/Continental. German made, but very cheap. No problems with fitment or leaks. Oh! Except the water pump. I bought a plastic impeller unit from an Italian company because of this logic: if a metal fan breaks up, that will be the end of the engine; if a plastic fan breaks up, that's 20 dollars for a 5 liter jug of coolant for a thorough flush.

[@LunaticFringeHunter]

Damn, that was a great video... thanks so much.

[@ron8566]

Jason - have you done a video on clearing the rear sunroof drains on an E83 X3 with the pano roof? I cannot seem to clear one of the rear drains and I am about to cut the drain line inside the rear hatch side panel to be able to get a trimmer sting in there to try to clear out the rear drain.

[@Soul_Reaper]

Got 175k miles on my 325i have yet to replace any of those but getting a feeling that I should before It’s too late. As always love watching your Got 175k miles on my 325i have yet to replace any of those but getting a feeling that I should before the car decides it’s that time now lol. As always love watching your videos!

[@pyscobrand]

"When" not "if". So true. When I went to pick up my 325i from the city, I made it two blocks before the upper radiator hose exploded. Thankfully an auto zone a few blocks away had the part in stock and a friendly old guy loaned me some tools to get me going. People, replace your cooling system. When I got the intake manifold off, all the cooling lines were cracked. Miracle of God they didn't break on the 38 mile drive home.

[@outdoorframes]

Hello Jason, do you know if the leakage caused by the hard coolant pipes is usually bad enough to leave you stranded on the road? I was wondering if these hard lines make sudden crack like the expansion tank or do they develop mild leak at first?

[@nsdlsarn]

Thank you for your videos

[@randallmartinez2476]

Jason, my name it Randall, Denver CO, a web designer like you. I’m a bit fan. You are my go to guy for any thing E46 related. So I have a 2005 330xi with a chronic over heating problem,. I’ve replaced everything once twice even three times to fix this, and still my car overheats. So the last time I drove across town and my car overheated, I cranked up the heater and the temperature almost immediately came back to center the way its supposed to be. Obviously I can run my heater at full temperature during the summer. An suggestions on what else I should check and replace?

[@masinicudetoate3913]

Hello from Romania! Y am a huge BMW fan from my childhood when my father have e30. This year y completly restored an e46 compact and swap to 2.8 TU, last year am e36 coupe 2.8 stock..and next is e46 cabrio 3.0

[@phredmfalme2498]

Just replaced coolant tank water pump and thermostat. Houston is hell on coolants systems.

[@alph4official187]

This guy is really a genius

[@Andrewlone174]

My only car i love in this world and newer buy another new, thanks for all wideos about e46 it's will be a good manual for many years.

[@DankUraniumYT]

My list so far Radiator: Mishimoto aluminum Thermostat: Aluminum Radiator hose: Silicone Lower radiator hose: Silicone

[@ipiep3959]

Learn a lot from you on my E46 👍 👍

[@FstSgtHromushin]

Thank you God of e46

[@lefora87]

you're the best thing to ever happen to the BMW community.

[@e.a.7265]

Spot on Jason!

[@drago22alina22]

Perfect timing, i took out the manifold to change ccv and vacum hoses, plugs, and doing stage 3 cooling, changing all those hoses underneath the manifold plastic and rubber ones, also might clean the injectors, debating whether i should replace the starter while im there, but not sure yet

[@DjDestinyChicago]

If the starter is old, I’d change it. I did 👍

[@emineid]

I did. It was one of those "while you are in there" decisions. You did 90 percent of the work of getting to the starter, so why not?

[@JB-ex8kl]

Yup, do the starter… sooo much easier w intake manifold outa there, but still a “bear” to do, but you’re saving a lot of $ doing it yourself! AND - the best part is knowing you’ve done it right … not a tech at the stealership in a hurry to go for lunch!

[@petepenn1]

@@JB-ex8kl Right on, peace of mind when you go it yourself!

[@Audioworks_producciones]

Hi Jason, I changed my heater hoses under the intake, but one cracked inside the base, I was able to pull the most of the cracked part but im not sure if all came out, can be a problem if a litle piece of this plastic is still in there?

[@chuysxo]

Thanks man

[@feisty_capture3944]

Hi, I'm having a overheating issue on idle or when going really slow, I'm thinking it's the fan clutch any ideas? If I go to high revs in neutral temp goes down,

[@jimiheil8007]

Hi Jason! Hey quick question I did a cooling system refresh hard lines under the manifold expansion chamber thermostat electric fan conversion hoses lower sensor blah blah blah bled the system properly but the engine still runs at 101°C dropping occasionally to 98 Celsius it typically ran at 96 I can’t figure this thing out any thoughts thanks hit me back when possible! Also the thermostat was OEM but from O’Reillys I’m thinking maybe it’s not exactly proper I don’t know?

[@Paul-gj7qu]

Hi. Could do with your help. Installed a new expansion tank on my bmw 330 automatic, now it won’t seal. It’s sits flush to the mountain bracket that attached to the radiator. But when filling the expansion tank with fresh coolant it’s just leaks outs. What would you suggest!

[@bdavali4342]

Great video, Jason! I did have a question: I had an E36 before this and there was a plastic (of course) airbox heater fed by a coolant line to pre-heat the air. Never knew it was there and it wasn't changed out with other coolant system maintenance so naturally it cracked and left me stranded. Does the E46 have such a device too?

[@timboyle3114]

To the intake air box - No. It also does not have the plastic 3-way pipe fitting on the firewall to the heater that can crack and fail as well. Plenty of other places to worry about though!

[@djuanejackson4215]

I did everything he mentioned when buying a 2004 E46. The one big mistake I made was allowing the Shop to go with a Behr Hella Expansion Tank. (now made in China) It cracked after 1 yr. and my car overheated! Please do as Jason says replace these with a BMW OEM Expansion Tank period. I go mine from FCP Euro with a Lifetime Warranty.

[@runepetersen10]

What about Febi Bilstein? Is that ok?

[@Videos-os3cc]

What happened to your engine after overheating? Is it still working?

[@sosagls]

@@Videos-os3ccoverheating doesn’t necessarily mean he continued to drive it

[@myrajuju02]

Same failures here with 2005 m3! Glad that’s over for now:)

[@herrbrahms]

I know the truth about the hard coolant lines but am sad you mentioned them. Pulling the intake manifold gives me the willies -- probably irrationally. I've done everything else on this list along with the accessible heater hoses running along the left frame rail. *sigh* I know eventually I'll have to do the CCV system too. I did at least do the 02 Pilot mod to suck as much oil as possible away from the rings.

[@joeorlando94]

I noticed the bottom part of my radiator cap/expansion tank cap broke off. Bought a new Mahle one. I now noticed the upper radiator hose will collapse a bit now after the engine cools. Is this a defective cap or just a need to change the hose? It does feel a bit soft. But if I put the broken cap back on, this hose does not collapse.

[@antiochiaadtaurum3786]

i've a feeling that a leaking oil filter housing gasket and /or vanos oil line in the same area could be leaking oil all over those hoses that are underneath the intake manifold - if so, that would surely not be good for those hoses in particular. Also, those hoses are totally out of sight, and as someone else said, get overlooked on that basis.

[@bublescool]

Yeah, learned the hard way, about this damn oring around lower hose temp. Sensor. Slammed it into the new hose without care in the world, this little bugger was leaking like crazy.

[@dustincercado]

What were those engineers thinking of when putting a plastic hard line under the intake?

[@zeroyon4562]

I had an E36 with the M42 engine and they have a plastic coolant line in that same location too, the one on mine split and the engine lost all the coolant, cracking the head.

[@paulnastoff2394]

Repair dollars!

[@elbereleee]

Hello, I have a e46 330xi and wanted to swap it into rwd, but not sure the engine supports of the two are similar in the front. Do you think the two front spots of the xi subframe bolts into the same place as rwd? Do you think it would swapable? Thanks.

[@warlordcheeky2166]

Hay mate I have a question..iv changed my expantion tank thermostat housing water pump an radiator an expantion tank thermostat an the coolant temp sensor an the water level sensor..but my car still overheats..any ideas would appreciate it..an also my fan runs when the car is cold an stays on 10 seconds after I turn car off..my upper radiator hose blows out steam slightly to wen it gets hot..tia

[@kawarider9049]

Thermostat heating element is NOT for heating coolant when car is cold. It’s there to heat wax in thermostat - so ECU can electronically change thermostat opening temp depending on engine load (you can find thermostat temp map in ECU - for example in higher RPMs and/or more air flow into engine, the ECU switches the heating element, which heats the wax and that leads to keep thermostat open even in lower coolant temps, for this high rpm/high air flow into engine its only 84 degrees celsius I think). You can try it - open nr. 7 in cluster hidden menu, heat up the car to 97 deg celsius operating temp and push it hard on highway - the car immediately opens thermostat and drops the temp to like 84-86 deg celsius. Dont take it as critics, its just to inform others about how the old BMWs heated thermostat works:) Great video, as always, thank you!

[@BimmerCult]

got a 2006 x3 m54b30 engine that keeps getting air in the system I've already took it to galleria bmw twice and they said the engine pressure is good but can't seem to find out what the problem is but after driving for 1 hour hour 30 minutes my coolant light goes off and I check the expansion tank and it has a lot of air in the system. Just replaced the whole cooling system 2 months ago

[@Equinoxious342]

Absolutely the truth - best thing if buying an e46 - take the hit and do the lot; they are getting old now. Means pulling the inlet manifold but it's not if, it's when as Jason says. Be really careful with the hoses under the manifold as they can snap where the hose enters the block making it difficult to get out. Best way is to stuff a rag into the block from the thermostat opening to prevent bits going into the tunnels. Use OEM coolant - not cheap stuff.

[@jahiemj9688]

Looking good 👍

[@mailpup]

It might have been implied but I would specifically mention replacing the rubber heater hoses when replacing the hard coolant lines. Might as well since it's easy when the intake manifold is off.

[@lp2565]

Definitely

[@timboyle3114]

99 328 - 200k + miles. I think I've had everything in that list fail at least once header tanks / water pumps multiple times. To be honest after 2 catastrophic cooling system fails - all these items I now consider service items - will replace every 7 to 8 years max no matter mileage. Luckily engine survived both times as I stopped and got a tow. Would also be #1 on my list to replace if I buy a new 3. Start with header tank / pump / thermostat at a min, and include the others if they are looking at all suspect. The tricky ones are those hard pipes, Just no way to give them a good inspection as they are hidden under the intake.

[@dillonhall7417]

Where do I buy the rigid plastic hoses under the intake manifold? Though I had everything right after I changed my head gasket, but neglected those hoses

[@michaelblacktree]

Hey Jason, have you tried a lower pressure expansion tank cap? Supposedly, the lower pressure puts less stress on those plastic components, so they last longer.

[@emineid]

A lower pressure cap does not help for the most part. The pressure is "regulated" by how much local micro-boiling that happens in the cooling passages next to the exhaust valves. The typical actual pressure runs 10psi to 14psi in this car, almost always less than 1 bar. The pressure cap only comes into effect in a catastrophic event when the whole system is about to blow. Exception: if you overfill the expansion tank, the pressure will run at 18 to 20 psi, so don't overfill obviously. I repeat: In all cars, the actual running pressure is not regulated by the cap. The pressure is "regulated" by how much local boiling occurs in the cylinder head, so in effect, the pressure is not regulated but does stay several psi below the rated cap pressure for the most part. Interestingly, a 2010 Honda Accord will run 4 to 14 psi all day, sometimes zero psi!!! A Genesis G70 will run 14 to 18 psi all day. Every car is different.

[@michaelblacktree]

Lots of engines run in the same temperature range, with a much lower pressure rating on the cap.

[@50sKid]

Haven't tried it myself

[@emineid]

A lower pressure cap will do absolutely nothing on an E46 for the most part. I have run both the stock and the lower pressure cap on my 2002 325i. I have a pressure sensor hooked up to the upper radiator hose. The pressure readings are identical whether you have the stock or the lower pressure cap. That is because the pressure almost always runs several psi BELOW the pressure rating of the LOW pressure cap. The coolant pressure runs in 10-14 psi range for the most part. The pressure is NOT regulated by the cap (except when something goes wrong and all heck is about to blow up). The best preventive measures are: Replace the parts (expansion tank, etc) before they fail, and bleed the system properly (use vacuum filling system if available).