BMW E46 Radiator and Coolant Expansion Tank Replacement DIY

Behr radiator: amzn.to/2KsmHrG
Genuine expansion tank: amzn.to/2M8ZW1e
I tried my best to purchase OEM components, or at least OEM brand. I rarely buy parts from the actual dealer because they are just grossly over priced. In most cases the manufacturer will make the exact same part for the parts market at a cheaper price. I usually buy things through eBay.
I bought a Behr radiator that seems to be made in South Africa and a Coolant Expansion Tank from Behr Hella (they outsource this to China now). Hey I guess American companies aren't the only ones outsourcing, lol.
Turns out my expansion tank and radiator were already replaced at some point in the past by the previous owner, although he didn't tell me that. No big deal, I'm glad to have good brands in my cooling system.
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.

[@MrDanoman812]

Thank you for ALL the videos you've done on the 330i. I just got mine a couple weeks ago, took it to the mechanic and almost fell out of a heart attack when he told me all the things i needed to have replaced. (it's got 164k miles and apparently the previous owner didn't believe in maintenance... lol) So, it's getting some of the deep major work done on it right now and once getting it back, looks like i'm doing the rest. Being that i worked as a mechanic on cars in the ARMY, i have some idea of what's going on under there but, after seeing your videos i'm not as spooked to get my hands into a BMW now. You Sir, have just saved me tons of money by switching to working on the beast myself. :) Sincerest thanks, bud...!!!

[@50sKid]

Thanks! Good luck!

[@austin4920ify]

Couldn't say it better myself. This man saved me from so many headaches

[@GK-Greece]

@@50sKid One question,at morning when car is cold I open the cap and I here sound like air coming out,like open a Coca Cola(pssshh),no bubbles or something! Is this normal or I need to change cap???

[@50sKid]

@@GK-Greece Normal

[@mikedj420]

***Full bleed procedure*** Bleeding the cooling system is necessary, and if skipped or done wrong, can cause very expensive damage to the engine. Thermostat needs to be open (engine warm), and climate control heat on full speed at highest temp setting with ENGINE OFF (per BMW spec. This differs from a typical bleeding procedure.) Make sure the car is level or the front slightly elevated. Fill expansion tank to very top (past fill), loosen bleed screw, wait for bubbles to stop, while adding coolant to keep level at top of expansion tank. After no bubbles come from bleed screw, close it, then remove excess coolant from expansion tank with turkey baster or such (this step is important), leave it a little past cold max fill because the coolant is warm. Check coolant level (when cold) the next few days, top off if necessary. One last tip, don't open the cap if the car is warm because hot coolant will spray everywhere. Warm car up with cap off if you need to warm it up.

[@DD-it1th]

What’s so good about your videos is that you tackle it and explain it exactly like a home mechanic….like most of us. This makes it so easy to follow. Whatever car you go for next I will certainly look at. For now I have a Z4 E85 M54 3.0 which I believe is pretty much the same as your E46. So thank you 👍🏿

[@vicnaumov]

the most informative vid on the cooling system overhaul. the best one i've seen so far. especially the part of the engine drain plug.

[@romeomike8918]

Thanks for the videos. Besides being clear and thorough, they’re great confidence builders. Some observations for others as I had to drop the radiator as part of replacing a leaking power steering cooling coil: The replacement Behr radiator coolant drain plug takes a 22mm socket. With the ATF heat exchanger and its two black o-rings, it’s a great idea to install new o-rings. My old ones wouldn’t stay in the grooves, and the last thing I would want is to have an immediate coolant leak after putting in the work. Great suggestion dropping the radiator out the bottom. My lower radiator hose would not come loose at the radiator connection, so I managed by disconnecting it at the thermostat housing and was able to drop and raise it back from below.

[@tonyasm4846]

Thanks great video. I bought a 2003 325i BMW with 53,000 original miles. I changed the whole cooling system after watching your videos, was very informative. I plan on changing transmission filter and fluid this weekend. Thanks for the videos really appreciate all the knowledge I have gained from watching your vids. I think they are the best one's on KZbin.

[@jeffbirrell9529]

Great video. Just did this job, plus belts, tensioners, water pump and thermo and hoses. Disassembly was easy but it fought me all the way going back together. I do think that the hose connectors​ are better left with the clips down. If so, you get a nice positive "click" when put back on. Thanks again.

[@austin4920ify]

Wow. Here I am, yet again. You are guiding me through another BMW headache. THANK YOU! 🙏

[@therealzooch]

Thanks, helped a lot. My thermostat was cracked the same way and I had a lot of trouble trying to figure out whether I actually had the part or not. The little plastic part on the lower O-ring was probably the ridge which held the o-ring in place.

[@paintboy7625]

Another great, informative video from 50's kid. I will be doing the same thing on my 01 325i and now feel confident I can get it done correctly. Thanks.

[@jasonb8407]

Just bought an 05 330ci ZHP for my son with 122k miles two weeks ago. Just found a small coolant leak from the radiator so my son and I will be doing a cooling system overhaul in about a week. You sir are a scholar and a gentleman.

[@Lineysraceroom]

Mate your a legend. Changed my rad this weekend on my e46 325 ci curtosey of your video. Great videos keep the vids coming. 👌🤙

[@harmzsingh8045]

Another great vid! A job I've had the displeasure of doing twice (buy cheap, buy twice and all). Keep up the great work.

[@startv7472]

Awesome. No one would tell you about E46 that much for sure. Thanks for your efforts

[@agustinreyes6111]

Watching your videos has saved me thousands of dollars!! Thank you.

[@blond339]

thanks for the help by making this master class how to vid, i just did a radiator replacement on my 05' 325i m56 - i found a sulev oem behr radiator for 145.00 and the expansion tank thermostat (also oem for 45.00) that is working perfect so far. only needed to replace the upper hose as the coupler to the water pump was crumbly. i found when putting the fan back on impossible until i put a large sponge (works well against the radiator because its soft enough not muck up the fins) between the fan and the radiator holding it in place making it easy to spin it back on. there was no way i was going to be able to hold it in place and get the spanner in there, just not enough room. so hopefully that's a useful tip. cheers

[@jesus127681]

thank you so much i know its been years since this video has came out but i recently got my e46 and a lot of your videos have greatly helped me. thank you

[@gregagnew1628]

Great video! I really appreciate all of your videos. You have become my go-to video guy for my son's E46 Touring.

[@ynebogatov]

I'm in the process of putting about 1k worth of new parts (accumulated over a year of procrastination) into my 2003 e46, everything from cooling system overhaul to replacing the starter. Your vids are simply amazing and probably saved me *days* worth of wrenching. Great content!

[@50sKid]

Thanks!

[@superguitarstar1300]

50sKid how many gallons of coolant do I need to perform the job?

[@aor3200]

I did this job some years ago, nice and easy for manual at least. These videos are really helpful. Thanks

[@Volvo8Fifty4Life]

One of the best how-to videos on youtube. Keep it up man!!

[@chris24hdez]

15:17 removal of the automatic transmission oil cooler thermostat. This segment saved me a lot of headache! Thanks!

[@sbrochew4699]

"More fluid, huh? Crazy!" That about sums it up! Great videos man. I am a Parts and Service Manager for a BMW/MINI independent and just bought my son a 03' 325i. Needs A LOT of work. These videos have been awesome. I sell this work all the time for over 16 years but never actually did the work myself. Your videos and channel have really helped me and my son bring his E46 along. Thanks a bunch man! Keep them coming. Side note, I could not find a single video to replace the rear locating arms. You know, the big set of tongs on the rear of the car that adjust camber. I know people sometimes call them trailing arms, which they are not. They get bent easily and tow trucks hook them. Can wreck some rear tires. Love to see that video WITHOUT removing the diff! Not easy with diff in.

[@frankryan8100]

You don’t have to remove the rear diff. Just loosen it up and slide it back a little to make room for the bolt to come back. By now you may have done the work but if not, go for it!

[@stewfly9227]

@@frankryan8100 we will never know if he completed the job or not.

[@jamesbarratt593]

I only had the thermostat and water pump to change, so I put a big plastic bin bag over the crank pulleys and it worked real well. Then removing the water pump, I'd let the water flow off the bag and underneath the car. Right so after changing that water pump and thermostat, and with no leaks, I'd run it. Didn't get more than a couple of miles before I'd seen the temp at three quarters. Switched off and went for a dog walk. Then coasted down the 3 mile hill with engine off and checked the expansion tank. It was full. I'd never got to the end of your video first time around and now wish I had. From the choice of e46 video's on ytube I like how you explain stuff. Anyway I googled e46 overheating after thermostat changed and wow. In a forum by a BMW tech guy, he'd spoken of a bleed screw on the thermostat and the expansion tank. He'd mentioned switching on the heater, and the air con switch. Then someone else mentioned about a bleed screw behind cylinder 2. If your way works great and I will try it. Do you know of a bleed screw on the thermostat its self? And the cylinder block bleed screw? Awesome videos mate. I have 170 on vw golf here on KZbin and really see how cars are so different these days. No one can possibly know all stuff on all cars.

[@nelsonalmeida7286]

Perfect timing! I plan on overhauling my cooling system soon! Thank you for the great E46 vids and please keep them coming!

[@scottsutcliffe5001]

One thing I learned on my 325i is that any time I have the coolant system open I reverse flush the heater core. If I don't the heater will not work until I do. Can't begin to tell you why but that's just the way it is and no amount of bleeding will fix it.

[@TheLubricon]

Thank you so much for this. You have no idea how much time and money you've saved me with your videos. Thank you, Thank you, Thank you !

[@GratitudeAndProsperity]

Cheers man! Thanks for the help and tips, I would also add that I would replace the damn temp sensor because that is the only place I had a DAMN leak, because of that grommet of course on the sensor.

[@TheHa11jesse]

When working on cooling systems I prevent all the mess on the floor by using shop vacuum and sticking the hose over the drain hole and then inside the lower radiator hose for a bit once it is opened up. Also when working with o-rings get yourself some Parker- SuperLube. It is the best product ever for o-rings. It is the only o-ring lubricant approved for use on Caterpillar machinery is where I first used it.

[@mogtabaa5586]

I have e46 2002 and your videos help me a lot ,thanks mate.

[@tng6628]

Thank you 50skid. This video is very helpful.

[@AMMstudios]

Luckily there isn't a whole lot of... OH GOD. Lmao. Great video man thanks.

[@matthewhummel3583]

He edited those parts out

[@Ken-we9jc]

awesome work brother! keep them coming. Excellent and detailed.

[@kurzjames]

Thanks for the video! I'm doing my cooling system refresh right now and using your video as a guide. However, my expansion tank REFUSED to budge. In my case it was easier to remove it and the flat plastic piece that goes between it and the radiator at the same time. I then pried that plastic piece off of the expansion tank. Thanks!

[@stewfly9227]

same for me

[@ozscorpio7]

Great vid, thank you for posting! just finished mine

[@nathanhelmstetler2591]

Great video and show exactly what is needed. Big thumbs up from a tech at bmw :)

[@lesleaconnelly3912]

Top job, love your vids, keep them coming 👍👍👍👍

[@MetalJoe0609]

that plastic ring that was in a stack up with an o-ring on the expansion chamber mount thing looks a lot like a common packing stack up used in aircraft. they put hard teflon or nylon or whatever plastic rings on one or both sides of an o-ring to keep it in place and provide pressure the make it seal properly.

[@robjenkins3713]

Great camera work, thanks. I like your attention to detailed info for the viewer, right down to pointing out the new drain plug design. I've found that spraying some WD40 (penetrating oil spray) as you gently wriggle those crusty hose joints up and down helps free them off. As you say, adding a light smear of silicone grease to all O rings will save a lot of headache on future maintenance, ditto adding copper grease to replacement bolt threads. I'm going through overheating problems right now. Every half hour it will start to boil up and I haven't worked out the root problem. I'm about to power wash through the fins to help shift any build up in there.

[@anthonyspeters7203]

You want to chk water pump bmw in there wisdom,l think not! Put plastic impeller on pump when its yrs old impeller fracture on shaft then becomes loose don't pump ANYMORE, there are out there replacement pumps aftermkt better than oem ,that have metal impeller! That l fitted.

[@1970PMD]

I don't know if I missed you saying it or not but part of the bleeding should also be opening up the heater core. Set to full hot the heater and let it run while opening and closing the bleeder screw. I am about to purchase an 2003 M3 so I been watching your vids. Thumbs up!

[@joeorlando94]

I removed the drain plug on the engine block first, leaving the radiator cap on, everything else tight too. Coolant comes out everywhere but at a much slower pace. I then opened the bleed screw a bit to increase the flow a bit. Once that’s drained, then I drained the radiator and also the expansion tank. I used a bigger pan - one meant for mixing mortar from Home Depot - to catch the coolant.

[@gentoolive]

My 330ci is about to hit 110k miles. I've read replacing the cooling system is a good idea around 100k, think this will be my next project. Thanks for the vid's, seems that anytime i am going to start a new project you have always done it before me.. Saves me time, thanks!

[@50sKid]

Nice, thanks. Part 2 coming up this weekend.

[@gentoolive]

Welp, i managed to screw that up. While pulling out the old expansion tank, i broke something.. Where the large hole on the bottom of the tank fits. There is broken plastic, a nifty spring, some copper plunger type things.. I'm not sure what part to even order, the Expansion brackets i see on ebay don't appear to have that with them. Any idea what the copper plunger and spring assembly is? Wish i could send you a picture of it.

[@gentoolive]

Looks like it was the Expansion tank thermostat, its in pieces! Cheap to replace, hopefully it didnt hurt the bracket at all, its kinda crooked in there and dont wanna come out!

[@XionUnjust]

Great vid as always man. Keep it up! -Jake

[@50sKid]

Thanks, man!

[@danlmitchell1508]

Great Video, I have to say, I watched the first flow of antifreeze and thought that sucks. Watched the second drain and thought wow that sucks. By the 4th one and your reaction and comment i was laughing my ass off. It was a punch in the nuts and i wasn't the one on receiving end finally. Comical (in a good way). Thanks or the laughs and AWESOME video.

[@RCWatson]

Great video, really helped me replace both of mine. Good job

[@kcsnow9447]

I'm about to get underneath my E46 to find my leak(s), so I haven't actually tried this yet...but coolant obviously goes everywhere. Seems to me something as simple as a plastic "washing machine drain pan" ($20-$40) might cover a large area underneath the engine, and would also sport a drain outlet (use typical ABS/Schedule 40 plumbing fixtures and pipe) to get the fluid out and away before removing the pan--the sides typically aren't that deep, so pulling it out too quickly might cause it to slosh over the sides, which pretty much defeats the purpose. So catch the fluid in the pan, and get it out into a smaller container for reuse or disposal, etc. DIY is your friend. I might put mine on a caster equipped board to make it easy to get it in and out from underneath too.

[@stancetv2005]

Thumbs up for having everything greatly described.

[@martsmarts]

You're so lucky. Mine at 97k kms. Never been replaced. Was totally HARD to remove

[@TedSchoenling]

it is common for the ATF coolant thermostat to break when removing the expansion tank. Always have a spare when you remove the expansion tank.

[@LeverPhile]

I installed that Behr Hella Made in China expansion tank in February 2017, and by Dec 2021 and less than 88k miles later it split along the side and leaked coolant when I was on the highway. Replaced with a genuine BMW tank.

[@stephenpato5524]

My impatience won't let me not ask before I've watched the whole video lol, but; 1. Does a new lower hose temp sensor come with an o-ring? 2. Should you also not replace the auto trans cooler o-rings too? 3. How likely is it the expansion tank mounting plate will break during removal? Might as well get and fit a new one since one is doing this job? Thanks!! Great series of e46 videos by the way !!

[@BMWETDS]

Hey 50's Kid! Just leaving you a comment to support your efforts in putting up the info and videos about these kinds of small repairs on BMWs. I really relate to you sometimes with the fight against the rusted nuts and screws on these cars, as most diy owners do for sure. Nobody will take better care of your car than yourself if you know what you are doing. Great job on your videos, thanks!!

[@50sKid]

Thanks very much!

[@gustavorock4616]

Hi Jason, thank you so much for you videos, you've been invaluable for me with my DIY repairs. I'm having a weird issue with the coolant level sensor (I believe) I had installed a new one from URO Parts without issue, but one day my alternator failed and the coolant light came on, I thought the sensor got toasted so I got a new one but the light is still on even though there's coolant and everything else is fine. Not sure if there's a fuse for that...Any ideas?

[@edgu71eg]

uhggggg i tried this once on a 325i 2003 model did not get far. only cuz I was a new do it yourselfer and didn't have all the right tools ty for all your vids

[@alwedworth]

Thanks! OMG I'm removing the cyl head, Dam Intense! Also on the ground on my back Wow...

[@Bionixx016]

Man you got so lucky with how easy all that stuff was to pull out lol

[@e30BMW4ever]

Great video as usual! Have you ever considered an e60 m54 expansion tank conversion? Same engine, everything should fit. The e60 expansion tank may be a little more durable than an e46 one?

[@giangulli]

Such good videos! easy to watch too. thanks mate!

[@ggua92722]

Grate video like always! Quick question you did not mention anything about turning on full blast the heater inside the car. I think we still need to do that right?

[@MsMatth33]

Great video. I need to buy a new radiator for my E46 (2000 323i). I notice there are different sizes for the core. What size radiator do I need? Usually there is a part in the video where you explain the new part. I may have missed it. Let me know. thanks.

[@arcsound]

Question: I didn't see you replace the trans cooler thermostat, which I believe goes inside the coolant reservoir tank. Did I miss it? Great video, as usual. E46 owners around the world are indebted to you. I know I am.

[@cdyjkr]

make sure you run the heater too, sometimes you get a big pocket of air in the heater core.

[@IsmailRidi]

Awesome vid, Thanks! you mentioned that you were gonna hose down your engine. Can you tell us or maybe make a video about the safest and best way to clean the engine bay? what to cover? what to watch out for, etc...

[@IsmailRidi]

Can't wait! did a stupid mistake and my engine bay is almost covered with oil :( and want to know the best way to clean it. Thanks!

[@mn08th]

Thanks for the videos really helpful for novice like me! I'm trying to drain the coolant from the engine block on my E46 320d but I can't find the drain screw on the block. Is it in a different place on this engine?

[@tk2070]

50's goddddddd! Strikes again

[@dopvmine_p]

Always on point for vids... keep it up.....

[@98ron]

OEM is Behr Hella - I just took mine out it has a sticker the exact time and date it was fitted in BMW factory 09:07hrs 27 Jan 2003!

[@seandineen1134]

"More fluid, huh....." @ 12:22 is good stuff!!!

[@andrewglover9874]

Use some of the grease on the screws when you put them in, makes it easier to torque...also works for wood too.

[@mrg7721]

50s kid and Shop life all E46 owners need

[@straight6petrol67]

I do love your respect for the previous "wrenches" that have been in there, although we all know the saying... You want a job done well (watch 50s kid) then do it yourself!

[@Dat550go]

Did the o ring on the coolant manifold leak? (The one where you thought the previous person broke it off..)

[@kennyspringer7668]

Thank you for all the videos you have a question my radiator came with the same style drain valve however it is just a short Stub it doesn't have the as an automatic trans would do they sell a replacement to make sure it is flowing properly to the transmission cooler? I looked all over I can't find one without wing tabs

[@RepairDude]

Modine is the OE brand if you're curious. Literally has the BMW logo dremeled off

[@edvardkall3381]

Great video! The colantsystem wants 8,4 liter. One needs to be very carefull to make sure that al the clips go in 100% perfekt. From personal experience I can refere to what happandes when the presure builds upp and they don´t. Worst case and it ends upp as a realy hot wet (t-shirt) jobb. (Not in my case) Keep up!

[@SteelJM1]

Leave it to BMW to over-complicate a pretty simple system, with the added bonus of speccing subpar materials so that they break on a regular basis (im looking at you, expansion tank and cooling fan... well basically all of the cooling system plastic). Thanks though for the video, very helpful for fixing my friends car. And from here on in, I'll refuse to do work on VW and BMW from home.

[@dagyiri]

Nice video, what is the name of the last hose you removed before you removed the expansion tank, mine is ripped I believe that’s where my leaking Is from, thanks

[@danielarroyo121076]

Thank you soooooo much help u make it eazy for my life

[@jeremywestwood3769]

Hi Jayson what would you suggest if those upper hose connected to radiator tab so tight i use silicone spray still its very tight that i might break the radiator tab. thank you very much.

[@jenniferscott7582]

Hey 50's kid love your videos! Just wondering if you have ever replaced or know how to replace this part: BMW Coolant Expansion Tank Hose Connector to Mounting Plate 1707817. It is the located on the bottom left corner of the radiator. I have not found anyone, including dealerships, who know how to replace this part. I have the part and am finding it difficult to get the old one off. Thanks in advance! From my husband, Bill

[@lucian1618]

Thanks for the videos do u have any video changing the lines and transmission cooler thanks

[@2ootiehamilton662]

I enjoyed the video and I got to do the same to my 330ci BMW

[@HanhNguyen-ly5pu]

Thank you for the video kids it’s very helpful

[@phucphan9000]

I like to watch your video because of very simple and easier understand Thanks a lot to 50skid. Can you do more on BMW E62 engine V8?

[@50sKid]

Yes I'm going to get to that after I get my engine rebuilt and reinstalled. Need to install valve cover gaskets as well as do the timing chain replacement.

[@Ironfootx1]

Thanks for the video, get rid of that green coolant though dude. You need the bmw coolant in that motor

[@yfi62dortoh]

He used blue coolant

[@carlosverduzco4725]

Great video, Kid! Would this job be considered a full flush, or partial flush? Thanks for the videos. Your step-by-step explanations sure do help the average DIY'er like myself.

[@50sKid]

It isn't any kind of flush. A flush is what I described at the beginning with the machine. This is a fluid change.

[@carlosverduzco4725]

+50sKid ok. I must've missed that part. Thanks.

[@burtfay2335]

Hi no mention of turning the key in possession 2 and too put your heating on and leave for 10 minutes Before starting the car, is it not needed then?

[@ajm9249]

My expansion tank must’ve been on for about 5+ years and It was that bad. But a good way to get leverage and save your back is to take the tank out with retainer bracket

[@codyatkinson]

Question i installed a new expansion tank already has a new pump, thermostat, all sensors changed a year ago. Had no issues just never changed the expansion tank. After installing it I drove the 2000 323i and it keeps overheating. Would it be that I did not bleed it correctly? There are no leaks.

[@donate76]

Thanks for the video! I think i could read that the expansion tank being replaced was manufactured in 2014... so... it was only 2 or 3 years installed in your bmw before you decided to replace it. I am telling this because your hoses came out really easy... that is not as usually happens..

[@paulloper8333]

Crazy huh, if you look at the state of the thing, total garbage.

[@jer3399]

If i replace my expansion tank, upper and lower hoses; do they come with all the o rings?

[@marks878]

In need of a video please. The hose that is on the expansion tank lower part to back of engine I think.

[@TheSanador]

Quick question. I am about to tackel this job on my 330 xi. Do y ou have a good recomendation for where I can get the complete hose kit?

[@EEnsign97]

Any recommendations on when the radiator needs to be replaced? I have a 2001 330i with 135k. My expansion tank cracked and I’m planning on replacing that, all the hoses, thermostat, and water pump. Do I need to replace the radiator as well?

[@robertlaugherty4914]

Great vid. Did this last fall to my 330ci. That trans thermostat always breaks when removing the expansion tank! Know it's off topic but you have any experience on Altima O2 sensor replacement. Evidently a common problem. Thanks and awesome work as always!!

[@50sKid]

O2 sensors are relatively easy to replace. You need an oxygen sensor socket. You should have enough room for this one: www.amazon.com/TEKTON-47749-8-Inch-Offset-Oxygen/dp/B00GMN4D1Q -- Although I HAVE come across an O2 that was frozen in the manifold and impossible to replace... hope that doesn't happen to you!

[@gerardochavez6735]

thanks 50skid i di it save a lots money

[@kennyspringer7668]

Is your threaded drain plug for the new one short or does he go up like the old automatic adjustment screw?

[@CapN-Savvy]

Swapped out my Rad hoses and tank. Filled back up with coolant. Not even half a gallon in, red stick pops up but I have 0 coolant in my top rad hose. Do I keep filling? Or is it all trapped behind my thermostat and I need to get that open?

[@TheCowgirlNiamh]

I haven't even watched it but I know it's going to be a good video ;) I have a new expansion tank ready to fit lol I have a list of things I wanted to get through this summer on the E46 but, this is Ireland, it rains and I have no garage to work in ... Pain in the arse!!!

[@50sKid]

You guys need a big shade umbrella or something!

[@TheCowgirlNiamh]

We need a stealth, pop up garage lol

[@19smiley25]

For the level of collant, do I go off the level with radiator cap off with bleed screw on or with radiator cap off and bleed screw off? Both give me different readings and I already poured 2 gal of 50/50.