E39 BMW 540i 88C Thermostat Install DIY (Cooling Overhaul Part 2 of 5)

Thermostat: click.linksynergy.com/link?id...
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Part 1, I replaced the Expansion Tank
Part 3, I upgraded to an Electric Cooling Fan
Part 4, I replace the Radiator
Part 5, I install a custom aux fan
The E39 has a very complicated electronic thermostat that runs at a very high temperature, and this cause parts to fatigue and fail earlier than they should. BMW realized this and didn't use the same thermostat on the successor to the M62B44TU, the N62B44. This thermostat from ECS Tuning is essentially the one from the 4.8 X5.
This thermostat is a direct fit requiring zero modification to anything. It's as easy as it can get; just disconnect the old one and install this one. It has been working great with zero issues. The car now lives at about 190F-195F depending on speed and traffic. I also didn't get any check engine lights. I highly recommend this.
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[@350Z247]

Still no check engine light. This has worked perfectly with never any overheating even in heavy traffic.

[@trevzor4242]

I just wanted to say thanks for making these videos. They're so informative and you're one of maybe 3 channels who consistently uploads videos on the e39. A+ content, keep it up!! Subscribed

[@350Z247]

Thank you! That really means a lot! I'm glad I can help.

[@trevzor4242]

@@350Z247 Oh, also I've been meaning to ask... Is part 5 of the cooling overhaul on its way?

[@350Z247]

@@trevzor4242 yes, alternative aux fan

[@350Z247]

Part 5 just launched!

[@adnanporobic4989]

Great video, thank you. Subbed.

[@350Z247]

Thank you. I'll forewarn you I sold the E39 years ago, but there are tons of videos on it across several playlists.

[@Rtario]

Yes and your right! Just have to wait for mine now.. Btw where im getting mine they have 80c or 87c or 75c which do u think would be good?

[@350Z247]

I would go 87C just because I have had such good luck with my 88C thermostat. I can't really comment on the cooler stats as I haven't tried them. They may be fine, but they may throw a code. I have a 68C stat on my 350Z but stock is only 78C though.

[@Titansilber.540i]

Do I have to do anything in the DME (M62TU) to make it work properly? I installed mine a few months back, as my old original one got stuck and made one of my hoses pop, leaving me stranded. Since then, I put the 88c thermostat (from an e38 740d), isolated the plug (btw before I isolated the t-stat plug, the car would idle erratically and stall the moment I touched the plug, any idea why?) and I also decided to not put the fan clutch back on, relying only on the aux fan for cooling. During the colder months (10-15C ambient temps) it ran great, around 90-93C and up to 95C when I give it the beans, and then dropping down to 91-93 again. Now that it's a lot warmer (25-35C ambient temps) it usually stays in the 94-96C range and when I push it, it goes to 99-100C and can go well over 105C if I keep pushing it. I know the obvious solution would be to put the fan clutch back on (or install an electric fan, but that's a bit pricey for me), but would driving like this be a problem, as I drove for awhile, with the temps reaching 108C max? Would changing up anything in the DME, like when the aux fan kicks in have any effect? We also have 4 seasons here, with the summer getting to like 35-39C ambient temps, which doesn't last more than a month or two.

[@350Z247]

I wouldn't run it that hot for long; it will wear out plastics and rubbers. Ideally, I would add back the fan if you can't afford to do the electric fan.

[@DriftEmigrant]

Do you know if X5 4.6is is any different that other M62TU , I mean the thermostat housing?

[@350Z247]

The vehicle list for the part doesn't show any E53. However, I'm assuming it would fit. Take a look at your thermostat and see if they look similar. Worst case, you order it and compare them side by side and then return it.

[@jackonbord9149]

Hello Thanks for the info I have a question. Did you change the raditor cap?

[@350Z247]

I didn't, but it was on my list of things to do. The E30 1.4 BAR expansion tank cap will fit the E39 tank if you want a lower pressure cap. Someone also makes a 1.2 BAR cap, but I can't remember who.

[@shaksahim]

Thanks for posting these videos with added details. I'm new to all this and have a 01 540i. I'm changing the thermostat to the 88c one you linked. Is it absolutely necessary to convert to an electric fan or can I leave the clutch fan as is? If I leave it as is, does it make the switch to the 88c tstat useless?

[@350Z247]

No problem! You don't need the fan; it's just good insurance for a likely future failure. The 88C will help keep hoses and plastics alive; it shouldn't be effected by the fan.

[@shaksahim]

@@350Z247 thank you much for the quick reply. Much appreciated!

[@killeracz]

I have a 01 540i as well m sports , after I installed the 88c thermostat I've been getting p1643 code having engine failsafe popped up which I assumed affect rough gear shift and caused a few more incorrect gear ratio code. any chance you got any codes like that linked the 88c mod

[@createbad]

Do you know if it matters what year x5 you get a thermostat from if I want to go that route first instead of buying one? or can i just get an m62tu thermo? Thanks!

[@350Z247]

Lorenzo G. I looked into that for a while then I just decided it wasn't worth it. The price difference was too small to bother so I never figured out exactly which X5 thermostat to use

[@createbad]

350Z247 thanks what about using a newer thermostat from a newer 540i I have a 97 540i. Or you saying I should just get the cooler running thermostat from ecs or a normal thermostat that's made for the 97 540i? Thanks!

[@350Z247]

Lorenzo G. I changed mine because I don't like the computer controlled high temp thermostat. The X5 went back to the normal style, lower temp stat with the next iteration of the engine. The lower temps save wear and tear in the engine and engine bay

[@bdhd206]

per Bentley purge the system with the bleed screw open, car off, radiator cap on, heater on 90" which runs the recirculating pump.

[@350Z247]

Thanks. Always good to learn the other ways to skin a cat.

[@theamerican7080]

@@350Z247 The correct way...lol

[@350Z247]

@@theamerican7080 My way worked. No complaints here.

[@m5p944]

That’s correct

[@slickridley]

did you replace your factory hoses with silicone hoses?

[@350Z247]

Nope, but it would be a good idea

[@bradenclark1560]

Should I do this for my 530i's i6, or does it run at a lower temperature from the factory?

[@350Z247]

The I6 doesn't have the same issues

[@bradenclark1560]

@@350Z247 Great, thanks for your quick response!

[@upbeatgfx1119]

I am about to install this thermostat, What temperatures does you car stay at while idilding after driving ? what did you do with the heating wire that connected to the original thermostat now that this one has a block off. Thanks!

[@350Z247]

I just covered the plug with electrical tape and tucked it under the intake. The car runs at 192 degrees when driving on the highway and sits between 200 and 210 depending on how long I have to idle. The electric fan can keep it at 200 degrees for a good amount of time though. Been like this for months without issue.

[@upbeatgfx1119]

thanks for your response. Im currently having problems, I installed a electric fan and i can drive for a while but after i drive on the highway and go to city driving I hit temps of 107-117c (almost overheating) its a 2500 cfm fan should be fine. Im wondering if the thermostat is sticking. should i try the 88c while im at it?

[@350Z247]

@@upbeatgfx1119 yes, if you're going to replace it, I would go ahead and upgrade. How's your radiator? When is the fan set to come on? How's your water pump? Does your aux fan work? Could be several things causing the issue but thermostat is a good start.

[@upbeatgfx1119]

The lines are hard when car is hot. The aux fan is loud as all hell so it turns on. still not sure whats going on. Someone told me to get a pressure test.

[@upbeatgfx1119]

did you also notice and decreases in MPGS?

[@miketunney9422]

Do you use any RTV on the thermostat when installing or install dry with just the gasket?

[@350Z247]

Just the gasket is enough

[@miketunney9422]

@@350Z247 Thanks!

[@350Z247]

@@miketunney9422 good luck!

[@anthonyk]

Fun fact 88c thermostats were used in the M67 740d

[@350Z247]

That may be where the aftermarket unit comes from

[@hanswurst2161]

how did you hack the thermostat wires plug? actually you'll get an error code if the sensor doesn't get information by the thermostat, don't you?

[@350Z247]

My car was a 2001 and did not get a code. I just tucked the plug under the intake manifold. Drove it for a year like this with no issues.

[@350Z247]

@@Al-hn7gg Good luck. I'm about to do a similar mod for my wife's X5M as it too has a 105C thermostat.

[@user-su8xv8lr4s]

Cool thermo! Do you think it's possible if i use it on my Range rover M62TU engine?

[@350Z247]

Yes, it should. I would compare parts before you swap them, but it looks like others have done it.

[@user-su8xv8lr4s]

@@350Z247 definitely i will take your advice. Thanks man 👍

[@ohnas42]

Thanks for the video, but I'm pretty sure this mod only works on M62TU and not M62. I'm having a heck of a time finding a low temp thermostat for my 1998 540i.

[@350Z247]

It would appear you are correct; HOWEVER, if I were you, I would still order one and try it. The thermostat housings look almost identical other than the angle of the barb and the fact that it's designed for the push-lock style hose. It should bolt up to the block no problem and your standard hose should still slip over the newer style barb. Worst case scenario, you return it. You could even order the new style house and combine the new hose and your old house with a joiner.

[@mikespeksnijder8650]

For an non vanos m62, use a thermostat and housing from an 740i with m60 engine

[@350Z247]

@@mikespeksnijder8650 Thanks for the added info

[@larryjohnson8168]

Couldn’t u take it out of the housing and put in a m62 thermostat housing?

[@stayedsolidtv]

how do you wire in the resistor?

[@350Z247]

What resister?

[@derrickg5612]

Has the service engine soon light come on? I did one of these in my 540 and it keeps throwing a DTC.

[@350Z247]

Mine has not but it seems to be random on which cars will and which won't throw a code.

[@derrickg5612]

I came across your electric fan video because I'm getting read to do one. I've got a video on how to replace the seat leather if that's ever a project you get into.

[@350Z247]

Derrick G thanks man. Mine is in pretty great shape minis the left side of the driver seat. It's had a hard life ha

[@ezzaei]

I got the kit and it states if it throws a light you might have put led load resistor in 10ohm 100w and the ecu will think the pre heated element is still connected

[@derrickg5612]

@@ezzaei Thanks! I may try that.

[@kamikazee3071]

Would this thermostat fit the 1998 e38 with the same m62 engine?

[@350Z247]

It should yes. The ECS website has a list of which vehicles it will fit on.

[@kamikazee3071]

350Z247 alright man thanks! I will make sure the use the link in the video description to purchase one

[@350Z247]

@@kamikazee3071 appreciate it. I loved having it on my car and just did a similar mod to my wife's E70 X5M

[@Rtario]

Hey bro! I just got my ECS Tuning 88c thermostat and it doesn't fit! Man im so disappointed! My car year is 10/97.. weird right!. I called ECS TUNING And they just gave a return label.. They didn't even ask why or what year model was my car.

[@350Z247]

But it's still a 540i? What year range did it say on their website? It bolted right up for me, no problem. Glad they're taking the return though. Sorry to hear it man

[@Rtario]

On their website it stars from 09/98. But I found it elsewhere in Europe though. Next will be the fan once I get the thermostat.

[@350Z247]

R Tario yeah I love having the lower operating temperature. Saves the plastics and the hoses

[@Dannywaffels]

R Tario they changed the hose connections in 1999 you have the wrong part Eva only sells a lower temp thermostat for 99 cars and up

[@anthonyk]

do you think my 2003 BMW X5 4.4 would get pissed at me because there is nothing plugged into sensor

[@350Z247]

My car didn't mind one bit; but others have reported their car threw a code.

[@anthonyk]

@@350Z247 would the car run tho would it be ok

[@350Z247]

@@anthonyk mine did

[@anthonyk]

@@350Z247 ok this should help with the timing guide issue too right?

[@350Z247]

@@anthonyk At this point, no. They're 20 years old by now; doing this would help the next set you put on though.

[@sativa6507]

Do you recommend these parts because they sponsor u or it’s your choice?

[@350Z247]

The main thing is they are the only direct bolt on 88C thermostat for the 540i that I am aware of, but to answer your question, because I chose it. They weren't my sponsor at this point if I remember correctly.

[@upbeatgfx1119]

Do you have the link to the thermostat?

[@350Z247]

Upbeatgfx www.ecstuning.com/b-vemo-parts/thermostat-with-gasket-88c/11512248542~vmo/

[@upbeatgfx1119]

thank you, my radiator keeps blowing up. bought a new one 2 months ago and it blew yesterday. Can that be because of the heat of the stock thermostat? not sure what to do. although, I need to check where it blew this time. Not sure if it was the plastic again or the hose.

[@350Z247]

Upbeatgfx sounds like you just got a bad replacement radiator. The lower temp thermostat will help though as you'll run at lower temp which will also cause you to run at a lower pressure.

[@piotrchodorowski6135]

hi, does this thermostat fit also by m62b44 non vanos engine?

[@350Z247]

As far as I am aware, they are the same thermostat, yes.

[@MrKginter]

A czemu czujnik tak wysoko a nie powinien byc niżej.

[@350Z247]

temperatura jest ustawiona na wysoką, aby zwiększyć wydajność i zmniejszyć emisję; jednak części ulegną wcześniejszemu zużyciu.