E34 535i getting warm

Hoping to find a solution here, i'm a new member but have always read through the forum for advice in the past...

Bought my new baby nearly 3 weeks ago and hadnt had a problem until the other morning driving to work, i noticed it took a long time to warm up. i have always owned e34's, from my 1st 520i, my 525i and my M5 in ireland. this is my 1st aussie girl and shes sweet as a nut but a little bit moody. anyway, i noticed it took a while longer then usual to warm up and then at traffic lights went slightly above the middle mark on the temp gauge. once i drove it went back down, but now its doing it more and going up as far as 3/4 on the gauge.

ive read through different threads for pointers.. i am a mechanic, though not BMW, but i have checked everything i could think of and have read about. there is still some air in the system, it had a new rad at some stage before i bought it, but never gave an ounce of bother until 2days ago after having it 2weeks... any suggestions?? i dont think its head gasket related...

cheers dudes

Hi from Perth!! Thermostat! PM me!

Thermostat would be what keeps it from warming up properly. Getting warm at a standstill could be a bad fan clutch.

Not sure of the capapcity, but between the radiator, overflow tank and heater core, our cars hold a lot of coolant. Thermostats seem to get old and open slower than they should, found that out when my Volvo was slow to warm up, new thermostat now and it gets to operating temperature very fast.

With the way the temp is erratic I'd go for the t'stat first as it is past it's use by date any way. My e23 failed closed after a lot of erratic up and down.

Cheers men, by the looks of the engine it's been looked after by the po but maybe because it had never given trouble the thermo was never replaced.. It's a cheap part I'll try get one for the weekend an let ya's know

Don't get a cheapie - go genuine - or at least get it from Lintrex.

Originally Posted by BMWFatherFigure

Don't get a cheapie - go genuine - or at least get it from Lintrex.

for the record, genuine are cheap. i replaced the one in my E30 for $30NZ (about $15-20 US

Originally Posted by _Ethrty-Andy_

for the record, genuine are cheap. i replaced the one in my E30 for $30NZ (about $15-20 US

I'm in Western Australia where nothing is cheap Just been to my local dealership, $54 for the Thermo and $6 for the O-Ring.. Not too bad i suppose... If its keeps my eyes on the road, an the women on the footpath, instead of the temp gauge then its worth it...

Its definitely not the HG, i drove the stones out of it on the way home from work and the temp didnt budge from where it's supposed to be! great success!!

Originally Posted by DanM5

I'm in Western Australia where nothing is cheap Just been to my local dealership, $54 for the Thermo and $6 for the O-Ring.. Not too bad i suppose... If its keeps my eyes on the road, an the women on the footpath, instead of the temp gauge then its worth it...

Its definitely not the HG, i drove the stones out of it on the way home from work and the temp didnt budge from where it's supposed to be! great success!!

Thats still pretty reasonable. even Corolla's arent much cheaper than that

Right gents, replaced the thermo, flushed the coolant and replaced with genuine coolant, bled the system, alot, and it's still getting warm!! In fact it's getting worse.. I'm thinkin it the fan so I've ordered a fan clutch!! In the meantime I need to keep her cool but still need to drive it everyday.. I need help... Suggestions???

When is it getting warm?

Getting warm while in traffic at low speeds is an airflow issue, often the fan clutch or aux elec fans not coming on. There is a test procedure in the Bently manual for the fans.

Getting hot running down the open road at highway speeds is more often a water flow issue and the water pump is usually the culprit.

Are the radiator fins clear? Sometimes you can accumulate debris between the AC condensor and the radiator. Make sure the airflow to the radiator is not somehow blocked. Usually a good garden hose flush from the back side gets rid of most of the junk, or use compressed air. Just be careful not to use enough pressure to bend the fins in either case.

Both, hot while driving on the highway and sittin in traffic!! I wired the aux fan to stay on constant at low speed to see if that would work, it helps it by taking longer to get hot but it still gets too hot for my liking! I have wired it now to stay on at high speed so I will see on my drive home from work if this helps.. The rad looks brand new, but I'll blow it out just to eliminate that problem.

What's happening is so strange given that I only bought the car a month ago and for the 1st 2weeks it never missed a beat... Bentley explains about the temp sensors but I wonder if the sensor was faulty would it read the temp too high, Bentley basically says if the gauge is reading in the middle with the engine at operating temp and the sensor unplugged then the gauge is faulty and if the needle drops once the sensor is unplugged then the sensor is ok...

I say the rad looks new, it's either new or was off and checked and sprayed black.. Would the paint on the fins prevent cooling, it had crossed my mind but like I said, the car was fine for the 2weeks after I bought it...

New fan clutch
New thermo
New temp sensors
New coolant
New rad cap
New water pump

Still overheating!!!!!! Interior fan blowing hot so don't think it's trapped air, or h/g, have the aux fan wires jumpered on high at all times, but, it's still getting too hot.. Only thing left is a rad or a blockage somewhere!! I'm in dire straits here men.. This car is my everyday driver!! I get half way to work and it heats up, so I pull in for a minute or 2 an switch it off.. Switch it back on an the gauge immediately drops to half way and I carry on to work.. By the time I get there is hot again!! I'm summoning all of your combined wisdom here gents....

What tipped me off was the "painted black" radiator. This is what my newer radiator looks like.




I am pretty sure that it should be raw aluminum, unless they changed over the years. I wonder if the PO tried a cheap fix on the radiator? Just because it looks new, doesn't mean it is new, or working properly.

You have done everything else... bite the bullet, replace the last link in the cooling system chain. Well maybe... since I have a heater core to replace on my car. It is the gift that keeps on giving.

I think I may not have any other option!! Also, I replaced the rad cap, and noticed that the old 1 was missing 2 o-rings.. I wonder if they've broken up an caused me to have a blockage somewhere.. Though I don't think the particals would be big enough to block the pipes completely, would they??

Originally Posted by DanM5

I think I may not have any other option!! Also, I replaced the rad cap, and noticed that the old 1 was missing 2 o-rings.. I wonder if they've broken up an caused me to have a blockage somewhere.. Though I don't think the particals would be big enough to block the pipes completely, would they??

If there's enough crap in the radiator and it went down stream it will slow the circulation if not cause a blockage. Here's my take.

If you replaced:
New fan clutch
New thermo
New temp sensors (there are 3 or 4 I've only seen 3)
New coolant
New rad cap
New water pump

Remember there are 3 maybe 4 temp sensors which go bad on a m30b35
two or three on the thermostat housing.



or



No# 16 is the odd ball for specific models.

And one on the radiator: no#5

Could be have a pinhole leak somewhere or you need to bleed the system some more.

Hopefully this helps.

Mine only has 3 sensors.. I've replaced 2 of the 3, the 3rd is the aux fan temp sensor.. Which I had jumpered and made no difference!! I think I may be drawing in air from somewhere as no matter how much I bleed it I still get air through it.. I just need a good bit of time at this to figure out where I'm getting air in from.. I'll keep ya's posted..!

I think if I were you I would buy or borrow a pressure tester. You can pressurize the system and look for leaks.

Yeah we have 1 in work, I'll take it home this weekend!!

Ok Gents, I'm happy to report that, after a lot of frustration and $$$ spent, my car has finally stopped heating up!! After replacing all the usual suspects, it was still heating up, so I removed the rad and flushed everything separately.. I found that my aux water pump is shot and clogged so I cleaned it up and put it back in for now as I can't afford to replace it yet, rechecked everything and put it all back together, filled it up with BMW coolant, as I had done previously!! It was STILL heating up, and then cooling down by itself.. So I drilled the thermo as suggested by some1 previously to help remove trapped air.. It was still heating up.. But the erratic behaviour of the temp gauge led me back to the Thermostat, as some1 suggested before that even new ones fail.. So I removed the guts of the original thermo and stuck it back in and took it for a spin.. And what dya know, it never once, even when driving hard, went over the half way mark....Result!!! I will continue to monitor it though just incase I'm not out of the woods, but towards the way it was acting its looking good so far!!
Moral of the story, the original suspect was the culprit!! I don't need a thermo in this glorious country so ill do without!

I would just like to thank ya's all for your input and advice, it's much appreciated
Cheers Lads

There are some valid reasons to run a functionl therostat in these cars. Without it, warm ups will take longer. If the car has a catalytic convertor installed, excessive rich mixtures can harm it. You want the car to full warm asap, thermostat makes this happen.

The car was designed to run at a certain temp, the thermostat makes that happen allowing engineers to optomise performance in that range.

I wasn't sure from that last post if you intended to just remove the t-stat... I wouldn't, just get a good working one.

I just removed this morning to rule it out, it was definitely a t/stat problem! I can fit a new thermo now safe in the knowledge that that was my problem.. The climate here is quite warm all year round so the car gets up to temperature quite quickly, but I am of the same opinion as you, if mr. BMW wanted the car to run without a thermo it wouldn't have 1..

I'll keep you posted