Dreaded cooling system issues

[Neoparoykos]

***I have browsed some other of the old threads regarding the issues but relevant images are dead.

I recently replaced the thermostat housing with a unit from Ireland Engineering after mine was damaged upon removal. The unit is a newer style with a larger t-stat cover that necessitated me swapping to my original (see pictures). In the process I also replaced the t-stat with an OEM example. Not surprisingly, I am having overheating issues. It will rise to just before the red while at a standstill and will decrease to just above the first hash at highway speeds, seemingly once the t-stat opens. I have bled the system sufficiently (I believe), but understand it could be an issue related to newer t-stats with the older cover? Any help would be appreciated.

Note: Auxiliary fan is coming on and engine mounted fan will not spin when the car is off without significant force. Spins properly when car is on.

 

[Stevehose]

Correct thermostat for new housing? Thermostat in backwards? Thermostat tested on the stove? Drill a hole in the edge of the thermostat and mount it as close to 12 o'clock as possible? Bled the system by disconnecting the hose at the overflow tank, connecting another hose in it's place and blowing the air out that way? Definitely frustrating.

 

[Neoparoykos]

Correct thermostat for new housing? Thermostat in backwards? Thermostat tested on the stove? Drill a hole in the edge of the thermostat and mount it as close to 12 o'clock as possible? Bled the system by disconnecting the hose at the overflow tank, connecting another hose in it's place and blowing the air out that way? Definitely frustrating.

I'm unsure how to match t-stat to housing. It installed without issue and the images here on the site from a past post are dead. I have the t-stat pointed like the image below towards the front of the car.

I avoided drilling the hole as I had mixed reviews on its effectiveness on a modern t-stat. Should I do it anyway? Can you elaborate on that bleed procedure?

 

[duct-tape]

if youre running hot at idle and cool down when moving, its could be related to your fan. have you checked that it's turning at all?
if its cooling down when youre moving, then your thermostat is opening correctly, otherwise coolant wouldnt be free-flowing to the radiator.

that could mean that you need to bleed better, or your fan.
with my 735, I had to bleed it by parking on a steep grade. I used a loading dock

 

[Neoparoykos]

if youre running hot at idle and cool down when moving, its could be related to your fan. have you checked that it's turning at all?
if its cooling down when youre moving, then your thermostat is opening correctly, otherwise coolant wouldnt be free-flowing to the radiator.

that could mean that you need to bleed better, or your fan.
with my 735, I had to bleed it by parking on a steep grade. I used a loading dock

Fan is def moving at idle. Weird thing is it seems t-stat opens once the car is too hot, right before "redline."

I'd like to try the bleed procedure Steve mentioned above.

 

[sfdon]

Quit before you ruin your engine.


you have an early thermostat in a later thermostat housing.

you need the later 1990 thermostat

note the “A” on your new housing- it’s there as your warning not to do what you are doing.

 

[Neoparoykos]

Quit before you ruin your engine.


you have an early thermostat in a later thermostat housing.

you need the later 1990 thermostat

note the “A” on your new housing- it’s there as your warning not to do what you are doing.

How can I identify a later t-stat? Does BMW still sell the early t-stat?

Also, any idea how they changed? I'm using an older t-stat cover with the newer housing.

 

[sfdon]

The cover is meaningless

October 1985 the housing and thermostat were changed.

use the Later thermostat with the later housing.


the early thermostat is too long.

 

[Neoparoykos]

The cover is meaningless

October 1985 the housing and thermostat were changed.

use the Later thermostat with the later housing.


the early thermostat is too long.View attachment 104390

Thank you for the info. I'm using 11-53-1-251-041. Is that incorrect?

 

[sfdon]

I believe I just posted a picture with Correct part Number- are you on a Mobil device that doesn’t show it?

 

[sfdon]

I’m driving in to shop now- can’t text.
check out my last post and order that thermostat
it is correct

 

[Neoparoykos]

I believe I just posted a picture with Correct part Number- are you on a Mobil device that doesn’t show it?

I see it now. Thank you.

 

[Neoparoykos]

Returning to this, I am still having issues. I replaced the thermostat with the correct unit and the car is still overheating.

Here's what is interesting. When I bleed the system once more and refill the coolant the temperature will remain around a third. Seemingly where it should be. If I park the car overnight and drive it the following day after work it will begin overheating. If I again bleed the system and refill the coolant the car will run where it should be, around a third. I even tried getting on it as much as possible in an attempt to raise the engine temperature. It always remained slightly below a third or slightly above.

Is it possible for air to re-enter the system as the car is sitting? Someone suggested the radiator cap, but that would mean that the air somehow enters through the expansion tank and passes through liquid, which doesn't seem possible.

Thoughts?

My greatest fear is of course a head gasket or cracked head. The car doesn't seem to be performing any poorer than previously and I do not notice coolant in the oil. I am getting what seems a bit of moisture in the valve cover that shows up on the underside of the oil cap. Is that common or an indication of a larger problem?

 

[Mot27cars]

I’d say you need to do a compression check and or a leak down test.

 

[HB Chris]

I’d say you need to do a compression check and or a leak down test.

I agree, that cap does not look good.

 

[GolfBavaria]

That's exactly what my 2002 radiator cap looked like when I blew my head gasket. It will still run ok for just a little bit, wouldn't recommend driving anymore until you take it to a shop and have it looked at. I'm no mechanic, but that milk chocolate look is usually a bad head gasket, so I am told. Water mixing with the oil and getting hot.

 

[Neoparoykos]

I’d say you need to do a compression check and or a leak down test.

I previously did a compression test and it was normal. A leak-down is a bit trickier DIY I believe?

I agree, that cap does not look good.

A friend, owner of an E9, said it is normal. *shrugs shoulders*

That's exactly what my 2002 radiator cap looked like when I blew my head gasket. It will still run ok for just a little bit, wouldn't recommend driving anymore until you take it to a shop and have it looked at. I'm no mechanic, but that milk chocolate look is usually a bad head gasket, so I am told. Water mixing with the oil and getting hot.

I sure hope not.

 

[Dick Steinkamp]

What you pictured is an oil cap. If it was a radiator cap I'd be VERY worried. If you are sure you are not getting water in the oil, that could be condensation especially if it has been started many times and not allowed to warm up. Change the oil. If it comes out looking like thick chocolate milk, you're in trouble. If it looks fairly normal you're OK.

Running the engine can purge some of the trapped air from the cooling system. If you are now to the point that you have purged all the air and topped off the coolant and it is no longer overheating, you should be in good shape. My Bav temp gauge never gets to the half way point on the scale.

 

[Neoparoykos]

What you pictured is an oil cap. If it was a radiator cap I'd be VERY worried. If you are sure you are not getting water in the oil, that could be condensation especially if it has been started many times and not allowed to warm up. Change the oil. If it comes out looking like thick chocolate milk, you're in trouble. If it looks fairly normal you're OK.

Running the engine can purge some of the trapped air from the cooling system. If you are now to the point that you have purged all the air and topped off the coolant and it is no longer overheating, you should be in good shape. My Bav temp gauge never gets to the half way point on the scale.

Thanks for the reply, Dick. Yes, I think there was some confusion in regards to whether or not that was the oil cap or the radiator cap. It is definitely the oil cap.

The interesting thing is that I have repeated the purge and top off procedures several times only to find that the subsequent day it begins overheating again and acts as though there is more air in the system. Once I purge it again and add more coolant it seems to perform normally. It did this both yesterday and today. I just returned from going outside and starting the car for a bit to let it idle. It idled for 15 minutes or so and remained around one-third. Hoping it stays this way when I get home from work tomorrow.

 

[Stevehose]

I've had that, I think it's a cracked head or blown head gasket