Radiator problem.

[gazwhittle]

Hi guys had a quick search and didn't come across any answer which suited my dilemma.

I recently bought a new 91 316i m40 and it's a great little motor except I noticed the temp gauge was stuck at quarter and upon pulling the thermostat I soon realised it was A: stuck open and B: 77c instead of 88c.

Anyway I changed thermostat, bled the system properly got nice hot heaters and the temp sits just under half as normal, both hoses warm so the thermostat is working as it should.
But I noticed that coolant is coming from the radiator cap so changed it for a new one and same thing.

It only leaks a little bit when at running temp and most times at idle I can see a little steam while using a torch.


Could it be that the system is over filled after bleeding as when hot with the cap off coolant is rite upto the top of the expansion tank. ? I also thought maybe over pressurised from a leaking head gasket but the pipes ain't rock hard.


Btw the radiator is brand new so is the water pump. Any ideas ?

[Brianmoooore]

Does the car keep pushing coolant out until the bottle is empty?

[gazwhittle]

No I had it running for an hour and the level beryl moved. Last night it seemed to be just a tiny bit of steam that I could only see with a torch. But when I drive I do get a tiny leak.

[gazwhittle]

It doesn't boil over or anything like it would if it was over heating.

[Brianmoooore]

There's a good chance you are suffering from the very common condition, known as "E30 paranoia." The system is supposed to push coolant out of the pressure cap, until it reaches its natural level, which is normally about 10mm lower than the level mark on the tank.
Just drive the car and watch the level. No harm will occur until the tank is almost empty.

[Tommek]

Next to the coolant cap is the bleeding screw which should have an o ring .... maybe there you see steam leaking out

[Brianmoooore]

Next to the coolant cap is the bleeding screw which should have an o ring .... maybe there you see steam leaking out

Next to the coolant cap is the bleeding screw which becomes extremely fragile with age.
If you break it, take a small/medium screwdriver, heat up its tip and push it into the remains of the plug left in the radiator. It will melt into the plastic and enable you to easily unscrew the remains.
Replacement bleed screws are readily available from BMW.

[Tommek]

Next to the coolant cap is the bleeding screw which should have an o ring .... maybe there you see steam leaking out

Next to the coolant cap is the bleeding screw which becomes extremely fragile with age.
If you break it, take a small/medium screwdriver, heat up its tip and push it into the remains of the plug left in the radiator. It will melt into the plastic and enable you to easily unscrew the remains.
Replacement bleed screws are readily available from BMW.

+1 ... completely true, i'm not saying that the bleeding screw is the problem ( he says the rad is brand new so it's hard to believe it is ), i just indicated it as a possibility because it's hard to believe coolant will leak at the rad cap as long as the plastic expansion tank is not cracked in that region.

[gazwhittle]

Thanks Brian I did have a feeling it could be over filled. Thanks dude

[gazwhittle]

As said the rad is brand new the coolant and trickle of steam is 100% from the cap. I even removed the plastic plate from the top so I could see the bottom of the bleed screw and cap.

[gazwhittle]

Also failed to mention if I squeeze the top rad pipe I can hear air being either pushed into the expansions tank or out the cap. If I put my hear on the cap it's quite prominent. Again maybe it's just fluid from in from the top.

[Tommek]

Cooling system should be under pressure and operating at about 1.5 Bar .. no steam should escape from anywhere ... change the rad cap or chase the fault elsewhere

[HairyScreech]

Even when correctly filled squeezing the top hose seems to make a squelchy sound, at least on nearly all M20 e30s I have come across.

I think its due to the overflow/rad bleed return entering above the level of the coolant in the tank.

edit - possibly ignore that, just noticed the 316i dose not have a separate expansion tank.

[blazed]

take some coolant out sounds over filled, shud have a few inch gap to the fill level.

[Brianmoooore]

There's no need to take any coolant out. It will continue to push coolant out of the cap (as it's supposed to do) until the coolant level in the bottle stabilises, which should be just below the mark on the tank.

[gazwhittle]

Well good news checked coolant and it's at kolt now. Fired it up with no signs of leaking.

But why I'm here im int the process of checking various sensors. Should I hear the TPS click twice ?

[Brianmoooore]

Should I hear the TPS click twice ?

No. There are two switches inside of it, but only one is of a type that clicks.
Lack of a click only proves that the TPS isn't working. A click doesn't prove that it is.