overheating E30 325i M20 1986

[ricointheuk]

Hi

We have an E30 325i 1986 M20. We use her for track days. After about 2 - 3 laps she dumps all her coolant out of the expansion tank. We have changed the tank and the cap with no improvement.

Example:

race 2 - 3 laps and the temp is fine and then suddenly goes straight into the red as she dumps the coolant. We then drive slow back to pits and by the time we get back she is back to normal temp. Our friend that comes with us also has an E30 325i 1986 and drives as hard and has no problems his gauge stays halfway to 3/4 max.

fan turns.
oil is clean.
when sat still she is fine.

Want to see our track goddess, check her out here (pic's and video under top left picture of us):

http://www.myspace.com/142861171

Any help appreciated

Richard[/url]

[k10]

Beat me too it, yes any helpo would be appriciated, It doesnt appear to be the head gasket as no mayonaise in oil or oil in water, but who knows??

[SCOTT325SE]

its an airlock in the coolant system guys. you need to bleed the system down. getting a stubborn airlock out can be a pain in the arse.

[ricointheuk]

its an airlock in the coolant system guys. you need to bleed the system down. getting a stubborn airlock out can be a pain in the arse.

Thanks Scott Is there any way to tell if we have removed the airlock as the car is not insured etc so its working out to be expensive testing at track days!

Thanks
Richard

[Brianmoooore]

Check the small tube from the top of the radiator to the neck of the coolant bottle is clear.

[ricointheuk]

Check the small tube from the top of the radiator to the neck of the coolant bottle is clear.

Thanks done that and it is. I assume that you mean that could of been the problem and not, that's how to check we have removed the airlock.

thanks
Richard

[chief]

isn't there a little bleed screw on the thermostat housing ????

someone once said to raise the side of the car with the water bottle(front passenger wheel) so as the water bottle is at the highest point of the water system. then run from cold till thermostat opens. then airlock should be gone.

someone should be along to confirm or condemn these tips. but they have worked on various cars for me,

good luck m8

[ricointheuk]

isn't there a little bleed screw on the thermostat housing ????

someone once said to raise the side of the car with the water bottle(front passenger wheel) so as the water bottle is at the highest point of the water system. then run from cold till thermostat opens. then airlock should be gone.

someone should be along to confirm or condemn these tips. but they have worked on various cars for me,

good luck m8

Thanks for reply chief

We have tried bleeding with the bleed screw as you mention and just got lots of fluid and no air. Instead of jacking the car we removed the expansion tank from the car and held it up high. We should try tilting the car as that may release an airlock problem area.

Can anyone explain to me the mechanics of why an airlock makes the car blow out it's coolant when driven hard.

Thanks
Richard

[Chris-W]

Because it stops the coolant from circulating until it boils!

Holding the expansion tank up[ won't help, you need to raise the car to encourage the air to move towards the front of the engine.

Does your heater blow hot air?

[ricointheuk]

Because it stops the coolant from circulating until it boils!

Holding the expansion tank up[ won't help, you need to raise the car to encourage the air to move towards the front of the engine.

Does your heater blow hot air?

Hi Chris

The heater has had all the knobs removed as we have no dash board. I will connect up the controls and check.

Thank you for the explanation of what the airlock does. When the car is sitting still and idling with the airlock we should get no circulation(If I understand you correctly). Now, we have had her idling and the cap off the expansion tank and the little tube that goes back to the rad has water pumping through it, out in to the expansion. Would that suggest that we do have circulation? (please remember that I am no mechanic and might say things that are incorrect or even stupid!)

Thanks for help

Richard

[Chris-W]

It's like a baby with trapped wind, sits happily for a while, then all of a sudden......

Good sign you have got rid of it (with cars) is that the heater is blowing good and hot.

[BreadBin]

You need the heater set on fully hot when bleeding the cooling system.

[ricointheuk]

Thanks for the help all

We will try the things you have said and let you know how we get on.

Thanks
Richard