Coolant issue only at autocross

[ccarlozz]

87 325is. When I drive around town or on the highway I have no overheating issues, temp gauge is usually at 1/4. Today after my first run at autocross the temp was at 3/4 and I popped the hood to assist in cooling the engine down. With the hood up i noticed that a lot of coolant was flowing out of the expansion tank from the breather pipe. Needless to say I didn't complete anymore runs. Waited a little for the engine to cool and drove it home with no further issues.

I recently replaced the coolant temp sensor and engine temp sensor so I don't think that is the issue. Any ideas?

Thanks

[Jaxx_]

first test should always be the newspaper test for the fan--get the car up to temperature and put folded up newspaper into the fan and see if you can stop it. If you can you need to replace your fan clutch. Otherwise, you should start with a coolant flush and check for any blockages. These are relatively cheap things to do before you replace the mechanical side of your cooling system, the thermostat and waterpump.

[Andy.B]

I have this same issue with slight overheating in my 87 325e at autocross. I've taken to shutting it down between runs when it's up to temp and keeping the heater on when it's running.

Right now I have the engine bay stripped down to convert to late style cooling, swap in a mishimoto radiator, and retrofit the I oil cooler (as well as a few other goodies, like an i head/intake/motronic).

I'm confident the swap to the later style cooling system, bigger radiator, and added oil cooler will help.

[ccarlozz]

Fan clutch is good. Looked under the coolant reservoir cap and saw some brown stuff, very little...I'm thinking oil and head gasket. Am I wrong?