1998 323is E36... overheating mystery

Tony Rockwood · 06:16 PM

I have a 98 323is with 94,000 on it. Blew the radiator up at 75K and replaced it, the thermostat, the thermostat housing (aluminum now), water pump (metal impellor now). The head eventually proved to have been warped but I fixed it with a can of Bar's head gasket repair. It worked, no smoke, no loss of water and it ran fine until... The radiator blew again. Actually it has blown up 3 times in the past 3 years. It has been replaced for free do to the warranty however they won't refund me. And yes it has plastic end caps and that's where it blows up. That however is NOT the problem.
I have bled the system a number of times but I still have overheating problems out of the blue. NO smoke coming out of the tail pipe, no leaks, water level staying constant, checked thermostat and its working fine, fans seem to be ok so... I have drove all over LA on a 100 degree day with no issues, get in the car the next day and run down the street and it gets hot... any idea what could be causing this?

Luccia at Pelican Parts · 10-19-2016, 11:25 AM

Any codes present in the system? You might be able to pressure test the cooling system to see if it might show signs of what the culprit may be. A local BMW indy shop can do this or you can do it yourself. You attach the unit to the coolant tank and then pressurize the system.

Pressure Testers - PelicanParts.com

bmwbeemer7 · bmwbeemer7's Garage

Did you make sure to remove ALL the air from the system since it did run hot? They are known for holding on to air after running hot and it takes a special procedure in order to remove all of it to prevent overheating in the future. Hope this helps.

Tony Rockwood · 10-19-2016, 06:03 PM

I have bled the system and it still does it. I actually just circumvented the heater core thinking it may be clogged do to the Bar's stop leak. Now the check engine light is off and it seems to be running fine. I'll know more the more I drive it.

Luccia at Pelican Parts · 10-20-2016, 08:37 AM

Even though the light is off, I'd still plug in and read what fault code is stored. May have an intermittent issue at foot.