Still Hot

[fenhow]

First, Thanks to everyone who has contributed to my problem.
I have a 96 525i it started overheating last week. So far I have done the following;

Thermostat - replace from BMW
Water Pump - replace from BMW Metal Impeller
Radiator Check - OK
Coolant Flush and replace
All fans working

Now, my car will run normal for about 10 minutes, when I rev to about 2Krpm
for 2 minutes i start to get trouble. The temp gage bounces sporaticly between normal temp and hot. I get the infamous bing and check coolant level shows, or I get the overheating warning. When i rev the engine the gauage goes back to normal operating temp.

I note a lot of bubbles and water bouncing in my overflow tank. A lot of steam from my pressure valve when I loosen it.

I have removed all of the hoses, including the ones on the heat exchanger and flushed the system to its entirety. Water flows.

I am asking if there are any other possible fixes to this problem before i have to take the head off. If it does need a head gasket or head (heaven forbid) is that the kind of job for a do it yourselfer? and does anyone have a link to instructions on how to?

Thanks In Advance,

Fen How

[Dan in NZ]

Head Gasket. Could've saved a whole lotta trouble if you fixed that first...

[Springfield1952]

If it's a head gasket you'll usually have one of two telltale signs. Either there will be oil in the coolant water which you should be able to see in the overflow tank since oil floats on water or there will be water in the oil. This can be checked by looking at the dipstick which will have a chocolate milk like coating from water whipped into the oil.

As for a DIY project, I'd rate it a four out of five wrenches in difficulty.

Good luck.

Curt.
1994 530iT

[fenhow]

Thanks, however no signs of oil in the coolant or water in the oil.

[Paul D]

You can check to see if you are loosing coolant by pressurizing the system. This is done with a small hand pump with the engine off (most shops have this tool). Look for external leaks first, if none, try removing the spark plugs and oil filler cap and listening for noises from the crankcase or cylinders. If there are noises there you’re in for the 4-5 wrench DIY job! It does seem that with all of the bubbles you may want to do a thorough bleeding of the system. What can I say, I’m an eternal optimist!!!

[bimmerd00d]

i really dont think you're bleeding the system properly. Make sure the car is cold when you start this.

1. take off radiator cap.
2. top off the coolant tank
3. open the bleed screw, it's right next to the radiator cap, dont have to remove, just loosen it about halfway.
4. Start up the car, turn the heater on full hot, medium fan speed
5. coolant will begin to come out of the bleed screw, as well as air bubbles.
6. Let the car reach normal operating temp before finishing this procedure
7. Make sure to add coolant to make up for what comes out of the bleed screw.
8. You might have to do this 2-3 times over the course of a week to get them all out.

Hope that helps, it's sort of a last resort before the head gasket. I am not sure if you already attempted this. Good luck!

EDIT: Also, when your car reaches normal operating temp, the coolant level may go down as the car is sucking it into the water jackets. Make SURE you add coolant to compensate, and keep a close eye on the temp gauge as the coolant level goes down during this. If this doesn't work, you may have a faulty thermostat, sometimes they ship a bad one. Basically you can troubleshoot a bad t'stat, by when the motor gets to normal operating temp the coolant level in the tank never changes and the car then overheats.

[western99]

Make sure that you let the coolant run from the the pressure screw on the rad when bleeding. Then tighten it as it comes out. When there is a steady flow of coolant coming out, that is when you know that you have bled the system properly.

Brian