Another cooling problem

[Entropyman]

I have a cooling issue. My car (97 318Ti) has been overheating. I researched this site and found that the issue was most likely air in the system. I have a question about the bleeding process. When I follow the Bentley procedure and I fill the the overflow tank until coolant flows out of the bleed hole, the overflow tank is completely full past the “max cold” line. The procedure does not mention removal of coolant back to the “max cold” level. Should I do this? Also, when the engine is cooling, there is a hissing/ bubbling sound coming from the radiator cap. Does this indicate a faulty radiator cap? I am trying to determine why air got into the system in the first place as there are no obvious leaks, the system has not been opened recently and there are no indications of head gasket problems. Sorry for the long post and thanks for any help.

[DueceMcCracken]

What exactly did you check?

I would check coolant for signs of oil
Oil for signs of coolant
Constant loss of coolant usually mean bad news.
Run your car to operating temp then shut her off and then open your oil filler cap and look for steam,
Check the color of your exhaust smoke.

Check all hoses and plastic coolant fittings for signs of leakage!

I just blew the hg in my 98 Ti. All my coolant was going into my oil. No other signs. Sucked big time.

[Entropyman]

I thought I had it today. I did another bleed using the procedure from understeer.com and finally got some warm air out of the heater. I changed the radiator cap and the hissing/bubbling sound went away so I thought it was good. Tried to take it to work and it started overheating again. The exhaust is not visible and smells normal, there is no foaming or steam under the oil filler cap and the oil level hasn't changed since I change the oil about 1000 miles ago. I'll mess with it some more tommorrow but I'm kinda at a loss. Thanks for the response.

[L84THSKY]

Bad thermostat possibly.

I thought I had it today. I did another bleed using the procedure from understeer.com and finally got some warm air out of the heater. I changed the radiator cap and the hissing/bubbling sound went away so I thought it was good. Tried to take it to work and it started overheating again. The exhaust is not visible and smells normal, there is no foaming or steam under the oil filler cap and the oil level hasn't changed since I change the oil about 1000 miles ago. I'll mess with it some more tommorrow but I'm kinda at a loss. Thanks for the response.

[nyle]

The bleed method in the manual seemed pretty vague to me. It says unscrew the little bleed cap and run the heater on high until no more bubbles come out. i didn't have bubbling, just steam but it seemed to work.

what i did though was fill up to the max, and leaving the coolant reservoir cap off, i unscrewed the bleed cap a bit and ran the heater. it seems like if i poured more coolant in during that process the pressure would push it through the system a bit. it sucked in a lot more coolant than i was expecting. (I had the little Y-shape connector on the back of the head break, so I lost it all pretty much).

[zboot]

The bleed method in the manual seemed pretty vague to me. It says unscrew the little bleed cap and run the heater on high until no more bubbles come out. i didn't have bubbling, just steam but it seemed to work.

what i did though was fill up to the max, and leaving the coolant reservoir cap off, i unscrewed the bleed cap a bit and ran the heater. it seems like if i poured more coolant in during that process the pressure would push it through the system a bit. it sucked in a lot more coolant than i was expecting. (I had the little Y-shape connector on the back of the head break, so I lost it all pretty much).

You should be doing this with the car cool. If you're getting steam, the car is way too hot.

Also, if you're getting steam coming out when the engine is running and everything is closed up, you may want to consider running some coolant leak sealer through your system.

[CirrusSR22]

I don't think the procedure in the Bentley does a thing :) I've used the understeer.com procedure a couple time with success. Having the RPMs up near 2500 while the bleed screw is out seems to be the trick. Idle doesn't do a thing for me. Make sure you have someone watch the temp guage while you do it. It should never get above halfway during the entire process. And yes, steam is bad!

[dave45056]

This could also be a water pump problem. You've heard of the notorious plastic impeller?
I would replace both the thermostat and the water pump if it was me.
This can turn into a HG problem (if it isn't one already) if you are not careful.

[Entropyman]

I have ordered a steel impeller water pump, thermostat and hoses from Autohaus AZ. I will park the car until I change this stuff. Thanks for all the replies!

[BMW_318TI]

Yeah just unscrew the little bleeding screw and start the engine.
I didn't have bubble too only steam, but temperature gauge is the in middle:-).

[Entropyman]

Pulled everything apart Saturday. The water pump had a steel impeller and looked like it was in decent shape. When I drained the radiator I didn't get more than a quart of water and it looked like it didn't have any antifreeze in it. I did not pull the engine drain plug, I'll do that when my new parts arrive. My plan now is to get everything back together, get the whole system leak checked, run a compression check and go from there. Any other suggestions?

[JNCoulombe]

If your overheating problems persist after replacing the waterpump and thermostat consider replacing the radiator.
I just replaced my radiator after replacing everything else. It wasn't nearly as expensive as I would have thought ($200 from Bavarian auto) and it wasn't very hard for me to do. I could not get the low speed fan to come on and would therefore overheat on hot days, but only when stuck in traffic so I had assumed the radiator was okay. I had had a bad fan switch but even replacing that and making sure all the electrical circuits were okay I still couldn't get the switch to close when installed. Mostly the car would not get too hot when I turned the air conditioner (and therfor high speed fan) on or when running at speed. Finally on a very hot day I overheated dispite the highspeed fan and running at highway speed. I had a shop check for hydrocarbons in the radiator and do a pressure leakdown test which indicated that the head gasket was okay so with nothing remaining to blame it on I replaced the radiator. There must have been a partially clogged radiator that didn't let enough hot water get to the switch but otherwise usually seemed to allow sufficent flow. Now seems to cool okay.

[Entropyman]

Thanks for the input. My radiator is supposed to be new but I didn't buy it myself and right now everything is suspect. Does anyone know if there is a way to check a radiator for proper flow?

[Entropyman]

I think I have found my own method to verify proper coolant flow through the radiator.
After changing the water pump, thermostat, and both radiator hoses I successfully bled the system (proper amount of coolant in system, no bubbles and good hot air from heater). The car still overheated after a short drive. I removed the front shrouding and the electric fan to give me access to the radiator. I then warmed up the car and put my hand on the radiator to feel for differences in temperature. I used a kitchen thermometer to measure actual temperatures. When the engine was about 170 degrees (measured on the block) about 80% of the radiator on the intake side was warm to the touch but not hot, the rest of the radiator was HOT. This was an area about 4" high, and about 3" from the bottom of the radiator on the intake side. I used my thermometer and found that this area was 50 degrees hotter than the area around it. The conclusion I draw from all this is that this is the only area that coolant is moving through properly and the radiator is substantially clogged. New radiator time.

[nyle]

good thinking. keep us posted.

[Entropyman]

New radiator arrived yesterday, a Behr from eeuroparts on ebay, $149 with free shipping and arrived in 3 days from Connecticut. I installed it today and the problem is solved. Frustrating that it took that long but I'm glad it wasn't a head gasket.

[nyle]

sweet deal. :)