Running Hot At Low-speed/idle

[Dozer]

Hello all,

I have a 95 325is and the cooling system is driving me crazy. I have read a lot of back posts re: overheating and they have been of some help but I still can't narrow it down. Here's the situation:

Car was kept by my dad for the last three years and driven very little. He had a new radiator put in while I was overseas. Drove it cross-country when I returned to the States this summer with no cooling problems except a lack of heat when I needed it in Breckenridge, CO! Got it home and found that it wanted to overheat in our bumper-to-bumper San Diego traffic. Drained the fluid from the radiator only (couldn't find the engine drain) and proceeded to refill the system, being careful to refill with the heater, get the air out, etc. It eventually took over 3 gallons of coolant mixture (did not use original BMW coolant). Also replaced the coolant level sensor in the expansion tank b/c I'd been looking at the "Coolant Level Low" message for 4 years!

So, things seemed normal for a while, and now at normal driving speeds it runs at normal temperature. However, when traffic slows to a crawl or the engine idles for a while, the temp level starts climbing up, and sometimes hits red. When it does hit approach red, getting off on a side street and ramming air into the front end will bring it back down. It'll run normally in normal traffic after that. Oh by the way, the "Coolant Level Low" message is back with a brand-new sensor in, and the coolant level in the expansion tank is filled to the line!

After reading through this forum, I was suspecting the fan clutch, the water pump, or the thermostat. Both fans run fine at idle. The water pump has never been replaced (117,000 miles), and neither has the thermostat. I was thinking about running up to my neighborhood EZLube for the coolant flush, because they supposedly pressure-test and leak-check the entire system when they do that.

Sorry this was so long, but wanted to get ALL the info out there. I look forward to hearing your answers, and I thank you in advance for your help. Happy motoring,

Dozer

[abemcclellan]

i would check the thermostat, and the fan clutch first, then the water pump. then again you might have a clogged radiator filled with gunk.

[bryan1970]

to check the fan clutch just let it idle until it warms up or even begins to go to the red and if the fan is not raoring then you prolly need a new clutch. if you can stop the fan with your hand when it is getting to the hot range then you defiantly need a fan clutch. to check the water pump fo flow take off the radiator cap and start the engine. then rev the engine up to about 2000 rpm or highere and coolant should be shooting into the expansion tank from the top of the hole where the cap screws on. there isn't really a good way to check the T-stat. but i would bet that is is the water pump if it has never been changed before. if you do change the water pump put a new t-stat in at the same time it could save you trouble down the road and your already taking things off in that area so it won't be much trouble.

oh one other thing. it could be an air pocket in the cooling system. how did you bleed the system when you flushed the rad? the way to do it is fill it up with the bleeder screw/s out untill coolant comes out of them and no more bubbles. then put the screws back in and continue to fill it up until no more bubbles come out of the expansion tank. then start and run the engine between 2000 and 3500rpm with the heater on. and run it untill all the bubbles come out. it can take a while. but once you get all the air out of the system you should be able to add more coolant to it.

[kyle_baker]

hope for you it is only the fan clutch, a guy i know had a similar problem, but had to do alot of work and repairs. If it doesn't have too many miles on it and has been driven well then it shouldn't be too bad to have it fixed.

[e36_m3_Turbo]

i dont believe there is a engine coolant drain plug. thats why you need to flush it. put a hose in your extra coolant res and then open the drain in the rad. let the car run lik that until its clear.

[bryan1970]

ther is a block coolant drain plug. i think on that year it is on the pass side of the engine and behine the engine mount near the back of the block. some of the newer ones are infront of the engine mount on the pass side. i think if it is a regular bolt head on there it is a 16mm but some have an allen head on the drain plug. i think if it is an allen head the size is like a 6mm, although i might be wrong on the size of the allen head bolt it has been a while since i have done one of those. but the drain plug is on the pass side of the engine no matter what.