Thermostat replacement- time for new waterpump? - BMW Forum

maxslomoff · 12-03-2008, 06:36 PM

hey everyone,
i just drove from san francisco to LA and luckily i had some bad luck right when i got down here. The car started over heating. There was no hot air coming out of the heater (which has been happening on and off for the last few thousand miles) and i heard this is probably a sign of a bad thermostat that gets stuck in the wrong position. I think i learned that the Tstat has to be replaced every so often so, i'm guessing thats my problem. I did recently purge and refill my radiator but i'm pretty sure i did it the right way (i ran the engine and released all the air pockets through the little pressure valve). i've read that either a clogged radiator or a bad water pump could also be the problem.

after i let the car cool down for a while i got back on the freeway, it started to heat up and the temp gauge was at the red for a few moments, but then the needle came back down to the middle. i'm assuming this is a sign that the thermostat was knocked back into place...

so thats my story and MY QUESTION is >>> do water pumps go bad? is this something that i should replace along with the tstat? or is the waterpump a pretty long lasting piece? My car has 160k miles on it. a 325is. thanks a lot for reading and for any advice you can give me

max

kandi08 · 12-04-2008, 07:59 AM

Hi mate.
I have just had the same problem fixed.
Head gasket.
Ive got about the same amount of miles as you,
but have 318i on 97 plate.
I noticed a small amount of white stuff, about 6-8 inches up, from the bottom of the dipstick.
The water pump is positioned about 2cm away from the head gasket seal on my engine.
The water pump seal had broke, there fore allowing water to get to the head.
I luckily caught it in time, and i still had to have a head skim,(it was off by 4 degrees)
A new head kit, and fifteen hours of my engine slaves hard work.
Cost me nearly £650.
Apparentley my water pump has a ceramic float, which obviously if it gets to hot will crack.(not sure if yours is the same, but would guess it is)
The thermostats on E36, generally break at some point.
Causing erratic temperature readings.(they useually get stuck)
Another possibility is trapped air in the cooling system.
E36 are a little tricky to bleed.
Has to be done twice sometimes.
Therefore if it wasnt done properly previously .....
Hope i havent shit you up,
but also hope this information is useful.

maxslomoff · 12-04-2008, 09:34 AM

definitely is kandi08
thanks a lot

voodoo712 · 12-04-2008, 01:07 PM

shit the same thing just happened to me yesterday.
im thinking that the problem is that my car (e36 328i)
has had 12 years kept in the garage over the winter,
but i bought it this year so it is her first year outside.
so the Tstat blew! the needle was bounching on red and
the engine began to smoke. NOT good!

thanks for the advice.

maxslomoff · 12-04-2008, 10:22 PM

i found an answer at pelican parts

apparently the plastic water pump goes bad after many years typically so i'm not going to risk it. i'm just going to replace it while i have that part of the engine exposed for the tstat anyway.

actually, first i'm gonna take the radiator out and the fan off and see if i do infact have an old plastic water pump. i had some cooling system work done in '01 and maybe they installed a metal pump at the dealership then...

drz · 12-05-2008, 12:01 AM

Once you have it all apart, you may as well just service the cooling system altogether. Yes, it adds to the expense total, but I would consider not only changing the tstat and water pump, but also going to an aluminum t-stat housing, changing the hoses, the cooling fan clutch, and the water pump. If you don't know when the radiator and the overflow tank were replaced, do consider changing those too. It will be a pain to have to do this all over again in 9 months if you don't have to.

Also, use the BMW coolant. It was formulated especially to prevent electrolysis. Don't cheap out. Instead of getting it from the dealership, you can save some cash by buying from Pelican Parts or some other online store.

maxslomoff · 12-05-2008, 12:45 AM

oh thanks drz for the rec

i'm looking at my manual here and i can't tell where the cooling fan clutch is...

is the cooling fan the one thats in front of the radiator?

maxslomoff · 12-15-2008, 03:01 PM

?
do these symptoms make any sense:

so the other day i replaced the tstat, water pump and tstat housing, and the belts. the old parts appeared normal after i took them out. i cleaned all the connections on the head and reassembled everything.

i went on one small test drive and the car ran perfectly. the temperature needle was locked in the middle like normal and the car sounded great. about an hour later i took the car on another drive and noticed that the engine was heating up again. the needle would rise to the last notch before the red and then it would come back down again to one notch hotter than the middle. and it continued to fluctuate like this... the needle did not seem to return to the middle, if anything it stayed stagnant one notch right of the middle for a while.

what could be going on here?