[Jason R]

This is my fiance's car. Its got about 104k miles on it and it just started doing this last night. An alarm came on on the navigation screen telling her to pullover as the car was beginning to overheat. I popped the hood and the coolant reservoir was wet and could see where it had made its way to the ground in the same area underneath the coolant tank. We got the car home and I started it up, turned the heat on full blast and it was warm for about 5 seconds and then it immediately went cool.

Could the water pump be the culprit? or maybe the thermostat? Thanks in advanced!

[F32Fleet]

With that many miles I'm thinking a leak in the coolant system and probably the radiator. Only way to tell is pressure test.

[Jason R]

I checked all the hoses and radiator. Everything looked fine to me. And the only time it leaked was when it got too hot. Are the coolant reservoir caps on these cars vented?

[AlanAZ]

Are the coolant reservoir caps on these cars vented?

Yes. That's why the coolant tank was wet. It's probably now low on coolant. As an emergency measure, you can add distilled water to limp it to a repair shop, that's better than running it dry (unless you have some BMW coolant to mix 50/50 - best not to use can other type of coolant.)

Is it throwing any codes? Both the pump and thermostat are electronic, and can report failures. There have been posts on that here, you might want to search for them.

Has the coolant been replaced? It was due at 100K (or before.)

[burberry]

Originally Posted by Socom

With that many miles I'm thinking a leak in the coolant system and probably the radiator. Only way to tell is pressure test.

exactly what happened to my previous car.

[Jason R]

The only alarm we got was engine temp high and engine overheated. No alarms for anything else.

[F32Fleet]

Originally Posted by Jason R

The only alarm we got was engine temp high and engine overheated. No alarms for anything else.

You can have a slow leak which won't throw a code until it gets really low. My E90 330 had a leaking radiator for 2 yrs and I didn't know it until they pulled the head for a valve ticking problem.

[AlanAZ]

http://www.e90post.com/forums/showth...highlight=pump

From this thread - sorry, not good news, your symptoms seem to match exactly:

txusa03: I replaced the pump, thermostat, and the 3 Aluminium bolts that secure the pump to the engine block, plus coolant naturally. The new thermostat is made of plastic rather than Aluminium - so I guess that is the mysterious 3rd part you mention.

tuned2ride: Symptom was amber overheating warning, closely followed by red overheating alarm. I quickly pulled over and stopped engine. Upon checking under bonnet, radiator + hoses were cold, but small amount of coolant had vented.

I checked interior heating, and that was cold too. Luckily I was only a mile or so from home so waited for about 10 mins with engine off and drove gently for a minute then stopped for 5 - etc till I got home. I wouldn't necessarily recommend doing this - especially in warmer weather / climate. But in my case I luckily never got another warning on my limp home, and no more coolant was vented.

If a significant amount of coolant was allowed to be vented then one could risk causing engine damage.

--------------------------------------

I got the red overheating alarm a couple of days and took it to the dealership. They said that I had to replace: Water pump + thermostat + VANOS solenoid.

Currently have ~130,000 miles on the car, so I was out of warranty.

[aesfah]

Originally Posted by AlanAZ

I got the red overheating alarm a couple of days and took it to the dealership. They said that I had to replace: Water pump + thermostat + VANOS solenoid.

Currently have ~130,000 miles on the car, so I was out of warranty.

How much did all of that cost at the dealer?

[AlanAZ]

How much did all of that cost at the dealer?

Not me. It's from the thread I posted.

[Jason R]

i just checked the car this am. I filled the reservoir tank the other night to limp it home about 1.5 miles. i checked it this morning and it was completely empty. So I'm sure its leaking from somewhere. gonna try to find out today.

[ENINTY]

The coolant tank holds quite a bit of fluid. If it leaked out that fast (overnight) it should be pretty easy to spot.

[StoneCold]

Originally Posted by Jason R

This is my fiance's car. Its got about 104k miles on it and it just started doing this last night. An alarm came on on the navigation screen telling her to pullover as the car was beginning to overheat. I popped the hood and the coolant reservoir was wet and could see where it had made its way to the ground in the same area underneath the coolant tank. We got the car home and I started it up, turned the heat on full blast and it was warm for about 5 seconds and then it immediately went cool.

Could the water pump be the culprit? or maybe the thermostat? Thanks in advanced!

It sounds like my previous vehicle. It turned out that the water pump failed and the ground connection of the water pump needs to tight down properly. It was still under warranty at the time and the dealer replaced the water pump. I traded it in two years now. GL.

[AlanAZ]

I filled the reservoir tank the other night to limp it home about 1.5 miles. i checked it this morning and it was completely empty. So I'm sure its leaking from somewhere. gonna try to find out today.

Not necessarily. Unless you bleed the air from the system when you filled it (you wrote that the heater went cold earlier, so at least there was air in the heater core), it would have gone down during that drive.

[Jason R]

ok we did a pressure test on it today and it held pressure fine. my fiance's uncle is a mechanic and he came by and we pretty much ruled out the water pump & the thermostat. Looks like I'm gonna trailer the car to my uncle's house, flush the cooling system and refill. Now I would like to get this done tomorrow and need to know what coolant would be best to use since I obviously cannot get any from the dealership tomorrow.

So, what coolant can I use in this thing?

[GMWNashville]

OEM-anything else can cause damage to the electric water pump..and mixing coolant is a no no...

[NaTuReB0Y]

i had the same situation.....exactly how you explained.............

i replaced the thermostat and water pump.......problem went away.....

[Jason R]

Originally Posted by NaTuReB0Y

i had the same situation.....exactly how you explained.............

i replaced the thermostat and water pump.......problem went away.....

Did your car ever throw a check engine light for either one? did you do it yourself or take it somewhere? how much did it cost you?


i had the car up in the air and did a pressure test. no leaks. cooling system is holding pressure fine. i let the car run for a little while with the pressure tester on there and it never got to the point where it was too hot. Could it be the coolant reservoir cap? But where on earth would the coolant be disappearing and why? I guess I'll try the coolant reservoir cap first.

[F32Fleet]

Originally Posted by Jason R

ok we did a pressure test on it today and it held pressure fine. my fiance's uncle is a mechanic and he came by and we pretty much ruled out the water pump & the thermostat. Looks like I'm gonna trailer the car to my uncle's house, flush the cooling system and refill. Now I would like to get this done tomorrow and need to know what coolant would be best to use since I obviously cannot get any from the dealership tomorrow.

So, what coolant can I use in this thing?

BMW OEM + Distilled Water. It's not expensive stuff.

[Jason R]

Originally Posted by Socom

BMW OEM + Distilled Water. It's not expensive stuff.

I read on this forum that it was ok to use zerex g-05 coolant. Is that info wrong?

[Jason R]

Originally Posted by Socom

BMW OEM + Distilled Water. It's not expensive stuff.

I just called my local dealership and they told me its $30/gallon. I don't know about anybody else but i'd say that's some expensive coolant.

[F32Fleet]

Originally Posted by Jason R

I just called my local dealership and they told me its $30/gallon. I don't know about anybody else but i'd say that's some expensive coolant.

They're either lying of upcharging you like crazy. It's ~$20/gal.

http://www.ecstuning.com/BMW-E90-335...olant/ES10319/

http://www.bavauto.com/shop.asp

Try Indy Shops or different dealership. http://www.BIMRS.org