Water Pump Failure

[t_marat]

I think I have the famous water pump failure.
I can drive the car gently, it will not overheat. But If I press a little harder on the gas, the temp gauge starts crawling towards the red zone. I don't even need to be driving, just revving up the engine in idle is enough, temp starts rising quickly. The cooling hoses that go to and from the thremostat, they seemed like empty. I couldn't feel any fluid in them.
So is it correct to say the water pump is about to die completely? Is it safe to drive around gently till I get the pump with metal impellers? My work is only 5-6 minutes of driving from my home.

I don't know if the previous owner replaced the water pump, probably not.

[ironie]

Yes it probably is, provided your resivor is properly full, though it could be a failed thermostat, keeping higher revs in lowers gears, (like in second at 30 miles a hour, maybe 3k-3.5k or so) should cool it down if the thermostat is opening properly. Remember, overheating kills heads.

[t_marat]

The reservoir is full.
I didn't try rasing the rpm intentionally when the temp started rising. Its just too scary, the temp rises very quickly. And it starts rising the moment I rev up the engine.

[winfred]

not safe to drive, if it is a failed plastic impeller or a bad thermostat things can go bad quickly and change a $100 repair to a $1000

[ironie]

Winfred makes a good point actually. Thatr plastic impeller is specific to BMW.
I have never seen another car with it. Traditional water pump failures are usally pretty obvious due to the fact that they leak from the shaft. My M50 has almost 170k on it and had had the water pump done at least once, and when it failed it failed in the traditional manner, I had no fear of increasing the revs as opposed to sitting in traffic on a hot day idleing, Heat builds up quicker and is disipates more slowly at low revs. Reving the engine up forces the water through the system faster (if you have a impellor left)
The plastic impellor really is one of BMW dumber ideas. I assume they figured this out as well and gave it up in later models

[632 Regal]

could be a water pocket, try bleeding it correctly?

[t_marat]

I have driven the car in traffic jams at about 45C (100F) hot weather, and didn't have any overheating problems. I don't think it is something related to air trapped in the system. I just press the throttle a little harder and the temp gauge goes towards the red zone.

[t_marat]

Which one would you recommend?
http://www.bmaparts.com/epcvsoapimc.epc?cookieID=2410UZYV62410V0FEM&drillid=8&subcatid=800996@@Water+Cooling&clientid=bmaparts

[winfred]

hepu and graf have been good to me

[Bill R.]

Not quite, a number of car companies now use a water pump with a plastic or composite impeller, mercedes, vw, bmw and a number of others now are starting to use more and more plastics. They don't seem to have the problems that they did in the past.



Winfred makes a good point actually. Thatr plastic impeller is specific to BMW.
I have never seen another car with it. Traditional water pump failures are usally pretty obvious due to the fact that they leak from the shaft. My M50 has almost 170k on it and had had the water pump done at least once, and when it failed it failed in the traditional manner, I had no fear of increasing the revs as opposed to sitting in traffic on a hot day idleing, Heat builds up quicker and is disipates more slowly at low revs. Reving the engine up forces the water through the system faster (if you have a impellor left)
The plastic impellor really is one of BMW dumber ideas. I assume they figured this out as well and gave it up in later models

[Bill R.]

Same here, i've also had pretty good results with gmb on most cars.





hepu and graf have been good to me

[winfred]

laso's gone plastic, not sure if that's a good or bad thing, i am still wary of geba because i've had so many go bad on different motors, i get gmb for volvos but my main supplier world pac doesn't show them for bimmers so ....


Same here, i've also had pretty good results with gmb on most cars.

[t_marat]

Haven't ordered anything yet. After some though I am not really sure if it is the water pump. It is a mechanical thing, if it fails it should not work, right? What I had been thinking is that the plastic impeller could be slipping on the metal shaft, but doesn't sound really believable.
today drove the car for half an hour, keeping the revs not higher than 2500rpm. didn't overheat. after parking tried pressing the gas fast and hard. at first no overheating, but then temp gauge started moving towards the red zone. shut off, checked the thermostat hoses. the left one was very hot and stiff, the right one was not that hot but it was empty. I could squeeze it and hear coolant gargling in the radiator. Could a thermostat exhibit periodic failure? as far as I know it is a metal that expands at certain temperature. I would expect it to either work or not, ie closed or open.

[pingu]

Thermostats are filled with wax, not metal, that expands to actuate the thermostat. I guess that if some of the wax leaks out then the thermostat could behave oddly but I wouldn't have thought that it would misbehave periodically.

[Dr. evil]

If i were you i would make sure that the system is super bleed(zero air in the cooling system).
When it comes down to m50 termostats i was under the imperssion that when they fail the engine will run cold on the highway. at least thats what happend to me.

[bsell]

You are scaring the crap out of me...:(

I feel you are over-relying on your temperature gauge. It only reads the temperature of the water running over the sending unit. So if you have no water running over the sending unit, the temp gauge will read cooler than the actual temp of the engine. I am afraid you may have already cooked your head by driving with a compromised cooling system.

Let me put this another way. Back in the day I had a 944 come in on a tow truck after it quit running going up a mountain. The story goes; 'temp gauge went almost into the red, then flickered down into the normal range so I kept on driving without checking into this movement'. What happened is the engine puked the coolant out due to a leak, creating a rise in engine temp. As the coolant ran out, the water splashed onto the sending unit instead of continuously covering it, causing the gauge to flick up into the hottish range but not enough coolant hit the sending unit to send the temp gauge into the 'red' area. The end result of all this coolant loss was a banana for a head with every plastic vacuum hose melted onto the engine due to the severe overheating.

Folks have given stout advice to not drive the car until you have solid coolant flow through the radiator, confirmed by hot water in both radiator hoses without overpressuring (tight hoses) and no 'gurgurling in the radiator.' That gurgurling is your coolant boiling!:(

The easiest way I found to bleed a stubborn coolant system is to fill the radiator, use a coolant system pressure checker to pressurize the system, then open the bleed screws to burp out the air pockets under pressure.

I don't know that the symptoms you describe are from just an air pocket. You might have a bad water pump or possibly engine compression leaking into the cooling system causing repeated air pockets. Either way, I would not drive the car without finding out why your engine temps and cooling system are acting funny.

Brian

[t_marat]

well, I hope and do believe it is not so bad. till this time I never ever had any problems with the cooling system. as I wrote above driving in heavy traffic at a very hot day, and never overheated. My coolant levels are normal, they have stayed at that level for almost a year.

The gurgling I mentioned is not due to the boiling coolant. Coolant never boiled. I could hear it only if I squeezed the right hose coming out of the thermostat, which was empty inside (the left hose was stiff). otherwise there is no gurgling.

[Dr. evil]

the hose should not be empty.

make sure you bleed the system

[t_marat]

Picture speaks for itself. and it actually explains why at lower revs engine did not overheat. The part of the plastic vane that was still on the shaft "catched" the broken one and made it turn around, pumping coolant. At higher revs this connection broke down.
I have looked all over but couldn't fine a water pump with metallic vanes, so installed plastic one. I need the car, so couldn't wait 2 weeks till I get a new one from bmaparts. what do you think, should I change it again for the one with metallic vanes or not?

[pingu]

How long did the old pump last? I'd leave the new plastic one in there - it'll probably be good for another 100,000 miles or so...

[Evan]

leave it in... you're good to go for another 60K miles

I just put a water pump in mine... bought it from BMA (plastic impeller)