How to identify either a Thermostat/Waterpump problem?

[Goon]

Hey guys,

I've got a possessed cooling system. I had some cooling issues a few days ago.

Let's entertain the thought that the system is bled properly. How would one identify if it is either a water pump or thermostat problem?

Symptoms:
- When the heater valve is open, there's no heat, which I assume means there's no coolant going through the system
- You can be travelling along a highway, the temp gauge will start rising, pull over, relieve some of the pressure, the coolant level drops, set off again and it goes back to normal.


Are there any other components of the cooling system other than the radiator, hoses, thermostat and waterpump?


Any help would be greatly appreciated. This is very frustrating for me.

[Ruger]

What i do to test water pump is open the radiator cap yank the throttle body and give it a decent rev and you should be able to see coolan spit through up near the cap.

Sounds to me like it needs a good bleed? how hot does it get? you mentioned in the wakefield thread that you bled it there? did you have the heater on when you did so?

[Goon]

Yup, the heater valve was open, revved the engine a couple of times until it was a stream of coolant, and no more bubbles and then tightened the bleed screw. It hasn't hit the red zone, every time it starts rising towards 3/4 I shut it off, cool it down.

[BM AUTOWERKS]

Sorry Goon BUT, if you have a blown head gasket it will cause a rise in pressure quite quickly, and possed cooling system problems.

That is the worse case though....

[Goon]

That's what I was scared of John! There does not appear to be any cross contamination of fluids. I'm going to try it without the thermostat and try bleeding the system again, see if it's maybe a faulty thermostat.

[silverbullet]

mayb drill some small holes in the out side of the thermostat. Also when u pull the thermostat out chuck it in a pot on the stove and see if it opens, easiest way to tell. And i have seen some brand new ones not work either so best check the new one before u put it in.

[niall]

here's a basic test which should give u an idea if its the water pump or headgasket issue, With the water level right up in the radiator take the revs up to about 3k, the water level should drop down quite a bit, this tells you the water pump is working well.

If the water rises or bubbles and does not drop down when the revs are increased this would indicate that there is a problem with the water pump

[Gringo_Starr]

If you're going to do the thermostat its not too much more effort to remove the water pump, then you can 100% rule it out. Not having any heat through the vents could also be blocked heater taps (common for them to gunk up with age) or the ihk may not be opening them (you can unplug the connector on the taps & they will default to open). If it is the head gasket I wouldn't expect oil/water mixing, but more coolant/combustion chamber leaking, so lots of pressure/air bubbles in the cooling system.

[niall]

lol, the last one of those water pumps i did, i broke it when i was removing it and the customer complained because he couldnt get 25 bucks from the reconditioning company

[xsile]

Hi there! Has the waterpump ever been changed? If not and the car has over 170K's on it i would be doing that first, My car did the same thing about 6 weeks back and found the impellor in half has i removed the water pump.

Also if the pump has not completely broken but just got a split in it its possible the impellor is free wheeling when the motor warms up and becomming insuffecient to cool at higher water temps.

[Goon]

Thanks for all the input guys! I ended up being so fusterated with the car and ended up taking it to the shop up the road to see if they could diagnose the problem, then I would decide how to proceed/fix it myself. The water pump was the culprit as it seems. It had a split plastic impeller. The mechanic mentioned that when it comes to the waterpump, it either works or it doesn't, but strangely it was intermittent with mine.

Elvis has been behaving himself the past few days since it got fixed so hopefully that's the end of my cooling woes. The only issue that remains is the viscous/clutch fan which really isn't operating as it should.

[BM AUTOWERKS]

Goon, if the radiator is not hot in the middle the viscous clutch will not engage, say there is and air pocket or faulty thermostat, the radiator will not get flow thus the fan will not engage, just a tip, if the rad is hot and the fan still doesn't engage then the fan clutch is faulty, it relies on hot air flow coming through the rad to function correclty.

[2blubmws]

i didnt realise the plastic impeller was a problem on the m40/42, i thought it was just the 6 cyl cars. goon is yours an m40.

also, i have had the fan clutch replaced on my e36 due to it overheating, but now i think its on all the time. its ment to only start up when car gets to operating temp right?

[Goon]

Mines an M43. Basically the M40 update.

A fan clutch's basic operation is supposed to operate in stationary traffic to suck air through the radiator when the car's not moving.

[2blubmws]

Yeah, but doesnt it use some sort of thing that only kicks in once the cars up to temp, or does it just kick in when the cars stationery?
when mine died it caused the car to overheat on slow crawls uphill in the heat. it wouldnt be necessary in -5 degrees in the snow, the cars getting cold air anyway without getting it forced in.