Water pump test

[Streethawk]

Does anyone know how to test a water pump in situ?

My 200T is suffering in the heat - have tested the thermostat, replaced the radiator (£20 from scrappie - old one was 2/3rds gone), the fan is going fine.

However, the temperature keeps rising then falling off, until after about the third cycle it justs rises until the system boils :|

advice, similar problems anyone?

 

[tom7035]

I don't think a pump actually stops pumping coolant so long as it's able to spin and not seized, but will start leaking first if it's on it's way out. Try a pressure check on the system, you may have a head gasket problem.
Did you back-flush the second-hand rad. before you fitted it? This might be worth a try. I'm also not an advocate of 'testing' a thermostat just by dunking in some boiling water to see if it opens - cheap item - renew it and try.
Cheers, Tom.

 

[turnipsock]

I also suspect that my pump is not working correctly.

I tried getting some speed up and then putting the car into neutral and free wheeled for a bit. In theory, the temp should drop as there is no load on the engine but it's getting loads of air flowing through the radiator. However my temp started to rise! The only thing that would cause this is if the coolant isn't flowing around the system.

 

[tom7035]

There's not really much to a pump Turnip/Streethawk. Just a bearing, seal and impeller, (impellor?) and it would only stop 'impelling' if (1) it wasnt turning or (2) the vanes on the impeller were corroded away to nothing and that's highly unlikely.
Any others care to comment?

 

[Streethawk]

so, the pump could be stuck/sticking occasionally

hmm, i always wonder what other people's idea of "cheap" is

well, i suppose the testing method on a thermostat could be seen as "dunking" - but scientifically carried out with a thermometer several times gives a pretty good indication (that's how i found one to be really quite sticky)

the flush would be a good idea - i'll sort it tonight as the weather seems to be holding

the other problem i'm having is that despite parking "uphill" and with both heating matrices open, the heating doesn't work every time...

 

[TimN]

The only test that you can do on a pump is to remove the fan belt and then grab hold of the fan and check for play in the bearings. However, this is not going to help you as the impellor and pully are directly connected by the shaft/boss and so if one is turning so is the other.

You have not stated the method of control of the fan. Older cars are directly linked and the fan works all the time even when the engine is cold so whilst a little inefficient the fans were never a problem, then viscous fan couplings were introduced followed by electro-magnetic clutches and then electric fans controlled by thermocouples. Any of these systems could fail.

I have to say that it does sound like a head gasket problem. First check the condition of your oil and water as a guide.

Other causes for over heating are binding brakes, or faulty wheel bearings, cv joints and incorrectly adjusted timing, if indeed that is possible on your vehicle.

 

[turnipsock]

I remember having to set up a pump on a Lotus engine, the impeller had to be set to a specific distance from the casing. To close and and it would risk rubbing against the casing, to far away and it wouldn't impell. (are you sure these are real words?)

The good thing with the seven was, that when took the radiator cap off you could see how much coolant was flowing round.

 

[996jimbo]

I also suspect that my pump is not working correctly.

I tried getting some speed up and then putting the car into neutral and free wheeled for a bit. In theory, the temp should drop as there is no load on the engine but it's getting loads of air flowing through the radiator. However my temp started to rise! The only thing that would cause this is if the coolant isn't flowing around the system.

Just a thought about your test - although there's load of air flowing when you're coasting the water pump (presumably being driven directly off the engine) is not pumping very fast as the engine's at tickover and may therefore lead to a build up of heat.

Just a thought.

 

[Streethawk]

The only test that you can do on a pump is to remove the fan belt and then grab hold of the fan and check for play in the bearings. However, this is not going to help you as the impellor and pully are directly connected by the shaft/boss and so if one is turning so is the other.

You have not stated the method of control of the fan. Older cars are directly linked and the fan works all the time even when the engine is cold so whilst a little inefficient the fans were never a problem, then viscous fan couplings were introduced followed by electro-magnetic clutches and then electric fans controlled by thermocouples. Any of these systems could fail.

I have to say that it does sound like a head gasket problem. First check the condition of your oil and water as a guide.

Other causes for over heating are binding brakes, or faulty wheel bearings, cv joints and incorrectly adjusted timing, if indeed that is possible on your vehicle.

it's a thermocoupled fan - coupling seems to be working fine, as there is a big fan howl when over 2,500rpm when engine is too hot.
brakes are fine, timing needs checking out, head gasket - no emulsion so probably ok.
could be cv joints, but dunno what to do about that. can only say that it seems to roll downhill without too much noise or any evidence of frictional slowing.

 

[tom7035]

My advice at this point - back flush the rad, fit a new thermostat, run the car & see what happens. With luck, all will then be fine.
Cheers, Tom.

 

[shrekky]

There is another thing that can happens to a water pump,is rare but have seen it happen more than once,is that the shaft driving the impeller has snapped inside the outer casing,which means it does turn,when it catches,but obvioulsy not at the correct rate, a pressure test is the best answer to do first,any reputible garage should be able to do this for you.

 

[turnipsock]

Just a thought about your test - although there's load of air flowing when you're coasting the water pump (presumably being driven directly off the engine) is not pumping very fast as the engine's at tickover and may therefore lead to a build up of heat.

Just a thought.

I know what you mean, but I thought there should be enough of a flow to cool the engine rather than heat up. the way it happens is like there is nothing flowing around at low revs and there is some flow at high speed.

By the way there is another thread kicking about about my cooling probs. 320CE getting hot.

I have already given the radiator a reverse flush, by the way.

 

[Streethawk]

reputable garage?!?!

thanks, i needed a laugh!

 

[MW]

Pumps are very simple. A shaft, and impellor, and that's it. If you drain down, and discontect the rubber pipes, you can look into the pump and see if things are turning. If they are, all is OK. Only the seals will go. At the back of 124 pumps is a small 'relief' pipe that drains water that is passing a weak seal onto the undertray. This is to protect the bearings. I think a pump unlikely as it would have to have cracked the shaft so it will not turn. Very unlikely. Can't think why anyone would replace a pump unless the seals had gone as these are synthetic rubber. Bearings will go, and it will be noisy, but it will still rotate, and pump.
I once had a second hand radiator that looked good, but was corroded inside.
I would try new thermostat (cheap) and while out try a full corrosion cleaner. Then a big flush through. Install therostat, and hope.
It sounds like a head gasket. But as the above is cheap, it might be worth a first port of call.

 

[mercman_1]

Overheating

One other possibility is the pressure cap on the reservoir, failure to hold the pressure allows the water to boil inside the engine block which causes air/steam lock and halts coolant circulation.

 

[MW]

The pressure cap is a good idea, and one to check. I had one go on a SAAB once. It looked fine, but antifreeze was boiling over and down the radiator header tank, leaving blue tell tail signs. A new one fixed it.
The advantage of replacing it is cost. Might be £5?

 

[Streethawk]

Well I'm certainly not ruling out an air lock, but i've tried many things to clear one...

as for the rest - no joy really (but haven't tried corrosive flush)

 

[Streethawk]

right - i think i've found it at last

had the pump off and the impellor has a crack in it (the "head" piece itself is made of plastic) - so it turns, but not when there is a slightest bit of resistance.

my theory is that it is moving a little water, but nowhere near enough to cool the engine

what are the chances of getting just the impellor as a spare part?!

 

[turnipsock]

See!

I better check out my pump.

I think you will be able to get the individual parts from a dealer.

 

[spannerman]

Guys ,
Let's face it if the pulley is rotating then the impeller is impelling (this thread could get very technical yet), and the coolant is going round and round.
Methinks it's not that.

I've seen water pumps with the bearing growling and a constant drip because the seal is gone as a result of the shot bearing, and the sytem would not be overheating unless you let it drip for a week and the level went low.

My moneys on either a partially blocked radiator, and/or a slightly duff thermostat.