My son's old Xsara doesn't circulate the water properly. The thermostat opens OK and we've flushed it through. The flushing water runs through the heater OK and out of the anti-airlock 'bicycle valve' on the exit pipe with gusto. The rad is ok.
It seems as though the impellor of the water pump isn't working. Can this happen?
I suspect there is a tiny head-gasket leak as it loses small amounts of water and it seems to be overly pressurised. Could such pressure overcome the pumping action of the impellor? We would be very grateful for any expert answers to these questions.
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Hi john,
May I relate a tale that might help you ?
I have worked on fixing cars/motorbikes all my adult life so I speak from a little experience.
I was trying to solve an overhating problem on a Vauhall viva; To cut a long story short the issue was resolved when I discoverd that the plastic impeller had a hairline split- the result was that the spindle was spinning, but the impeller was not.
I put in a new pump and the problem was resolved.
Just as a futher aside I believe some modern Skoda,s had this proble? Later models had a metal impeller fitted.
My conclusion is that modern designers do take any lessons from past design mistakes ?
Hope this of help to you ?
Regards Ivan
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Sounds feasable, the only reservation I have is that if the heater is working it would seem to indicate that the pump is. When you say that the radiator is alright, do you mean that its getting hot all the way down? Does it overheat all the time or only when its being worked hard?
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Many thanks, Ivan and Peter.
No, the heater doesn't work because virtually no hot water flows through it, although there is no obstruction when flushing it . That's what made me think the water pump impeller might no longer rotate with its pulley [Peugeot OHC engine, cambelt driven, I think.]
The radiator is OK, it doesn't leak and isn't blocked. It only gets hot at the top - further evidence that the water isn't circulating. Thermostat is OK, opens nicely in pan of hot water.
I don't want to attempt water pump inspection unless assured that Ivan's observation can apply to this water pump! So main question - can this water pump impeller become disconnected from pulley?
I still suspect tiny head gasket failure - there was a slight layer of mayonnaise under the cam cover [I took it off and retorqued the head to 65ftlb - roughly an extra 45degrees each bolt - having found a US post from a mechanic who reckoned he saved a few engines doiing that. It's made no difference!]. However, the oil is OK - no water in it. At 124k I suppose imminent head gasket failure is possible. Could pressure overcome a functioning impeller?
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Sorry, I misunderstood your post, it does sound like water pump failure, something I have never had in over 50 years of motoring, but I know it can happen. I can't think of any other logical reason, you have eliminated the thermostat and thats the only thing that can impede the flow, no heater and no radiator circulation certainly points to the pump.
The mayonaise may indicate water ingress if the car is regularly drive fairly hard and fast, if its only been poodling about that can form due to lack of heat. A leaking head gasket though will not normally cause a car to overheat, what can happen it that the combustion pressure blows most of the water out - that's waht causes the overheating.
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Thanks, Peter - looks as though we need to inspect the water pump. My Haynes Peugeot 309 manual says cambelt has to come off - would anyone know if just loosening the tensioner allows the water pump to be removed? Otherwise it's off to my trusty indy....
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Possibly but most of the work is in getting to it!
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I would recommend that you still replace the timing belt even if it is possible to remove the water pump by just removing the tension on it. In my experience these belts don't like being "disturbed" in any way especially if the have done a good few thousand miles and for the sake of about £15 for a new belt is it really worth the risk of having it break ?
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Just in case anyone's interested - my diagnosis was correct. It looks as though some sort of plastic compound has dissolved/disintegrated leaving five thin flat steel blades, to which it it was glued, spinning uselessly in the water. The absent plastic stuff should have done the actual impelling.
I have never seen this type of water pump impeller failure described anywhere but it must be pretty common as there are lots of these engines around in Peugeots.
I thought some of HJ's resident experts might have mentioned this - perhaps it needs publicising - or perhaps it really was a rare one-off.
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