P38, 2,5 TD, coolant / waterpump issue?

Gents.
Started loosing coolant two weeks ago. Have been looking all over for a leak, and the conclusion is that overpressure in the system forces the coolant out from the expansion tank. Did a major overhaul last summer, head, headgasket, new waterpump (metal impeller), thermostat, o-rings heater matrix.
No bubbling or pressure when standing still and letting the engine work up the temperature. Tried to change the viscous fan, new exp.tank cap. Still the same.
As there are no bubbling when I rev the engine when standing still I suspect that there are no or little circulation of the coolant in the system causing the coolant to boil when the engine is working a bit hard, and then pushing the coolant out from the expansion tank leak hose.
The question now before I pull the waterpump is: has anybody heard about a waterpump with metal impeller where the impeller has come loose? Could the impeller come loose when heated?

Thanks for any suggestions before I start with the head gasket.

Larsern

It's usually the plastic impeller type that people have problems with. Have you flushed the system out? Check if the baffle in the top of the rad is still in place. If you take the rad off to flush it, put a marble in one of the outlets and see if it roll out of the other. If it does then the baffle has broken off.

New rad one year ago, new coolant same time....no dirt in the coolant or exp.tank...

Did you change the viscous fan? You said you tried,have you tested it. get the engine hot and try to stop it with a rolled up newspaper,if you get confetti then it's ok.

try the hose disconnected method to see if it's pumping water around?

Newspaper test is done ok. Old fan not too good, new fan good.

Hose disconnect method, please guide me.

Is the engine actually overheating indicated on temp gauge. Or have you just got coolant loss?

Larsern said:

New rad one year ago, new coolant same time....no dirt in the coolant or exp.tank...

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Did the rad have the baffle though?

Sounds like an airlock somewhere. Is the little pipe from top of rad to expansion tank free?

I have had a couple of situations where the temp has gone all the way up and red light coming on. That was how I got aware of the problem. The Air-con fans working at full load. Normally the temp is rising to the normal level and stays there, then after some extra load on the engine, uphill, the temp went up-up.
Will try the marble test too.

Been very thorough with re-filling the coolant. airlocks almost out of the question. All has been working fine until it started to f***up two weeks ago, so something happened suddenly.

Overheating under load sounds like viscous fan.

Yes, but changed and tested.

Larsern said:

I have had a couple of situations where the temp has gone all the way up and red light coming on. That was how I got aware of the problem. The Air-con fans working at full load. Normally the temp is rising to the normal level and stays there, then after some extra load on the engine, uphill, the temp went up-up.
Will try the marble test too.

Been very thorough with re-filling the coolant. airlocks almost out of the question. All has been working fine until it started to f***up two weeks ago, so something happened suddenly.

Click to expand...

Do you know anyone with a static test rig? Sounds very similar to the problems you get when the C shaped hose at the back of the head is weeping. This causes an air lock and hot spot in the head circuit and eventually expulsion of coolant from the overflow due to pressure build up.

When you fitted the thermostat, did you put the bleed hole in the 12 o clock position?

Yes, bleed hole in 12 o'clock.
No, I don't know anybody with a static test rig.
Perhaps I should change the C shaped hose?

The engine has done 10' since overhaul without any issues at all. So something just happened.

I can also mention that since we have cold winters here I have installed (a few years back) an electric water heater with built in circulation pump inline with the heater matrix. when I refill coolant I run this heater and that forces any air lock out of the system. Almost like a pressure filler.
When running this I can always add a litre of coolant a few minutes after things normally has stabilized.

10'? So it made it to the end of the drive?

Total on the clock is 175 000 km, 10 000 km since overhaul

Just back from travelling. Cold here so today I took her for a spin. After some steep gradients she came with the red light and temp all the way to the top.
Managed to feel the temperature on the rad by my hand burning hot on the top while 10 cm down it was ice cold. The heating matrix inside the car is pouring out heat so my conclusion now is that the water pump is circulating the water, but probably the baffle in the rad is gone.
New rad is on its way.

Larsern said:

Just back from travelling. Cold here so today I took her for a spin. After some steep gradients she came with the red light and temp all the way to the top.
Managed to feel the temperature on the rad by my hand burning hot on the top while 10 cm down it was ice cold. The heating matrix inside the car is pouring out heat so my conclusion now is that the water pump is circulating the water, but probably the baffle in the rad is gone.
New rad is on its way.

Click to expand...

The baffle MUST be in place, as coolant comes in at the top and goes out at the top, the baffle is there to force coolant down the inlet side and up the outlet side. If it is not there coolant just flows across the top and is never cooled. Sounds like that is your problem. Do the marble test on the new rad before fitting.

In checking rad change thermostat,if heater is hot ,doint sound like head gasket ..If you put heater fans on full does it keep temp down ...... .

dubbleRR said:

In checking rad change thermostat,if heater is hot ,doint sound like head gasket ..If you put heater fans on full does it keep temp down ...... .

Click to expand...

From his post 17 it is obvious what his problem is.