Weird Alfa cooling issue

[wuvvum]

OK, the 156 is being a PITA again. It had been having cooling issues and the diagnosis was the coolant wasn't circulating properly, so I drained the system and flushed and backflushed the feck out of the radiator - it was a bit sludgy, but nothing too major. Put it all back together on Thursday and took it for a spin and it was fine - temp gauge at 80, heater lovely and warm, all coolant hoses at a similar temperature etc. etc. Took it out again last night, and it started getting hot again (it's never actully boiled up as I've never given it time); switched off and the bottom radiator hose is stone cold, which is exactly what it was doing before I flushed the system out.

 

So, given that it's almost certainly not a blockage in the system, and it ain't a thermostat problem as I've taken that out, what could be causing an intermittent coolant circulation problem? If it was doing it all the time I'd suspect the water pump had had it, but I can't see how a mechanical water pump could work some days and not others. Any ideas from anyone with better mechanicing skills than me?

[Espacetic]

I would re bleed the system, sounds like you have some air still trapped in it.

[meggersdog]

The Ford Probe V6 had a plastic impeller which would spin free of the input shaft.Sometimes it worked other times the shaft would spin but the impeller wouldn't so yes a mechanical pump can work sometimes and not others

[wuvvum]

The Ford Probe V6 had a plastic impeller which would spin free of the input shaft.Sometimes it worked other times the shaft would spin but the impeller wouldn't so yes a mechanical pump can work sometimes and not others

That sounds like a possibility. Just had a look on the Bay and replacement waterpumps for these are relatively cheap, but realistically I'd need to get the cambelt replaced at the same time, so the cost could mount rapidly. Arse...

[wuvvum]

I would re bleed the system, sounds like you have some air still trapped in it.

I've bled it as best I can - the expansion tank appears to be the highest point in the system so shouldn't be too many potential air traps. Might try it one more time though before forking out for water pump replacement...

[Espacetic]

Keep the cap off, bring the revs up and keep squeezing the bottom hose until the hose goes hot, then road test it keeping the revs up. Leave to go cold, then recheck the water level. Some cars can be a total shit to get the last bit out of.

[dieselnutjob]

Some cars can be a total shit to get the last bit out of.

Yep, like Peugeots and Citroens.

 

The XUD in my sisters 309 airlocked so badly that it blew the head gasket. They have 3 bleed screws on them that have to be opened up to get the air out. With some older froggy stuff you have to lift up the expansion bottle and tie it up to the open bonnet to get air out of the system. Sorry but I don't know anything about Italian shite

[dollywobbler]

The other trick I've used with XUDs is to raise the front of the car using ramps or a slope.

[myglaren]

A lot of folks with Citroens and Puegeots raise the coolant level by filling from an inverted 2L coke bottle with the bottom cut off, sealed with a bit of blue tack.

 

Never had to do that with any of mine though.

[Espacetic]

The other trick I've used with XUDs is to raise the front of the car using ramps or a slope.

 

Bit cruel to Chinese people..

[Bren]

Water pump impellers becoming detached is a big VW problem. It seems likely for the 156.

 

Incidentally, I never had any problems with my XUD xantia when replacing the coolant.

 

You can have a problem when the filling point (expansion bottle) is lower than the highest part of the water jacket / external cooling system.