Bizarre Airlock!

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CitroJim
A very naughty boy
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Joined: 30 Apr 2005, 23:33
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Bizarre Airlock!

Unread post by CitroJim »

Out in the Activa this evening, doing the Dads Taxi round, I noticed a strange thing. The coolant temperature was reading a good notch lower than normal but the oil temperature was elevated to well over 100 degrees from its normal 80 degrees (the notch between 50 and 100). I had never seen the oil temperature this hot nor the coolant so low despite town driving.

At the earliest opportuninty I had a check and found the pipe from the top hose to the oil cooler just about tepid :shock: whilst the top hose was its normal very hot.

I gingerly released the pressure cap and ater a restart, water was found circulating normally through the oil cooler and both temperatures restored to normal.

I suspect the pressure cap. It was a "pattern" metal one and I've never been happy with it as often it created a vacuum in the cooling system when stone-cold. Luckily I got a genuine cap from a scrapper last week and have now put that on. All seems OK.

Anyone else ever seen an airlock occur in an oil cooler several months after a coolant change and really good bleed? Is the pressure cap a prime suspect? It never looses any coolant and I've never needed to top up.

One thing that came out of this incident was the realisation of just how much heat the oil cooler dumps into the cooling system when it is working normally.
Jim

A bit of a Citroen AX fan...
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jeremy
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Joined: 20 Oct 2002, 16:00
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Unread post by jeremy »

For an airlock to form there must be air (or another gas) - so where can it have come from?

I suppose if the filler cap didn't release a vacuum on cooling air could be drawn through a slack hose joint - or the water pump seal which is probably a lip type which will only seal with pressure behind it and not in front as it were.

Reminds me of the problems experienced by Cosworth in the 70's with the dry sumped DFV engine - the dry sump pumps were so powerful the oil seals were sucked in and leaked - remedy - turn them round.
jeremy
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weety
Posts: 532
Joined: 24 Oct 2004, 13:49

Unread post by weety »

i blame whatever bright spark decided to put the header tank lower than some of the coolant pipes :( ........i presume he then went on to position the heater matrix in the middle of the dashboard :shock:

oh and then he decided the best place for the bitron was underneath a headlight
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ACTIVE8
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Joined: 16 Nov 2004, 16:49
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Unread post by ACTIVE8 »

weety wrote:i blame whatever bright spark decided to put the header tank lower than some of the coolant pipes :( ........i presume he then went on to position the heater matrix in the middle of the dashboard :shock:

oh and then he decided the best place for the bitron was underneath a headlight
Yes, and that plonker also probably received a pat on the back from his bosses, a bonus, and a promotion for his crap ideas.
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