Faulty expansion tank cap?

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Chris Peddie
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Faulty expansion tank cap?

Post by Chris Peddie » 31 Jul 2002, 01:57

Hello all,
As part of my ongoing quest to discover the cause of my 1.9td running temp varying so much (usually between 80 and 90 though so not too high) I was trying to confirm no air locks were in the system this evening using my leaky header tank method (must get more blue-tack next time!) I noticed two things:
1 - I could make some bubbles come up through the header tank by blipping the throttle, but at constant revs and idle there were none. Not really worried about this as the car doesn't use any coolant.
2 - when I had put the expansion tank cap back on and it was cooling down, I could hear air being sucked past the cap seal - noise stopped when I took the cap off again. Should it be able to do this?
So, 2 questions really: should I really be concerned at the temp varying this much (i.e. between half and three quarters on the gauge) or am I worrying about a problem that isn't really there, and should I try replacing the expansion tank cap? Top hose is definately firm when hot so system is pressurised.
Cheers in advance,
Chris
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Dave Burns
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Post by Dave Burns » 31 Jul 2002, 04:56

I think you have answered your own question when you said "the car doesn't use any coolant" which it certainly would with a leaky cap, without the pressure generated with a good cap, the water evaporates at to low a temperature and get's out, sooner or later you end up with a low coolant level.
Dave
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Chris Peddie
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Joined: 29 Apr 2001, 17:04
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Post by Chris Peddie » 31 Jul 2002, 13:43

Thanks for the response Dave, I had a feeling I might be worrying over nothing!! Have also come up with a theory for the temp changes coming down to the location of the sensor and ambient temperature, although the rad isn't as effective as it used to be. Ho-hum. :-)
Cheers
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B_Draper
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Joined: 16 Feb 2001, 18:51
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Post by B_Draper » 31 Jul 2002, 23:11

Hey Chris
I wouldn't worry too much about this. I get this temp range on my '94 ZX 1.9TD. It maxes at 90 when I'm pushing the car hard or 80 - 82 when I'm pootling along without any turbo boost. Very little coolant dissappears from the system so I dont't get concerned as long as the temp guage drops back to 80 - 82 when on the move !
Hope this is of reassurance!
Ben
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