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coolant level raising when revved
Autosri - 17/3/12 at 12:43 AM

got a bit of a problem with my pinto and am hoping someone can help

the coolant is filled to the max marker on the header tank so start the engine the level raises slightly but only a couple of mm if you raise the revs to a fast idle say 1200 rpm the level rises again but about 3000rpm the level overflows with the cap off and is filled to the top with no air in the tank with the lid on

there is also a stream of bubbles comming from the lowest pipe in the header tank

anyone got any ideas what would cause this to happen

thanks

wylliezx9r - 17/3/12 at 06:05 AM

First question is why are you revving the engine with the cap off ?
If there is gas getting into the coolant system sounds like head gasket failure.
Is the system free of airlocks ? May just need a good bleeding.
HTH Dan

[Edited on 17/3/12 by wylliezx9r]

britishtrident - 17/3/12 at 06:27 AM

Nothing to worry about absolutely normal.

snapper - 17/3/12 at 07:13 AM

As the pump goes faster more volume is moved, with the cap off the water finds the easiest way out.
The thermostat is probably not open at this stage.
A radiator will be more restrictive to flow than an open 2" hole.

Dusty - 17/3/12 at 09:58 AM

I too have noticed some water level change as revs rise but half an inch. More important is where is the 'air' coming from. Options I can think of at this time of day are 1, an air lock in the system, 2, boiling out of fresh water you keep adding, 3, sucked in at a poorly fitting joint 4, leaking head gasket. The first two should be finite small amounts and the bubbles should stop eventually if you keep the header topped up. Top up from a boiled kettle to eliminate dissolved air? Sucking water in at a hose join is pretty theoretical and would be accompanied by water leaks at other times I would have thought. You can get a kit to test for exhaust gas in the rad/header. Blue dye that goes orange as gas from header is bubbled through it.

Autosri - 17/3/12 at 10:01 AM

Well after it was running with the cap on I noticed it was full to the neck so removed the cap to see if it did the same and it did

My first thought was head gasket from the bubbles I have a compression tester at home so will see if they are all cylinders are ballanced

Just noticed after the car running for a bit I have a small amount of steam coming from around the front so may have a small leak and if it's on the pump it may be pulling air in causing bubbles maybe

adithorp - 17/3/12 at 12:01 PM

quote:
Originally posted by Autosri
Well after it was running with the cap on I noticed it was full to the neck so removed the cap to see if it did the same and it did

My first thought was head gasket from the bubbles I have a compression tester at home so will see if they are all cylinders are ballanced

Just noticed after the car running for a bit I have a small amount of steam coming from around the front so may have a small leak and if it's on the pump it may be pulling air in causing bubbles maybe


That sounds like your cap isn't holding pressure (should hold about 1bar). Was there any pressure release when you undid the cap? The bubbles could be either cavitation in the pump or localised hot spots within the system boiling due to lack of pressure.