hodge Posted July 1, 2011 Share Posted July 1, 2011 What could cause a coolant system pressurization apart from head gasket falier. What's your views on this. Would it be possible that this happens if there was a small air leak or something else. Thanks John Quote Link to comment Share on other sites More sharing options...
Dnk Posted July 1, 2011 Share Posted July 1, 2011 Cracked head or block ? Porous head ? Seized shut rad cap ? Quote Link to comment Share on other sites More sharing options...
bignum Posted July 1, 2011 Share Posted July 1, 2011 Air lock. Quote Link to comment Share on other sites More sharing options...
Guest ugp Posted July 2, 2011 Share Posted July 2, 2011 Well the rad cap is essentially a pressure relief valve, by pressurizing the system to what ever is stated on the cap (mine is 1.3 bar), you'll raise the boiling point by about 25 degrees c. Do you mean there's too much pressure in the system? Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted July 2, 2011 Share Posted July 2, 2011 Seized thermostat? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 2, 2011 Share Posted July 2, 2011 Combustion gasses entering the coolant. Usually head gasket issues, but other possibilities are a cracked head, or a cracked block, or very very rarely a cracked turbine housing on a water cooled turbo. Obviously very high coolant temps will cause expansion and pressurisation up to the blow off pressure of the rad cap. Temp related issues should be obvious by abnormally fast rises in coolant temp. You should be able to isolate which cylinder the head gasket has blown on quite easily, a worthwhile check if the blow is tiny and might be hard to spot by just looking at the gasket after disassembly, or it will help when looking for a crack. A cracked or warped MKIV head is a scrap head though. An old map sensor and 5 volt power supply, connected to a scope can be used to see pulsation pressures in the coolant with a bit of fiddling, if you like gadgets. Removing a plug one cylinder at a time until the pressurisation ceases is quick and easy, sometimes just pulling a coil pack connector to stop combustion pressures in one cylinder is enough to see where a gasket has blown, or where a crack is. Have fun Quote Link to comment Share on other sites More sharing options...
hodge Posted July 2, 2011 Author Share Posted July 2, 2011 Am I correct in thinking the top and bottom rad pipe shouldn't go hard enough not to be able to squeeze easily. The coolant temps do not rise up and down the needle sits just below the half mark on the dash board gauge. Although I have noticed when the electric fans start they stay on all the time. With my car once the car temp has cooled down they turn off. So the fans can not cool it to the desired temp. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 2, 2011 Share Posted July 2, 2011 The hoses should pressuise enough to be hard to near impossible to squeeze flat. The system should see 1 bar without the cap opening, which is quite a bit of pressure. It's not got that Toyota red coolant in it, has it? If it contaminates some combustion gas colour change liquids it changes their colour by itself. You may be worrying needlessly? Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 2, 2011 Share Posted July 2, 2011 If it contaminates some combustion gas colour change liquids it changes their colour by itself. Is it me or have you been on the cider already this weekend Quote Link to comment Share on other sites More sharing options...
Westy Posted July 2, 2011 Share Posted July 2, 2011 is it me or have you been on the cider already this weekend Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 2, 2011 Share Posted July 2, 2011 I can understand your concern, but I haven't touched a drop today. It may be the effects of an excess last night though.... I'll reattempt it: It's not got that red Toyota coolant in it, has it? The chemical that cause the colour change when the coolant becomes acidic can cause a combustion gasses in the coolant test to give false positives. The chemical itself can cause an indication that gasses are present when they are not, if it gets drawn into the tester syringe with the test fluid. Now, talking of drink, what time is it? Oooh, three minutes to opening time :) Quote Link to comment Share on other sites More sharing options...
Lee P Posted July 2, 2011 Share Posted July 2, 2011 The stock water temp gauge won't tell you much, you need an proper gauge on there to see what's going on. Plug in to the syvecs and you can monitor coolant temps on there. Quote Link to comment Share on other sites More sharing options...
Bailey. Posted July 2, 2011 Share Posted July 2, 2011 Is this on yours hodge? Quote Link to comment Share on other sites More sharing options...
Guest ugp Posted July 2, 2011 Share Posted July 2, 2011 Am I correct in thinking the top and bottom rad pipe shouldn't go hard enough not to be able to squeeze easily. The coolant temps do not rise up and down the needle sits just below the half mark on the dash board gauge. Although I have noticed when the electric fans start they stay on all the time. With my car once the car temp has cooled down they turn off. So the fans can not cool it to the desired temp. Thats normal, you shouldn't be able to squeeze them flat. Quote Link to comment Share on other sites More sharing options...
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