Hi Guys, currently tracking down an overheating problem for my 91 TT.
Things I’ve done so far:
fixed all external leaks
replaced filler cap, thermostat, water pump, and crossover pipe
flushed the coolant system, several times
compression test (no results here indicate a head gasket problem, all cylinders in the range of 135-145 PSI)
Despite this, the symptoms are:
Car overheats quickly once at temp (20-30 mins if driving spiritedly)
it is losing coolant, as once cooled down, filling up is required, and it can take several litres if overheated
on startup, lots of bubbling/ frothing in the filler neck
I will probably be taking the engine out completely to refresh at some point, but does anyone have suggestions of checks/ tests to do with the engine still in the car?
I hate to say it luke but it sounds like a head gasket issue to me unless you can actually see where there is water coming out.
I have seen this problem twice before.
If you think about it, if you can’t see water coming out but you are losing water, it must be coming out of the exhaust in the form of steam.
Do the blue liquid head gasket test, as a compression test through the spark plug holes is not a 100% head gasket leak test. If there are no visible leaks and the hose pipes are hard or very hard, it will still be pressurising within. This could well be a head gasket or gaskets going or gone. Buy the test kit for a few quid, they are pretty accurate. Also, it might be rare for these cars but check your heater matrix hoses, see if they are hot when heating is on, or one hot one, warm or cooler might indicate reduced circulation in the heater core. I am thinking head gasket though.
When i had my block and heads boiled and milled last year before rebuild of engine the water jackets on both block and heads still had quite the corrosion visually. This being said i wasnt satisfied so i bought 2-32 oz bottles of evapu-rust and for my first week after initial starting I ran the bottles of rust inhibitors plus water with old thermostat, as stated above 1 week idling and some hard pulls to seat rings and set my MLS gaskets (head). So after the week i drained water and rust compond to my surprise it wasnt rust at all just a dark liquid, so i refilled with clean fresh water 2 more times till it had cleared mind you each time i brought engine up to temp with heater on Hi temp . Now i began to remove old thermostat and there wasn’t the first sign of corrosion in housing neck nor water pump tube . Also stock radiator was clear Im a believer in this Evapu-Rust no need for new rad or heater core also made factory hoses that had never been off on my 1991 3000GT vr4 one owner 32k. Hope this helps. Cheers