Volvo 480 Club Europe

My friend owns a 1992 Nissan 200sx, with a 1.8 turbo engine and an auto box.

Its been off the road for a week now with an overheating problem that neither of us can diagnose - admittedly its not a 480 but its a shame to see a decent car under wraps.

The problem is this - when running (or immediately after a long run) it leaks coolant from somewhere near the bottom of the rad. Its not the bottom hose or the drain plug and we have had the rad out and tested it without finding any leaks. It really does appear to come from nowhere. It also produces a bit of white smoke although not really enough to suggest a blown head gasket. This coolant loss causes overheating.

After several days standing the level in the expansion tank barely moves if at all, its only running the engine that brings on the leak.

Things checked -

Entire cooling system drained and flushed. Twice.

Thermostat working correctly.

Rad cap replaced.

The process for filling the coolant has been carried out according to Nissans workshop manual - no bleedscrew is but we have done everything to the letter to avoid airlocks.

Compression test performed - this was complicated due to a fuel pressure boost solenoid that we were supposed to disconnect but failed to find - we carried on anyway producing results that were all below minimum tolerances but also all near identical. Am I wrong to think that the fact that they were so close would suggest an intact gasket and the low readings were solely due to this solenoid? Surely a blown head would produce low readings in one or two cylinders but all four seems a bit far fetched...

Any tips would be VERY welcome!

Adam

ceck the rad with benzine, it will show leakage if anny. presurize the system to simulate problem conditions - maybe it leaks only under pressure.

How would I go about pressure testing the rad - in particular what sort of pump would I have to use?

There is no Haynes for this car unfortunately...

Adam

If the radiator leaks under pressure, than it will mean the coolingsystem is producing to high a pressure. Mostly this means that the headgasket is gone and the cooling system is pressurised by the cylinder compression.
So probably a blown gasket or a cylinderhead that isn't completely flat anymore.

there's always a pressure in the cooling system, but not a lot. broken headgasket is indicated also by burning smell or gazoline smell in coolant and high release pressure at opening the coolant canister after 10 minutes after engine stop (not accurate at colant leakage) .
the safety cap on the rad or canister should always release overpressure in the system, that's why it's there. broken rad or hose is not a common indication of a fault.

leave the canister open and start the engine cold. continous bubbles in it indicate head gasket.

heat up the engine and closely check the rad, if it is water outside it, change it. use a battery torch , inspect throroughly!

Was a massive airlock.

Turns out that the hot/cold switch is electric despite looking and feeling like the 480's cable type slider. The system was drained and filled with this set to hot but since the ignition was off it was still 'cold'.

Lots of topping up later it runs fine.

Adam