Trying to diagnose engine problems in a 1992 Volvo 740 Turbo, about 230K (odo broken).

The car came with a history of engine overheating, previous owner had the leaking radiator replaced before realizing the coolant in oil problem, at which time the car was parked and sat for about 6 months.

Drained about 3L of coolant from the radiator, the rest (another 2L, pretty much) drained from the oil pan before oil started flowing. Suspecting the head gasket failure, I took the head off, only to find that the gasket itself was fine. Looked like it's been replaced maybe a few years ago, and no visible signs of damage. The inner plastic cover for the timing belt has melted right between the engine block and the head though to evidence overheating.

The coolant was pretty much everywhere, engine cylinders, exhaust manifold, some minor deposits in the intake ports. Seemed like a major leak, not just a small amount seeping into one or two cylinders, so naturally I'm curious where the stuff was coming from. Couldn't see anything obviously wrong with either the head or the block, and will check for warping once I'll get everything cleaned.

Would appreciate pointers where to look for other sorts of leaks. Cracked block or head? Water pump? (that one seems to have been replaced recently).

Thanks!





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'98 V90 234K '98 V90 157K '94 940 NA 189K

Magnaflux the cylinder head for cracks.

Dye penetrant test for cracks; can’t magnaflux aluminum.

I’ve never owned a turbo red block but I’m wondering if it’s possible for the water cooled turbo to develop an internal leak through which the coolant can find its way into the intake.

Didn't see any traces of coolant in the hoses from the turbo to the intake. The turbo itself also seemed OK (on visual inspection). My guess would be that coolant present in the intake ports could get there if the engine was cranked with some coolant present in the cylinders. Any possibility for the turbo to leak coolant into oil internally? The turbo seems to be Mitsubishi TD05 (hard for me to say for sure, the paint on the label is almost gone). The turbo also says '89, and the head '88, so both might have been replaced at some point (the car was built 11/91).
Thanks!
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'98 V90 234K '98 V90 157K '94 940 NA 189K

Coolant leak into the turbo water cooled housing would put out a smoke cloud at the exhaust.

If equipped, possible oil cooler failure.

IIRC, Volvo went back to using water cooled oil coolers.

Early Volvo 1800 models came with them and when they failed water could get into the oil.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com