1992 Volvo 940 Non Turbo, Sedan, Overheating, Poor Shifting Issue

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Joined: Mon Nov 26, 2018 8:05 am
Year and Model: 1990 740 GL
Location: Boston, MA

1992 Volvo 940 Non Turbo, Sedan, Overheating, Poor Shifting Issue

Post by bknockenhauer »

Hi All,

Just looking for a little confirmation about what I think is going on with my 1992 Volvo 740 Non Turbo Sedan.

I bought this car earlier this year after my 1990 740 was totalled, it's in amazing shape for its age and the fact that it's lived in New England its whole life. It's got about 165k on it, and was well maintained by its owners (with repair reciepts in the glove for pretty much it's whole life... Besides some corrosion and minor rust in the engine bay, this thing has been running beautifully since I got it.

One week ago I was driving to work and i noticed it was having a hard time shifting between first, second, third. My rpms would drop out/surge despite not moving my foot off the gas. Upon leaving, the car was slipping going into reverse, and I decided to drive home immediately (about 10 minutes tops). This is when I noticed that every time I stopped, the temp guage would pin basically to the red on the dial. As soon as I started moving again, it would be back to dead center, as it always has stayed since I got the car. It may have been doing this longer and I was too comfortable and wasnt looking.

Once I parked, i popped the hood. There wasnt a lot of steam, nothing seemed blown out, but the engine sounded like it was boiling/gurgling, and the expansion tank of coolant was empty. Looked like it had some black sludge in the bottom. Upon further examination after letting it sit for a few days I also noticed my transmission dipstick was bone dry as well.

Today, I changed the thermostat, and filled with coolant to prepare to flush the system. I noticed a grey, milky sludge in the engine that seemed to also be bone dry, instead of green coolant when i took off the thermostat housing. So i poured a gallon in to slosh things around, and was going to drain it when i noticed a puddle of this same grey milk pooling on the street under my transmission. I checked the dipstick, and it was halfway up the stick of the same grey, frothy fluid.

I never noticed any leaks before this so, based on my DIY knowlege of how this car works, I believe the issue is that the coolant and the transmission fluid is mixing in the radiator, which would explain both my overheating issue and my shifting issue. I cant tell exactly where the leak is coming from from the tranny though, its either the send/return line or possible i blew the transmission pan gasket? I'll attach some pics, any confirmation or direction would be hugely appreciated!!! Thanks!
Transmission (right side)
Transmission (right side)
Puddle under car after pouring a gallon of coolant in
Puddle under car after pouring a gallon of coolant in
Expansion tank
Expansion tank
Under thermostat housing
Under thermostat housing

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Post by volvolugnut »

This does not sound good for your engine or transmission. The milky liquid is typical of oil and coolant mixture. The transmission cooler could be cross contaminating the coolant if there is a leak in the transmission cooler portion. I would start with a pressure test of the trans cooler by disconnecting both tubes at the radiator and then clamping hoses to the cooler fittings. Plug one of the fittings and apply low pressure air (maybe 10 PSI) to the other fitting. Try to tee a pressure gauge in the air line. Apply the air and see if the cooler will hold pressure. If cooler will not hold pressure you have confirmed the leak.
Then get another radiator - it must be for an auto trans car to have the cooler. Clean and flush both engine coolant and the transmission. I would drop the trans pan and change the filter after you determine where it the trans has leaked. The trans may be toast.
2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple parts cars.

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