1998 C70 Transmission Failure

57wayne · Post by **57wayne** » 04 Nov 2013, 14:36

What came first, clogged cooler that failed the tranny, or failed tranny that clogged the cooler?
Drove my C70 to Hershey last month and noticed slipping when I backed out of the motel parking space 250 miles into the trip. Finished the last 100 miles with similar results, but what felt like the clutches grabbing on a right turn. Fluid check had it down 2 quarts! Fluid sprayed under the car pretty well but not clear where it was coming from. Loaded up and headed home, took it easy with a friend following. No problems except one funny shift about 45 miles from home. Parked in the driveway near the barn so the drips would be on the gravel.
A week later went out to move it inside and find that leak. Moved 6 feet in reverse and 'thunk' engine shut off. Restarted, really quiet now...no reverse...no drive...no low...no nothing!
Swapped the transmission and the fluid was black (had not been prior.) Checking the tranny cooler, radiator cooler was clear (new radiator) but the accessory one down under the bumper in front of the other coolers, was totally clogged. What came first, clogged cooler that failed the tranny, or failed tranny that clogged the cooler?
Right now, I have the separate cooler bypassed. I don't tow, and don't drive it hard, but I have had 3 98 C70 coupes with this same cooler. I do not find any listing for it, and maybe it was discontinued by Volvo a couple of years ago? Do I need it with the radiator cooler?

Post by **jblackburn** » 05 Nov 2013, 07:56

I would think that the cooler clogging never allowed the trans. fluid to be cooled off, causing the failure. I guess the question would be: why was it clogged in the first place...small tubing? Maybe a clutch was failing in the first place.

I have never seen those coolers on a 1998 before, but then again, I've never looked at a C70 under the hood. However, for most hard driving - mountain climbing, heavy stop-and-go city traffic, etc., the heat exchanger tube in the radiator is mostly insufficient. I have seen fluid go dark in as early as 20K and as late as 40K on my T5.

57wayne · Post by **57wayne** » 05 Nov 2013, 12:32

I will pull the cooler and find out the cause for the clog. Meanwhile, what is the recommended cooler to use? I can see generic tube-fin units that look like refrigerator condensers, and some plate units that look pretty dense, but not sure how efficient. Recommendations? (Will also tear the old transmission apart to find what let go. Thinking with no place for the flow to go, the fluid was being forced out somewhere unnatural!)

57wayne · Post by **57wayne** » 06 Nov 2013, 20:42

The existing cooler is listed as "Extra Oil Cooler" PN 8618347, and there is a kit that includes the cooler, hoses, clamps etc. Looks like a Volvo dealer only part as I don't see it on other sites. Fits S70, V70 1997 - 2000, C70 Coupe 1998 - 2002 and C70 Conv 1998 - 2005. Was able to blow air through it last night. Not sure why it was not blowing through previously.