This question isn't specific to MB's but seeing as how this forum has the most knowledgeable folks, I figured I'd ask it here.

So it's pretty simple; if I have a transmission cooler and it gets plugged up, what happens? Let's assume there is no pressure relief valve in the system, just the trans and in/out lines going to the cooler (no thermal bypass valve for cold startup).

Does it just lose the cooling function or ?

Thanks!

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1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?

My thinking is that even though there is considerable pressure going through the cooler, it is not sufficient to blow the system. It just won't circulate.

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Junqueyardjim
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1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

As I recall, the cooler is downstream of the pump.

So, in order to pressurize the valve body, the fluid first passes through the cooler. In a factory system, the thermostat would bypass, or short curcuit the cooler, which would still allow flow from the pump to the valve body.

So, if you have the cooler hard plumbed into place, without a thermostat, then yes, the plugged cooler would reduce or stop the flow of oil. Low/no oil pressure would not allow the trans clutches to engage sufficiently to provide drive to the output shaft.

All factory oil coolers will have a thermostat. It is preferred to add heat to the trans fluid to bring it up to operating temperature, before opening the t-stat to the cooler.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Excellent, this all fits well with the bits and pieces I've found.

Thanks!

__________________
1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?

Are you sure? I stupidly started the engine with the radiator out after the car had sat a couple of days and dumped a few quarts of ATF. Wouldn't a thermostat have restricted flow through the cooler?

And with the Caravan and Suburban, I use the cooler loop to flush the fluid since they don't have a TC drain. I do this with a stone cold engine, transmission and fluid.

And I expect the coolant heats up more quickly than the ATF, certainly more quickly than engine oil, so having the cooler function all the time might get ATF to operating temperature more quickly.

Sixto
87 300D