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Old 12-10-2009, 08:16 PM   #1
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Angry 98 Bonneville Transmission Overflow

Hi All,
My 1998 Bonneville is in the shop because transmission fluid starting flowing out the overflow relief on the back drivers side of the engine. No slippage to the transmission or other irregular operation. My car has 69000 original miles on it.

The small town mechanic is telling me that it is probably the plate gasket that has let loose on the transmission because the oil is "foamy". It only leaks with the engine running. Mechanic is recommending full transmission rebuild at a cost of over $2800.

My question is: Could this be weather related?? It has been below freezing for the last 3 days and seems strange that this overflow problem would just suddenly appear. My thinking is that somehow water got into the transmission and froze causing a blockage and making the fluid come out the overflow. Any ideas??

One other question: IF the fluid is restricted to coming out the overflow, can I plug the overflow somehow in order to get the car home???

Any help would be appreciated!!!

Thanks,
Chris
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Old 12-10-2009, 09:21 PM   #2
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If there is water somewhere in there I wouldn't want to just plug it up and keep going, there must be a cause for it getting in there and you want to fix that so you don't end up paying for a new tranny
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Old 12-10-2009, 09:54 PM   #3
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I agree Crunk. Just trying to figure out what would cause it to all of a sudden start overflowing with no loss of performance. I would have thought I would have seen a slow leak if it had been a gasket going bad.
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Old 12-10-2009, 10:24 PM   #4
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How is the fluid level? What color, does it smell burnt?
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Old 12-10-2009, 10:30 PM   #5
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Fluid level was fine when checked at the dipstick but I know I blew at least a couple of quarts out the vent. I thought the transmission was a closed system!?! Never heard of a vent before. Fluid is reddish and does not smell burnt.

I'm having the mechanic do a complete flush and filter change out. Wanted to try the cheaper thing before paying so much for a rebuild.
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Old 12-10-2009, 10:32 PM   #6
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Since I know a couple of quarts leaked out and the level was good at the dipstick, is there a possibility that I might have sprung a leak in the coolant?? That would explain the level not dropping I think. The fluid was darker than normal but hard to tell since there was ice on the road.
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Old 12-10-2009, 10:36 PM   #7
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The trans does not have a vent. There'* a set of lines that go to the cooler, and the dip stick, that'* it. I had a trans leak fluid from the seal where the dip stick goes in. The fluid sprayed all over the exhaust. This seal is a few dollars. Here'* a picture of the seal.
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Old 12-10-2009, 10:38 PM   #8
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Originally Posted by CCCCChunt View Post
Since I know a couple of quarts leaked out and the level was good at the dipstick, is there a possibility that I might have sprung a leak in the coolant?? That would explain the level not dropping I think. The fluid was darker than normal but hard to tell since there was ice on the road.

Do you have pink coolant? Well, some call it orange, but is it Dexcool? Trans fluid is dark red, dex is more of a pink. I would check the coolant level
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Old 12-11-2009, 02:25 AM   #9
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It'* a dark, reddish brown color as far as I can tell.
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Old 12-11-2009, 08:25 AM   #10
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The trans does not have a vent.
Uhmmmm actually they do. Look at the top of the transmission where the sidecover meets the casing. About 1" behind the tallest bump on the casing is a little cap looking item that should spin pretty freely. That'* the vent.

Sounds like you did lose a gasket as the mechanic is mentioning. However with that mileage etc. I'd suggest going in, replacing the one seal (should be easy to get to) and then reinstalling the trans.
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