| Transmission vacuum modulator leaking? [message #326958] |
Sat, 09 December 2017 23:15  |
gibsongo
Messages: 116
Registered: October 2012
Location: Montreal West, Quebec, Ca...
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Senior Member |
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Hello all
In the process of putting the coach to bed for winter, a new problem seems to have surfaced. I am getting white smoke (sometimes a lot of it) coming out the tail pipe intermittently. First time I noticed it was after stopping for lunch on a 200 mile drive. Starting back up I had white smoke blowing for longer than I would expect from condensation. It stopped fairly quickly and I did another 100 miles with no reoccurrence. Then yesterday I drove it to the gas station to fill the tanks up - just far enough so that the temp gauge reached its normal operating level. White smoke on starting up, and all the way home.
Today I started the coach and had white smoke for the first 5 - 10 minutes, then it stopped. I checked fluid levels - coolant level seems normal, but ATF was a bit low. I added a half a quart then started up to measure the level again....and the white smoke really came billowing out.
My guess is a leaking diaphragm in the transmission vacuum modulator that is allowing ATF to be sucked into the intake manifold. Does this sound right? The tranny was rebuilt about 8,500 miles ago so the modulator should have been replaced at that time. But the engine seems to be running too smoothly for it to be a cracked head or leaking head gasket. Besides, the coolant level is holding steady. No coolant sludge on the engine oil dipstick either.
I know the right thing would be to lift the coach, pull the rubber hose off the modulator and check to see if ATF drips out - but I just have dinky car axle stands and am unwilling to crawl under the coach in my city driveway just supported by the bottle jack. Building ramps is a project for next summer.
So if this diagnosis sounds right to the group I will head to a tranny shop Monday morning. Looks to me like the modulator should be very quick to R&R. at a garage with a good floor jack and a pair of good axle stands. They are forecasting 8 inches of snow for Tuesday so I'd really like to get this fixed and the coach put away beforehand....
Gordon Gibson
1976 23" Norris Upfit
Montreal West, Quebec, Canada
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