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Re: [GMCnet] Transmission vacuum modulator leaking? [message #326965 is a reply to message #326961] Sun, 10 December 2017 05:18 Go to previous messageGo to previous message
GMC.LES is currently offline  GMC.LES   United States
Messages: 505
Registered: April 2014
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Senior Member
If your engine was consuming enough coolant to make white smoke, you would likely detect a sweet odour to the exhaust.

I think you'll be lucky if a trans shop here in Montreal has a modulator in stock. No demand up here due to salt & rust taking out our vintage vehicles prematurely.

I would disconnect the vacuum line at the carb, and verify for presence of fluid. If the problem is related to the modulator, I'd be inclined to leave it disconnected and park the coach as is for the winter, making note that the modulator needs replacement. It will be much nicer to work on the coach in the warmer spring weather.

Les Burt
Montreal
'75 Eleganza 26'


> On Dec 10, 2017, at 12:27 AM, Jim Kanomata wrote:
>
> There will be evidence there.
>
>> On Sat, Dec 9, 2017 at 9:24 PM, Jim Kanomata wrote:
>>
>> Just disconnect the Vac hose at the intake and see.
>>
>>
>> On Sat, Dec 9, 2017 at 9:15 PM, Gordon Gibson
>> wrote:
>>
>>> 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
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>
>>
>>
>> --
>> Jim Kanomata
>> Applied/GMC, Newark,CA
>> jimk@appliedairfilters.com
>> http://www.appliedgmc.com
>> 1-800-752-7502
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

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