Downshift Concerns

[MattDoscher]

'91 Grand Marquis, stock SEFI 302, AOD tranny, and dual exhaust. Any thoughts on what would cause a plume of white cloud/steam to emit from the car when I downshift out of overdrive into 3rd or 2nd when I get on it to get up a hill or merge onto the interstate? Under normal/light throttle driving this does not occur even if I downshift out of overdrive into 3rd and not get on it, no white cloud is apparent. It's not an oil burning cloud as it is bright white and dissipates like it's steam or some type of vapor coming from the engine or tranny. My friend was behind me when this happened and he said it smelled like burning rubber. Another friend said it smelled like gas. Could it be the bands inside the tranny slipping during high revs in 2nd or 3rd causing this white cloud that dissipates? Anyone else experience this weird occurrence?

[DerekTheGreat]

Well, if the trans was leaking you'd see puddles when parked and the dipstick would be low, only way it would smoke.

Light oil burning is often white, so is coolant. Is your coolant level high or low or contaminated? When coasting there is a lot of vacuum inside your engine, as it is trying to pull air in the cylinders from anywhere possible. If your valve seals are bad & your guides sloppy, it will pull air and oil in from them and youll see that burn when fuel is reintroduced to the combustion chamber when you get back on it.

[MattDoscher]

There are no engine or tranny leaks, engine oil level is good, coolant level is high in the radiator but has the stock recovery container that is at the appropriate level. Again, this white cloud dissipates and does not hang around like you would expect if it were burning oil.

[VicCrownVic]

I'm not sure that it would be caused by the trans slipping, whether it is or isn't slipping.
Can you reproduce the cloud if you stomp on the throttle while the car is parked?
Does it seem to be more on one side or the other of the car?

My thought is perhaps a pinhole leak in a coolant hose.
If it's mainly on the passenger side, it could be one of the heater hoses. If it's on the driver side it could possibly be the EGR cooler lines (those are fun to get at without removing the upper intake.)

I once had a pinhole leak in one of the small hoses at the water pump. I couldn't pinpoint it until I opened the hood and pulled the throttle open by hand. Each time I would rev it the coolant would shoot up, the cooling fan would then blow it back all over the open hood. For whatever reason I guess it was a small enough pinhole that I couldn't see the leak unless I got on the throttle.

This may not be your issue, but it should give you something to rule out. Check all the coolant hoses.

[kishy]

There is the possibility that you're looking at residual moisture in the exhaust being suddenly evaporated and pushed out by the sudden increase in temperature associated with a sudden rise in engine RPM and load. However, this would hardly be noticeable.

There is also the possibility that your intake gaskets are bad causing any of #1, 4, 5 or 8 to pull coolant from their adjacent coolant passages and burn it. It doesn't need to be a lot of coolant to be visible, but you'd probably be adding some every 3-6 months.

There is only one band in an AOD, for OD, so it's out of the picture for 3 and below. However as with any time a question about the AOD comes up, make sure the TV cable is reliably attached with a correct grommet/bushing.

Thinking outside (or under) the box, it might be something happening inside your cats...cat material burning? Broken apart cat dust being blown out forcefully by the sudden increase in exhaust flow? I'm reaching here, but it's not so unlikely with a car this age.

[MattDoscher]

Can you reproduce the cloud if you stomp on the throttle while the car is parked?
Does it seem to be more on one side or the other of the car?

I don't really want to high rev the engine with no load on it. I can't tell if it is on one side more than the other, I just see it from the rear view mirror. I haven't noticed any coolant leaks at the hoses, but also haven't given them a close inspection either. I do notice on occasion (more pronounced in the winter) the EGR spacer gasket will leak some and leak coolant on top of the valve cover.

cat material burning?

Could be possible I guess, I don't know. They are the original cats on it. When this happens there are no strange noises, pinging, or anything. The check engine light doesn't even come on.

[Tiggie]

+1 eating coolant.

Go for a normal drive and then let it sit overnight. Should pull a slight vacuum when you open the radiator cap. If not, it’s very likely leaking somewhere.

[DerekTheGreat]

My firebird poofed oil exactly like you described, whiteish mostly, sometimes with a tinge of blue. Bad valve seals. Would not burn while cruising. Reving it up in neutral and then letting RPM fall to idle and revving up again should produce smoke if it oil was getting past the guides/seals or rings. Might also puff if coolant is getting past the headgasket or somewhere else. Worth a shot and won't hurt anything.

But I suspect you are eating coolant from somewhere. Keep an eye on the level, keep an eye on the oil dipstick too. When I redid the EGR/Throttlebody gasket on my '88 I noticed a nice clean streak where coolant was leaking into the intake. Never saw it out the exhaust. I only fixed the issue when I saw it leaking onto the valve cover. Not surprised it isn't setting the CEL.

[MattDoscher]

Thanks everyone, I'll start investigating coolant hoses and other sources for coolant leaks.

[Kodachrome Wolf]

That TB gasket could also be suspect if it’s seeping through and leaking into that.

[87gtVIC]

Chock front wheels, have your foot on the brake (hard) and put it into gear and give it some gas. Have someone inspect whats going on behind the car, under the hood (from the side of the car).

[MattDoscher]

When I redid the EGR/Throttlebody gasket on my '88 I noticed a nice clean streak where coolant was leaking into the intake.

That TB gasket could also be suspect if it’s seeping through and leaking into that.

Took the car over to my favorite shop and sure enough the paper gasket btwn the throttle body and EGR spacer had broken down enough to allow coolant into the throttle body. I could see a clean streak on the bottom of the throttle body right toward the butterfly. Replaced that gasket and the one btwn the EGR spacer and intake with NOS Motorcraft ones.

[87gtVIC]

Did it solve your problem?

[MattDoscher]

I should clarify that the coolant was getting into the EGR spacer not the throttle body, and the clean streaking was on the inside bottom of the EGR spacer not the throttle body as mentioned in my post yesterday.

Did it solve your problem?

I don't know yet, time will tell, but I feel confident that was the issue.