Soggy 911

[Targa Me]

When it rains, sometime, but not all the time, water or condensation gets inside my Dist Cap and causes the engine to run rough until its dried out.
My question is this:
Is anyone using some sort of gasket or seal to keep the moisture out. I'm guessing that the moisture is entering where the cap meets the distributor body.
My P-car is a daily driver so rain is something I need to deal with.
Thanks in advance.

[widgeon13]

I would put a coating of vaseline around the edge and that should keep moisture from entering from that point. Are you sure it's not condensation?

[Targa Me]

Thanks Widgeon but won't vaseline just melt as the engine warms?
Also you asked, "Are you sure it's not condensation?" Unless I'm missing something (and that's quite possible) isn't Condensation, Moisture and Water all pretty much the same thing?

[widgeon13]

It may become more flowing but it should still preclude any moisture from wicking into the cap. By condensation, I meant that it is formed from cooling temps at night forming moisture droplets on the inside of the cap, not from water coming in from the bottom of the cap. Perhaps I should have asked, "Is the water getting in from seepage or condensation?" It's a little easier to solve your problem if one knows how the moisture is getting into the cap. Since you live (or the car resides in So CA), my guess is that's it's not condensation unless it stored in a cool damp garage. Hope that helps.

What causes condensation?

[Targa Me]

It has to be water coming in from outside the cap. The car was in the garage all night and I drove it to work this morning, in the rain. When I pulled off the highway that's when I noticed something wrong. Low idle, loss of power. I revved up the engine for a few minutes and then the engine came back to life.
The engine (3.2) is completely stock and the sensors (all of them) are fairly new. (although that doesn't mean one can't fail prematurely.)

[steely]

What distributor cap are you using? - I wonder if they are all created equal or not. I sprang for the more expensive one last year (930-602-919-00-M14 for no particular reason)- I am wondering if the outside lip is larger. But then again, she's not exposed to water that much.

[Bob Ashlock]

I once had this problem occur and it ended up causing me a big headache. The distributor got "steamed" when I went through a big puddle that splashed water around the muffler, etc. The engine started "cross-firing" because of the wet distributor. By the time I pulled-over and popped the distributor cap to wipe it dry, the cross-firing had caused a blown head gasket. I ended up having to drop the engine and go through all the drama of making the repair, all because of splashing through a puddle. My advice would be to do whatever you can to avoid repeating my mistake! Silicon-seal might be a good idea... it stays 'soft' so you can take the cap off later when necessary.

[Targa Me]

Wow Bob what a nightmare.
It sounds like silicon seal or a RTV might be my answer.
Now this may sound dumb, but I wonder, because the rotor is inside the cap spinning, does the cap need some kind of vent to keep from creating a vacuum within the cap itself? Does that make sense?

Steely, the cap is the one that our host stocks for us.

[Scott Douglas]

This is from the link provided by widgeon13:
Another way in which condensation occurs is on hard surfaces, such as during the formation of dew. Water condensing on a glass of ice water, or on the inside of windows during winter, is the result of those glass surfaces' temperature cooling below the dewpoint of the air which is in contact with them.

I think you went from a 'dry' garage to a 'wet' outdoors and condensation (dew) happened.
We face this problem all the time at work when we move spacecraft from one part of the factory to another. Contamination control engineer has to walk the path and check the dewpoints along the way to make sure we don't have condensation forming in any of the electronics.
Did you reach full operating temp on the way into work?
It was real wet out this morning as I emptied 3/4" of rain from our gauge here in North OC this morning.

[steely]

Originally Posted by Targa Me

...the cap is the one that our host stocks for us.

I think our host stocks 2 types for the 3.2.

Originally Posted by Targa Me

...does the cap need some kind of vent to keep from creating a vacuum within the cap itself? Does that make sense?

Not sure where the vacuum is created in this example, but wouldn't a vent offer a quicker path for moisture to enter?

+1 for the silicone bead barrier idea.

[stlrj]

Originally Posted by Targa Me

My question is this:
Is anyone using some sort of gasket or seal to keep the moisture out. I'm guessing that the moisture is entering where the cap meets the distributor body.
My P-car is a daily driver so rain is something I need to deal with.
Thanks in advance.

Yes, I am and very successfully too.

Here I am giving it all the abuse that mother nature could imagine and my engine continued purring like nothing happened, with me driving off without the slightest miss.





Cheers,

Joe

[DanielDudley]

You are sure it is inside the cap, and not an outside crack or bad wires ?

[tcar]

That usually happens with old wires.

Occasionally a cracked dist cap. Never seen it otherwise. (Unless it's condensation - warm dist is cooled by rain or whatever and the moisture in the air inside the cap condenses on the inside of the top of the cap.

At night, or in a dark garage with the car running, spray a mister over the motor. You should see blue arcing at wires or cap where the problem is.

If you don't have A/C you could always fab a rain shield like the early 912's had.

[rtorres]

Happened to me a long time ago - similar circumstances...turned to be a hairline crack in the cap which I could not see
...the fix was to clean the outside of the cap, dry it off and spray the outside with a clear spray paint. End of problem.

[Techne]

I heard you guys were getting some rain down there. I am really sorry to hear that

Up here in the PNW, I have to deal with this on my daily driver most of the year. I spray a little WD40 on the inside of the cap, it drives the moisture away and seems to work all winter. Give that a try.

[Targa Me]

Yes, I am and very successfully too.

Stlrj, you didn't mention what you're doing to seal the cap, and the answer is......

[stlrj]

Originally Posted by Targa Me

Stlrj, you didn't mention what you're doing to seal the cap, and the answer is......

Originally with Ultra Grey RTV.

RTV Gasket Maker, 3.5 Oz Ultra Gray # 82194 by Permatex

Later I retrofited a larger diameter HEI distributor cap from a Ford Taurus over the OEM cap to deal with the poor sealing qualities of the OEM Beru connectors that would tend to wick water inside causing corrosion and shorts.

[Targa Me]

Thanks stlrj.
Thanks everyone for your input.

[Drisump]

Like the others asked, did you actually find moisture in the cap? Arching wires,cracked cap, even cracked ignition coil, can all cause these symptoms. Cheers