Condensation in distributor

[HonkersH5]

I'm having constant problems with condensation forming in the distributor cap. I always cover the electrics when I wash the car and never take it out in the rain so why is condensation forming and is there a long-term solution for this?

[MarekH]

It's exactly the same as condensation inside a house. Warm air holds more moisture than cold air and it's warmer inside the distributor than it is on the outer surface of the distributor cap, so any moisture trapped inside condenses onto the inner surface of the cap as it cools down.

Later (but still pre-Marelli) distributor caps from an xjs had a pair of vents on them. One had a simple air filter on it and the other connected to the vacuum system. That draws fresh air through and removes any crankcase gases if they get through the bottom.

kind regards
Marek

[lesxjr]

Given that you say it's a constant problem, you've obviously had the cap off a number of times to have noticed it re-occurring, and given that the cap is sealed with a big O ring (is yours still present?) and that the engine is not exposed to external water (washing/rain) then the question is where is the moisture continually coming from? Is there any cooling water getting into the oil, ie any other obvious signs such as white/cream sludge/mayonnaise present at the breather or in the air filters etc.
Les

[MSM]

You don't say which engine it is, 6 or 12 cylinder?

I had a similar problem with my S2 6 cylinder engine which turned out to be a very small leak from the radiator hose to thermostat housing above the distributor. Corrosion on the stub pipe allowed coolant to leak out and drip onto the distributor cap and end up inside.

[AussieEtype]

You don't say which engine it is, 6 or 12 cylinder?

It is in the Series 3 section - so a V12.

I have had my V12 E-Typefor 42 years, in Europe and Australia, and never had a condensation issue, I would say that there is a problem causing this. Further investigation is needed.

[HonkersH5]

Later (but still pre-Marelli) distributor caps from an xjs had a pair of vents on them. One had a simple air filter on it and the other connected to the vacuum system. That draws fresh air through and removes any crankcase gases if they get through the bottom.

Would this cap fit on a Series 3 E-type?

[HonkersH5]

Given that you say it's a constant problem, you've obviously had the cap off a number of times to have noticed it re-occurring, and given that the cap is sealed with a big O ring (is yours still present?) and that the engine is not exposed to external water (washing/rain) then the question is where is the moisture continually coming from? Is there any cooling water getting into the oil, ie any other obvious signs such as white/cream sludge/mayonnaise present at the breather or in the air filters etc.
Les

This is at least the third time the problem has presented itself and each time it's been dealt with by a mechanic who hasn't offered any explanation for the frequency of the issue. My mechanical skills are limited but I'm baffled by the question of where the moisture is coming from.

[abowie]

https://www.sngbarratt.com/English/#/UK ... r%20cap%60

This is the vented cap, fitted to XJS.

It doesn't say it is suitable for S3 E but it does say that it fits the 35DE12 distributor which I think is what you have.

I don't know enough about the S3 cars to know if this sort of condensation is a common problem with them. I did wonder whether you have a head gasket problem.

Others will know better than me.

[Brewer]

I had a similar problem after washing the engine though the distributor was covered (not well enough, apparently). I found the gasket had a tear in it - it doesn't take much! I was told that Lucas sometimes did not use a gasket but one was included with the new cap I ordered.

[42south]

Hi
Marek is right on the money.
Jaguar acknowledged the problem in the later V12s with the vented cap.
Apparently there had been reports of exploding distributor caps when gas came up the drive shaft into the cap, then the subsequent spark ignited them. There is a seal on the bottom of the distributor drive shaft that can wear and allow gas int the cap, it is easily replaceable.
I had the problem with my V12, the vented cap cured it.

[HonkersH5]

I really appreciate all of the advice here. SNG Barrett says the XJS vented cap won't fit my distributor which according to my repair manual is 36DE12 rather than 35DE12 but I think I'll order one and see how it goes. There's also the suggestion that there might not be a gasket between the cap and the distributor, and there's certainly not one shown in the parts manual so that's another avenue worth exploring. In the past, whenever this problem has presented itself it's been dealt with by a mechanic so I can't say for sure if there's a gasket or not. What I can say is that it's time for me to put my fear aside, stick my head under the bonnet and, within reason, start pulling things apart. Many thanks to all of you.

[lowact]

Also check yr crankcase ventilation system, if this is clogged, not working as it should, a direct consequence could be more condensation in your distributor.

Next I’d try the distributor cap gasket, if air can’t get out, condensation can’t get in? Its not an o-ring, it’s the perimeter of this:

My understanding, such gaskets were not part of Opus distributors (35DE12). T’was not till about 1986, the CEI ignition system for the HE engines, the 36DM12 (vacuum advance) distributors had dedicated ventilation system due to the increased amount of piston blow-by from the high compression engines. It does fit the earlier distributors also.

There is a seal on the bottom of the distributor drive shaft that can wear and allow gas int the cap, it is easily replaceable.

To repair the distributor shaft seal you have to dismantle the distributor, including remove/replace the drive gear. The seal is NLA, solution is to replace the bearing with a modern sealed bearing, to fit this you have to machine the distributor housing.

[HonkersH5]

Many thanks. I now have a vented cap so fingers crossed the problem will go away!

[abowie]

The seal is NLA, solution is to replace the bearing with a modern sealed bearing, to fit this you have to machine the distributor housing.

If you do need to do this it's pretty easy.

I did a test run on a scrapped dizzy body I have. All you need to do is deepen the recess for the bearing; from memory from 0.250" to 0.375".

[42south]

The final step in fitting the vented cap to the Dizzy involves providing slight suction through the cap. Jaguar did this on the inlet side with a fine rubber tube going to a small filter tied somewhere near the firewall. I used a small ride on mower filter on mine.
The suction was provided by using the same fine rubber hose to one of the small tubes set into the underside of the inlet air cleaner.
Someone can probably provide a photo showing this.

[HonkersH5]

"The suction was provided by using the same fine rubber hose to one of the small tubes set into the underside of the inlet air cleaner.
Someone can probably provide a photo showing this."

Yes please! If anyone has a photo it would be an enormous help. I can't see where the connection needs to be made.

[MarekH]

Plug it into any of the manifold vacuum sources. Any of the four three branch intake manifolds will do. Just look at an XJS parts manual or an XJS engine bay and translate that to your car.

kind regards
Marek

[lowact]

Imo air cleaner would be better than inlet manifold. Connecting to the manifold would be creating a major vacuum leak. Unless you built in a tiny orifice; then it would be only a minor vacuum leak.
On the cars this system was designed for (XJ12S3/XJS) it connects into the hose from the air cleaner to the extra air valve.
How to connect on an e-type; there’s no proper way because its not a proper thing to do; you’re treating the symptoms not the cause.

[MarekH]

That sounds very sensible. This was only there to draw a small amount of air through so crankcase vapours didn't end up collecting in the cap. Your reason for doing it is different and at the end of the day, that's not how moisture/condensation got in there.

kind regards
Marek

[HonkersH5]

I can see that there is a vacuum pipe attached to each air cleaner (item 4 in attached scan). Is this where I connect the hose from the side vent on the distributor? If so, do I need to fit a t-junction?