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Q: Condensation in Distributor Cap on 1998 Volvo V70 XC

My Volvo has a problem with excessive condensation forming in the distributor cap. I can't figure out where the moisture is coming from , especially since it has not been driven in any rain or snow since the problem started. The cap itself appears to be in good condition, with not chips or cracks and the ventilation slot are all clear and clean. This will happen just about every time the engines cools down. Dry out the cap and it runs like new. I have NEVER seen this before. Any ideas?
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This is a weird problem. I have a few questions:
Did you do any work to this right before this started happening?
Did this just start happening out of the blue?
Are you using a Volvo cap and rotor?
Is there any oil leaking from the cam seal behind the cap?
The original part from Volvo is a Bosch part I believe, so as long as it is a OE quality part, that should be OK.
What are you referring to when you say "ventilation slot"?
Does your cap look like this?
That all makes sense. That oil seal doesn't really "seal" that much oil from escaping, so it actually might be allowing vapors from the crankcase to enter into the cap, Bingo, Moisture! Replace that seal and I bet it will fix the problem.
Nice work, let me know if that fixes it, and don't hesitate to ask any other questions, I worked on these cars for 15 years so I know them very well, however this is a first!
Have a good night.
Hey Bret- No, I hadn't done any work to the engine prior to this happening. It did just start doing it one day. It has a Bosch Cap and Rotor and both are like new. I see no oil leaking the bottom, inside or out, but I will take a closer look today. The first time it did it, I thought it may have been from sitting a few days. I then did all that PCV work and just this morning I didn't get a mile from the house and it starting sputtering. I was able to limp it home and used the other car for work, so I'll take a closer look tonight. Maybe it's just the "O" ring seal, but what is even stranger is the condensation is very clean and clear. No oil or sludge. I'm thinking this car is haunted...
Yes, this is the cap that I have. If you were to look at the base of the cap, where it meets the side of the head, there are 6 slots, or grooves for ventilation. 3 on each side. They are at about the 4 o'clock and 8 o'clock positions. I had someone else suggest to just go buy a new cap, which I would certainly do, but that does not explain where the moisture is coming from.
Bret- Here is the latest. When I got home today, I pulled the cap off and as I suspected, it was very wet. I dried it off, put it back on and viola! ran perfect again. This time, I let it come up to operating temp. (I took the airbox off so I have some room to work) I shut the engine off and immediately took the cap off. The sunlite was hitting it just right and even though it almost nothing, I saw a little vapor coming out of the top of where the cap mounts. It wasn't much, but I can see where it could build up in the cap. I expect that the seal there is bad. How fun will this be to change?? Or should I do what my racecar buddy suggests and just a drill a couple of air holes in the cap? (That just sounds so hillbilly...)
OK- Final update for the day. After dinner, I got a little more curious, so I popped off the mounting plate for the rotor and believe or not, the camshaft seal was just sort of floating in there. It looks pretty well spent, so I'll stop off at Volvo tomorrow and pick one up. The strange thing is, is that there really wasn't much oil at all coming out of there. Maybe because that this the highest point of the head? I am a little concerned with the amount of moisture coming from the oil, but I have no "Milkies" going on at all. I just want to button this thing up and get rid of it at this point. Stay tuned...
Well Bret, it looks like that was the problem. I got the seal from the Volvo dealer and installed it. I've driven the car for a few days and no moisture problem in the cap. I suspect that prior to changing out all of the PCV system components, the crankcase pressure was so high that it blew that seal right out. I noticed that the rear seal is leaking pretty severe also. I'll probably have the dealer repair that. That is a little deeper than I care to go.
Thanks for all of your help.
I have been scouring volvo sites for 3 days and nights insistent on finding the cause of my misfiring 98 xc70. What came on immediately was ignition misfire at highway speeds on a frigid NY morning commute. Apparently after the seal couldn't take the excess pressure from the clogged PCV system. I took the dist cap off and a little steam was coming out of the head. seal was popped in back.
Your decription was the same except I saw a bit of fresh oil on the head below the dist indicating an issue right there. I was first guided to the widely posted MAF sensor route as the culprit, I simply would not buy it and did my own research to find your postings. The MAF is either going to work or not and rarely do they foul.
Thanks for posting!
Turbo Brick
Glad to have been able to help. Those Volvo PCV systems were WAY over-engineered. They have been the cause of many bad weekends to people. It's amazing to see the oil trap and how totally plugged they can get. Not an expensive fix if you DIY, but it will take a good full Saturday and min. of 6 beers. Good luck, Brian
MANY THANKS, Brian! And for the helpful replies. This was a Godsend. Apparently not a common problem, as this diagnosis was nowhere to be found on the popular Volvo forums, at least that I could find (I added this Repairpal link to my thread at
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