Thread: So how much crud can I expect in my plenum?

I had my plenum chamber open about one month ago. It was as clean as a whistle at 170k but I've only had it since 150k. I have receipts to show the plenum was opened about 4 years ago (to renew rocker cover gaskets).

I thought my D1 was low kms! Mine was a 1994 150k when I bought it 7 months ago.

I removed the plenum a couple of weeks ago on the Range Rover (3.5 V8) at 435,000km, to replace the manifold gasket. It was a bit grimey, but there was no build up of anything. It been running mainly on LPG for the last 85,000km.

The service schedule reads "Clean plenum chamber ventilation passageway".
I have never heard of opening up the actual plenum during a service but I know the area around the throttle butterfly gets a residue build up that needs cleaning every 20-40000km.

The sludge and carbon grime was thick in my rocker covers, so much so that the flame trap was blocked, haven't been in the plenum, tho'....

cleaned it all out at and bingo!

GQ

My 3.9 at 80K was covered in a "varnish" coating of oil from the breather, and from I guess fuel reversion.
But it really had no thick carbon or anything.
It cleaned up well with just a spray from a can of carby cleaner.
cleaning off the oozed out sealant between the top/middle and bottom was more of a job.
Depends if you change your oil at 5K or more I guess, although mine had only had 10K changes in the 70 K before I got it.
Regards Philip A

Sounds like its not worth taking off, I can think of bettter things to do, may be some carby cleaner might do the trick.

Andrew, I'm told there is a difference between carby clean & throttle body cleaner, the latter being electronics safe.