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Changing valve/rocker arm cover gasket-what cleaning/service should i do while cover is off?

1990 jeep 4.0 L in-line 6

what should I clean and with what should I clean it?

I m sure there is some gunk to clean but not sure of how to go about it

Remove valve cover.

Remove the old valve cover gasket/sealant from valve cover/head.

Apply gasket/sealant to valve cover.

Reinstall valve cover.


thanks tester…

I m gonna clean the gunk. the question is, will I do it right or not?

If there’s sludge on the valve train/head don’t touch it.

I won’t even do it.

Because of the valve springs, rocker arms, and push rods, it’s impossible to remove the sludge if it’s disturbed.

Then when the oil flows in the head again this sludge can be dislodged, go down the drain back holes in the head into the oil pan and plug the oil pump pickup screen.

Just check to see if the oil drain back holes are open and put the valve cover back on.


+1 for Tester…

what about using top engine cleaner and changing oil

I won t be able to stand not touching it. it will drive me nuts.

my son saw me looking at a tool out of place the other week and said, “that tool sitting there is driving you crazy isn t it”? he knows me too well.

I can be sloppy in some ways, but my work area and tools have to be just so. and I might procrastinate, but once I do something I don t want to do it half way

A top engine cleaner cleans the injectors and intake valves.

It has nothing to do with the valve train.


Most of us in the business take great care to NOT clean, touch, or disturb any gunk or sludge that’s built up on the valve train. Remove the valve cover, clean only the mating surfaces, and install the cover with a new gasket.

Cleaning anything else other than the return passages is asking for trouble.

@WESW; no matter what you apply to the gunk, you will not disolve the tar like clumps. When they drain down to the pan, it is impossible for them to all flow to the drain plug hole.
Even if you removed the pan, some chunks will remain in the return passages where the oil drains back to the pan.
When you finish and start the engine…the sludge will plug the screen Plug lifters, and any grit could damage bearings.

I know you feel that these chunks will disolve and when you do the next oil change, it will all be removed. But this sludge is hard to disolve and you will do more damage than if you just left it alone.

Look at it this way. When you clean the valve cover and place it right side up to drain you will flip it over and you will find more to clean out. You never really get it all and you finally say…“thats enough”.
So even if you could place a tank under the engine without the oil pan and pumped parts cleaner thru it, and sprayed down the vally for an hour, you’d never get it all.

Leave well enough alone and settle with it the way it is.
If you want to clean something, go shampoo the living room carpet, your wife will love it.


I concur with the others, besides preparing the gasket surfaces for the new gasket, the less you do once the valve cover is off, the better. The most important objective is to not allow anything drop into the insides while the valve cover is off. As there’s a lot of places it can lodge and jam that will be very expensive to fix. While the valve cover is off on my Corolla I usually put a piece of clean cotton cloth over the insides until I’m ready to re-install the cover.

There is something you could do though. You could clean the valve cover before removing it, so no dirt/gunk drops into the insides during the removal process. Maybe give the valve cover and associated area a good shop vac treatment before undoing anything.

Oh, one more thing, if you have adjustable valves, you could measure the valve clearances while the cover is off.

but, but. but…

okay, I get it. thank you.

is there a benefit to using top engine cleaner at all in my case?

will high mileage oil have any benefit or cause any problem?



Is that clear enough for you?


If you guys had to replace a head gasket, and therefore had to pull the valve covers, and heads, AND let’s say you pulled the oil pan, would you STILL not clean gunk out?

that s what I m talking about. will it help much with my injectors and intake valves.

I said I get it about the valve train. I thought I made that clear when I said " okay, I get it. thank you"

never mind…

I don’t mean to hijack the thread, but, knowing that I was planning on changing my head gaskets, and knowing my engine has sludge, I wanted to pull the oil pan as well and take the opportunity to really clean out the engine.

help yourself fender, its all related


If you have to remove the head an there’s sludge on the head it would be placed in a dip tank of solvent to remove the sludge.

But we’re just talking about removing the valve cover.


IMHO if the owner plans to or is willing to pull the pan, sludge should be cleaned from the area under the valve covers, the returns should be cleaned out, and the pan and pickup cleaned. Fender, I support your planned project.

If not, than I agree that it’s better to just replace the gaskets.

I’m not recommending this, but when my dad used to change the oil in his fairly new (at the time) mid-60’s F100 pickup truck he’d drain out all the oil, then refill the crankcase with diesel fuel, and idle the engine for a few minutes. Then he’d drain the diesel fuel out and proceed with changing the oil filter and refilling with fresh oil. His theory was that this process cleaned the engine insides better. I did notice quite a bit of black gunk would come out with the diesel fuel. It didn’t seem to do any harm, and might have done some good maybe. But that was a 1960’s engine technology. I wouldn’t try it on a modern engine unless I was in a “devil-may-care” experimenting mood.