Cleaning head before installing valve cover - PeachParts Mercedes-Benz Forum

Graham · #1 10-02-2017, 04:25 PM

In process of adjusting valves on 85 300D, notices that the valve cover gasket sealing surface on the head has a hard black coating in places. Tried painting carb cleaner on and letting it sit, then rub with rag, but it doesn't budge it. Same for brake/parts cleaner.

I don't know if this is varnish or what. I know many of you have these cover off and on more than I have - Have you seen similar deposits? Any suggestions on how to remove?

Pictures below of some of the spots.

jabstick420 · #2 10-02-2017, 04:38 PM

I have the same build-up...

I haven't scraped it for fear of scratching the mating surface and/or dropping chunks of stuff into the engine.

I'd also be curious as to what it is and if it even needs removal...

JHZR2 · #3 10-02-2017, 04:57 PM

Isnt this why you put an ultra thin oat of RTV, shellac, etc. on the gasket face? The VC side is a groove, but the head side is just a flat, so I assume some sealing compound would be good insurance.

Graham · #4 10-02-2017, 05:47 PM

Quote:

Originally Posted by JHZR2

Isnt this why you put an ultra thin oat of RTV, shellac, etc. on the gasket face? The VC side is a groove, but the head side is just a flat, so I assume some sealing compound would be good insurance.

I saw a how-to thread on BW where the owner slathered sealant on ! It's not usually recommended, but I wondered if that residue was from me or shop using a sealant in past. I know I used sealant to hold gasket to cover during installation. The residue from that was a brownish color.

But it is not only right under the gasket, so perhaps carbon or varnish from hot fuel?

If I can't clean up the surface, I might try ultra-thin sealant. I don't want to have to re-install cover! BTDT.

JHZR2 · #5 10-02-2017, 05:58 PM

Quote:

Originally Posted by Graham

I saw a how-to thread on BW where the owner slathered sealant on ! It's not usually recommended, but I wondered if that residue was from me or shop using a sealant in past. I know I used sealant to hold gasket to cover during installation. The residue from that was a brownish color.

But it is not only right under the gasket, so perhaps carbon or varnish from hot fuel?

If I can't clean up the surface, I might try ultra-thin sealant. I don't want to have to re-install cover! BTDT.

Thin is key. Could be a soot impregnated varnish, butvtgen why just there? Id suspect it's some combination of the head porosity with the rubber material.

torsionbar · #6 10-02-2017, 07:24 PM

Quote:

Originally Posted by JHZR2

Isnt this why you put an ultra thin oat of RTV

Ugh, please no. Silicone sealant would be an especially foolish choice here - one stray drop gets squeezed out, and it can plug an oil orifice inside the engine. Engine go boom. I would avoid sealants altogether, but if you have a stubborn mating surface leak, use only a non-setting product like Curil-T or Hylomar Blue.

If the black residue is not causing a leak, I would ignore it. As has been mentioned, the risk of damaging the surface, or of pieces falling into the engine, is simply not worth it.

Graham · #7 10-02-2017, 08:02 PM

Quote:

Originally Posted by torsionbar

Ugh, please no. Silicone sealant would be an especially foolish choice here - one stray drop gets squeezed out, and it can plug an oil orifice inside the engine.

So you think the guy in the link below might have overdone it?

The ultra thin smear we were discussing would not likely squeeze any sealant out but might might help with sealing any imperfections in surface.

https://mbworld.org/forums/clk-class-w209/365344-diy-remove-replace-valve-cover-gaskets-spark-plugs.html

tangofox007 · #8 10-02-2017, 08:39 PM

I would not be so averse to careful scraping. Plenty of cars use paper or cork gaskets for the valve cover: not scraping is not an option. There is also some nasty stuff known as gasket remover that might help.

https://www.permatex.com/products/gasketing/gasket-removers/permatex-gasket-remover-low-voc-formula/

JHZR2 · #9 10-02-2017, 08:43 PM

Quote:

Originally Posted by torsionbar

Ugh, please no. Silicone sealant would be an especially foolish choice here - one stray drop gets squeezed out, and it can plug an oil orifice inside the engine. Engine go boom. I would avoid sealants altogether, but if you have a stubborn mating surface leak, use only a non-setting product like Curil-T or Hylomar Blue.

If the black residue is not causing a leak, I would ignore it. As has been mentioned, the risk of damaging the surface, or of pieces falling into the engine, is simply not worth it.

Not sure if you got the ultra thin part. We're not talking a bead. We're talking the thinnest coat on the basket surface to take up differences on the head if it cannot be cleaned sufficiently. Personally I would try to take a new razor and see what I could get off. But if OP is opposed, so be it.

We're not trying to play hack mechanic here, or create a gasket with rtv in lieu of proper assembly techniques. But these are harder and smaller than most vc gaskets, that op is mating to a surface he seems hesitant to clean further due to risk of roughening or gouging.

If applied properly, there's no chance to extrude a clump big enough to clog anything. We're not talking about running a bead along with the gasket. I wouldnt be opposed to the products you mention either. Its really only there to fill in gaps where there may be a raised edge due to whatever the residues are, that the VC gasket is too hard (even new) to fully adapt to.

Graham · #10 10-02-2017, 11:23 PM

Quote:

Originally Posted by JHZR2

Not sure if you got the ultra thin part. We're not talking a bead. We're talking the thinnest coat on the basket surface to take up differences on the head if it cannot be cleaned sufficiently. Personally I would try to take a new razor and see what I could get off. But if OP is opposed, so be it.

We're not trying to play hack mechanic here, or create a gasket with rtv in lieu of proper assembly techniques. But these are harder and smaller than most vc gaskets, that op is mating to a surface he seems hesitant to clean further due to risk of roughening or gouging.

.

I am not opposed or hesitant to clean further. I was just asking for ideas from others who have done this job more times than I have.

Scraping with razor blade is not practical, particularly around the injectors and at the back. I did try attaching a piece of mildly abrasive fabric to the end of a small paint brush. But even with a soaking of carb cleaner, the black stuff didn't budge. I could make up a mini sanding pad on stick, and use 1000 grit paper.

Any other suggestions?

Diseasel300 · #11 10-02-2017, 11:36 PM

Is the head material cast iron? If so you might try gentle scraping with a chisel. Cast iron is pretty tough stuff, unless you're going crazy with tools, you shouldn't damage it.

Alec300SD · #12 10-03-2017, 01:41 AM

The black coating is oil that has permeated the surface of the cast iron and has been baked in to the point of polymerizing into a hard nonstick surface.
Just like when you season a new cast iron skillet before you use it for cooking.

The black coating is where the VC gasket has failed to seal and allowed the "seasoning" to occur.

Probably the safest and quickest way to remove it is with a drill mounted brass wire wheel and a hand held brass brush for the hard to reach spots.
Use brake cleaner on a shop rag to wipe away the residue the wire wheel treatment creates.

I'd avoid using sandpaper, and also avoid silica impregnated scouring pads.
You want to keep that kind of grit out of the engine.

Afterwards, genuine MB VC gasket and ultra thin smear of black RTV on the VC gasket as recommended by Doktor Bert.
http://www.peachparts.com/shopforum/diesel-discussion/328295-leak-free-617-a.html

Graham · #13 10-03-2017, 09:22 AM

Quote:

Originally Posted by Alec300SD

Probably the safest and quickest way to remove it is with a drill mounted brass wire wheel and a hand held brass brush for the hard to reach spots.
Use brake cleaner on a shop rag to wipe away the residue the wire wheel treatment creates.

I'd avoid using sandpaper, and also avoid silica impregnated scouring pads.
You want to keep that kind of grit out of the engine.

I thought about using brass brush, but concerned about strands of brass getting into engine. Less concerned about any grit coming off 600-1000 grit paper when used with oil lube. Will also try fine synthetic scouring pads and Magic Eraser that I found among our home cleaning supplies.

If the black stuff won't come off, then hopefully a smear of hi-temp Permatex Ultra Grey that I already have will overcome any imperfections.

Almost done with valve adjustment - they needed doing! But noise that prompted me to do it, was due to one bolt missing from air cleaner mount and one failing buffer.

Thanks for input.

torsionbar · #14 10-03-2017, 09:23 AM

Quote:

Originally Posted by Graham

So you think the guy in the link below might have overdone it?

The ultra thin smear we were discussing would not likely squeeze any sealant out but might might help with sealing any imperfections in surface.

Lol, looks like he didn't get the memo either. Not "likely" squeeze out. But you've no way of knowing for sure, because you can't see the inside once the cover is in place. The correct amount to apply is open to interpretation, as that cringe-worthly photo clearly shows. Non-hardening sealer will not cause a problem when a bit squeezes out. Hardening sealer like RTV has a well earned reputation for killing engines. Ultra thin or not, it will still have to be scraped off the next go round, along with the potential for ultra thin bits falling down into the engine. Why risk killing an engine over an $8 tube of goo?

Diesel911 · #15 10-03-2017, 10:12 AM

This could be a duplicat suggestion. CRC makes a Gasket Remover spray (Autozone has it). It has Technician Grade in small letters and Gasket Remover in large letters, No. 05021.
Wipe as much oil off as you can witha dry rag and crefully spray it on and let it sit 15-20 minutes.

Aster that some of the old gasket material may wipe off but it usually takes a little scrapinng mad a lot easier. For metal use a typical dull knife like you would use with your knife fork and spoon. They usually have rounded edges.

Or you can take apart a wooden clothpin and use one part of that to scrape.

The Gasket Remover came out about the time when it became common to use Aluminum parts with precision surfaces on them like intake manifolds and Cylinder Heads. Scrapoing those with a steel scraper often results in gouging the aluminum.

It can be slow and you may need to re-apply a few times but the stuff works.

I use the stuff sparingly as it costs over $6 a Can around here. I have no experience with other brands.