Cleaning exhaust manifold for gasket

[JHZR2]

I have a bunch of threads on my repair journeys, but each one is a discrete question, so I think it’s best in order for others to reference info in the future.

This has to do with prepping/cleaning the head in place, for a new exhaust manifold gasket.

The old gasket was pretty dirty and leaked.

The other day when I was off, I was trying to clean the surface in anticipation of re-installation.

I used paper dry, brake cleaner, carb cleaner, and even maroon scotchbrite and plastic razor blades.

I didn’t get anything that well..

This is where I ended up:

I can still feel a bit of a deposit on the surface with my fingernail.

What else should I try to use, and how good is good enough?

It’s all blind with my wrist contorted backwards. So not very easy to do…

Thanks!

 

[CleanSump]

If the head is aluminum I've always just sprayed brake parts cleaner and scraped carefully with a razorblade. Wipe with paper towels or clean rag. You don't have to get all the black stain out for it to seal.
For cast iron/steel, like the exhaust manifold itself, I wire brush on a drill. Again, it may not come up all pretty shiny silver color, but you can get it down to steel, get the carbon off, and it will be smooth. Discoloration (vice carbon on the surface) won't stop it from sealing.

 

[MaximumMini]

CleanSump summed it up good above.
All I could add is .....

When I have a gasket surface on an exhaust (or intake) like that, I try not to use thin, flat metal gaskets. Instead I try to get thicker, high temperature compressible gaskets that will conform to the deformities on the surface. I have a large sheet of gasket material that I often use to make custom gaskets. It is a high temperature non asbestos material sandwiched between two metal sheets. I forget who made it.

 

[clinebarger]

Looks acceptable to me, The manifold itself is more of a concern (It being flat)

 

[PontiacHO]

Looks acceptable to me, The manifold itself is more of a concern (It being flat)

This… lay a straight edge across the mating surface to ensure the exhaust manifold isn’t warped.

 

[TacoFergie]

I have always used Scotch-Brite (3M) white bristle discs to remove excess gasket material and to prep the surface, clean with brake clean after. They do offer yellow and green discs, but those are a bit aggressive on aluminum. I use it on my 90 degree grinder at a low speed with minimal pressure applied. They last a really long time if used properly, maybe 2 years in daily use. Higher speed and more pressure just wears it out faster without any advantage to removal speed or surface prep. Do not get off brand ones, they wear out really fast and the bristles tend to break off easily.

I've even used them to prep the head and block surfaces (without sending anything to a machine shop) when doing lifters and cam replacement on LS engines, not a single head gasket failure yet.

https://www.amazon.com/Roloc-Bristl...205462&sprefix=ROLOC+BRISTLE+,aps,365&sr=8-11

 

[JHZR2]

I have always used Scotch-Brite (3M) white bristle discs to remove excess gasket material and to prep the surface, clean with brake clean after. They do offer yellow and green discs, but those are a bit aggressive on aluminum. I use it on my 90 degree grinder at a low speed with minimal pressure applied. They last a really long time if used properly, maybe 2 years in daily use. Higher speed and more pressure just wears it out faster without any advantage to removal speed or surface prep. Do not get off brand ones, they wear out really fast and the bristles tend to break off easily.

I've even used them to prep the head and block surfaces (without sending anything to a machine shop) when doing lifters and cam replacement on LS engines, not a single head gasket failure yet.

https://www.amazon.com/Roloc-Bristle-Disc-Grade-Size/dp/B06WVJ4166/ref=sr_1_11?crid=1MFPBDIKWJA1K&dib=eyJ2IjoiMSJ9.rOTEsJKzs7qqz8u4WAbs-CchToydqD4V9rAGZQuepLNkxsqdOPcG68oOnLlE_g1S7iGa_DoMt22Wvy_id5pLygVg7FcgpvRAmuLGJ74FxlRkfoZyFprb1FgCP5aOqsAnm-BhXGUC2BPQJt0ngox_4czcfu1CV19xISEM1g9sRoj43jDsbxU8Ki-6FSZH6OWsrDtDWxmXnHlNCvI29Gqn0tIOBzeFNKw05Hr-z75edLU.W9765VPehSFeNGE2QGWmFn54jWctVLHNfDrMb23kXB0&dib_tag=se&keywords=roloc+bristle+disc&qid=1763205462&sprefix=ROLOC+BRISTLE+,aps,365&sr=8-11

I got the 120 like you said, but frankly are a bit afraid to use it.

I found a Chinese 220 on Amazon and used that instead. I guess 3M doesn’t make finer than 120, at least that I could find. I know your warning about off brand, but even though I’m going slow and light, it’s just concerning….

I’m running it on slow. It has worked on many spots. Feels cleaner. Not perfect.

How good is good enough??

 

[paulo57509]

Razor blades and green scotch-brite pads works wonders on seal packing ("hard" silicone on aluminum) - with some patience. It didn't have to be totally clean, but these were in a spot where getting to it is a real pain to reseal.

 

[JHZR2]

Razor blades and green scotch-brite pads works wonders on seal packing ("hard" silicone on aluminum) - with some patience. It didn't have to be totally clean, but these were in a spot where getting to it is a real pain to reseal.

View attachment 311525View attachment 311526View attachment 311528

That’s beautiful work.

I certainly would want to be extra careful for spots where there could be liquid leaks, etc.

For this, there’s a gasket, no chemical seal. But my primary issue is that I’m afraid of aluminum. It’s soft, I could abrade it down, and so it’s all a risk to me. Especially when it’s angled downward in a tight spot.

I did build the courage to use my 120 disc…

I am willing to try a razor blade. That’s a lot safer than more abrasives in this case, IMO.

 

[Exhaustgases]

Wow, now you have some nice high and low areas. Just me, I would not and will not ever use one of those power tools on a gasket surface.
For a rusty old chunk of steel then sure.

 

[JHZR2]

Wow, now you have some nice high and low areas. Just me, I would not and will not ever use one of those power tools on a gasket surface.
For a rusty old chunk of steel then sure.

That was a concern. I used no pressure and maybe ten seconds per hole.

There were “high and low” spots before from the ridges of the OE gasket on the head after 34 years. I wasn’t grinding on the surface.

Frankly, the deposits weren’t coming off without some help.

Lighting makes everything look worse, but the deposits were easily felt with a fingernail.

 

[TacoFergie]

That was a concern. I used no pressure and maybe ten seconds per hole.

There were “high and low” spots before from the ridges of the OE gasket on the head after 34 years. I wasn’t grinding on the surface.

View attachment 311566


Frankly, the deposits weren’t coming off without some help.

Lighting makes everything look worse, but the deposits were easily felt with a fingernail.

Regarding the 120 vs 220 disc, I've never had an issue with the 120. Rule #1 with any forced movement abrasive is not sit in one spot or apply much pressure. I don't know how 3M quantifies their abrasive ratings on bristle discs? Because 120 sounds a lot more aggressive than the results appear during use. When I was a tech it was recommended that I use White (120) for aluminum, Yellow (80) for cast iron/steel and Green (50) was pretty much reserved for corrosion removal on non-sealing surfaces. Though I never knew or looked at the abrasive ratings, just going off what master techs taught me. One thing is for sure, those bristle discs are a game changer compared to the fiber backed scotch brite pad style discs since those clogged and wore so fast. Plus it was easier with those to creat high and low spots on a sealing surface since they are less forgiving to pressure applied.

As far as the pitting from the gasket, that's pretty normal and not much you can do about it. If you use an OEM metal layered gasket, you'll be fine.

 

[TacoFergie]

Razor blades and green scotch-brite pads works wonders on seal packing ("hard" silicone on aluminum) - with some patience. It didn't have to be totally clean, but these were in a spot where getting to it is a real pain to reseal.

View attachment 311525View attachment 311526View attachment 311528

Those surfaces look great and NOTHING beats Toyota FIPG in my opinion. Honda bond and GM's sealant are great too, but something about FIPG just works better.

I have nothing against a razor and scotch-brite pads or other processes. But in a shop environment, speed and consistent results is key. Like that upper coolant passage with a white disc would take less than 30 seconds of work to get the same results as you have there. Now for timing cover, oil pan, valve cover, intake, exhaust gasket surfaces, etc goes exponentially faster. It also gives a very light cross-hatch surface that allows sealants to seal really well. Plus in many locations it's easier to get a 90 degree rotary tool in than a blade and scotch-brite. Hands get cramped quick too when wrenching for 8-10hrs a day doing multiple jobs while trying to manually scrub stuff.

If you haven't tried a bristle disc, see if a buddy has one to try out. I think you'll be pleasantly surprised. If it starts fanning out, it's spinning too fast. Just takes light pressure, bassically about the weight of the tool.

 

[JHZR2]

Now for timing cover, oil pan, valve cover, intake, exhaust gasket surfaces, etc goes exponentially faster. It also gives a very light cross-hatch surface that allows sealants to seal really well. Plus in many locations it's easier to get a 90 degree rotary tool in than a blade and scotch-brite. Hands get cramped quick too when wrenching for 8-10hrs a day doing multiple jobs while trying to manually scrub stuff.

If you haven't tried a bristle disc, see if a buddy has one to try out. I think you'll be pleasantly surprised. If it starts fanning out, it's spinning too fast. Just takes light pressure, bassically about the weight of the

I’m not sure I’d be asking the same question, and probably try much more by hand if it was an area that touched oiled areas. While I see no sign of abrasive dust with the bristle disc, even tearing apart a scotchbrite pad results in dust that I wouldn’t want inside the engine. Production conditions may be a bit different, but I thought that was a nono. Maybe if parts are removed and can be washed after that’s different?

 

[JHZR2]

Regarding the 120 vs 220 disc, I've never had an issue with the 120. Rule #1 with any forced movement abrasive is not sit in one spot or apply much pressure. I don't know how 3M quantifies their abrasive ratings on bristle discs? Because 120 sounds a lot more aggressive than the results appear during use. When I was a tech it was recommended that I use White (120) for aluminum, Yellow (80) for cast iron/steel and Green (50) was pretty much reserved for corrosion removal on non-sealing surfaces. Though I never knew or looked at the abrasive ratings, just going off what master techs taught me. One thing is for sure, those bristle discs are a game changer compared to the fiber backed scotch brite pad style discs since those clogged and wore so fast. Plus it was easier with those to creat high and low spots on a sealing surface since they are less forgiving to pressure applied.

As far as the pitting from the gasket, that's pretty normal and not much you can do about it. If you use an OEM metal layered gasket, you'll be fine.

Thanks. Yeah I’d be far more concerned about using pressure or holding it in place. Fortunately a slight glance of the disc on maybe half of the slowest speed range on my electric grinder worked perfect.

There’s no way I would have used one of those flat abrasive discs, sandpaper, etc., given the angles in play. But the bristle disc did work nicely just barely removing the stuck on junk.

 

[Cujet]

I am looking forward to the drive report. No leaks or rattling gudgeon pins... (just kidding, that is not what the noise was)

 

[JHZR2]

I am looking forward to the drive report. No leaks or rattling gudgeon pins... (just kidding, that is not what the noise was)

If only I had the time to get things done.

But I wouldn’t trade the family time for a million fancy NOS Mercedes diesels, of course.

 

[JHZR2]

I can’t say that a razor is a better tool. And it significantly increases the risk of gouging compared to the bristle disc.

It does get some dirt off though. Not much and not to bright metal. Though I’m not necessarily going for bright.

Here’s the issue du jour. since I have all threads chased, things as clean as practical, I’m looking at the manifold.

I knew there was a slight turbo gasket leak.

Here’s what it looks like on the manifold side:

So I spent some time to just work on the surfaces a bit. They still are somewhat porous.

Then I checked for flatness from both sides and across. There is about 0.010” irregularity across.

I’m not sure I want to have the manifold resurfaced, but I’m not sure when I’d condemn it. Would having such a surface imply that I should use some high temperature RTV or copper gasket covering to help with sealing? I’ll probably use one of those graphite coated 1/8” compressible turbo gaskets instead of the super thin stainless ones that came on the vehicle.

Thoughts??

 

[spasm3]

Is there a reason not to have a machine shop take a little off to resurface?

 

[JHZR2]

Is there a reason not to have a machine shop take a little off to resurface?

Time, money, not having one I know and trust…

Otherwise no. I’ve never done this before.

I actuallly do think it will be necessary. Look at the turbo flange:

When I put my straight edge there I see light. Feeler gauge says it’s 0.009”