Northern Lights Exhaust Manifold Gasket Replacement

[PNM]

While removing, testing and cleaning up my expansion tank and replacing the elbow, I found small imperfections (pitting, etc.) in the tank to head mating surface. The new, thin stainless steel gasket doesn't allow for much adaptation to imperfections in the surface.
Should I use a Permatex sealant on both sides of the stainless steel gasket?
Your wisdom is appreciated.

[thesaltytar]

It's hard to say without seeing the flange what constitutes "small" imperfections, so opinions may be across the board.

As long as the imperfection is encapsulated within the surface of the flange (i.e., doesn't extend from inside the sealing surface to outside the sealing surface) then the gasket should still be able to do its job, and in this case additional sealant would be redundant.

Also, what condition is the mating flange? You mentioned permatex on both sides of the flange. Also you mention having it apart.... Was any of this related to leaks? Or was the gasket holding?

People have a habit of applying excessive sealant or to over tighten fittings to stop leaks, sometimes this can make the situation worse (by warping aluminum housings from over torque for example) or just make a mess and impede future servicing.

If you still have doubts consider putting a dab of permatex on the flange imperfection, set the gasket on it and let the permatex cure for 15-30 minutes or so, then continue assembly. Another common failure of permatex application is assembling too soon before the gasket maker has a chance to take a light set and experience compressive force - applying and adding immediate torque will squeeze the permatex out of the flange and not enable it to provide the compressive sideways expansion that creates a better seal.

Edit: spelling.

[s/v Jedi]

Originally Posted by PNM

While removing, testing and cleaning up my expansion tank and replacing the elbow, I found small imperfections (pitting, etc.) in the tank to head mating surface. The new, thin stainless steel gasket doesn't allow for much adaptation to imperfections in the surface.
Should I use a Permatex sealant on both sides of the stainless steel gasket?
Your wisdom is appreciated.

I recommend you use a special gasket dressing. This does exactly what you need but it doesn’t cure so it’s easy to remove next time. Here is one from Permatex: https://www.permatex.com/products/ga...-sealant-2-oz/

[Ballsnall]

Originally Posted by PNM

Should I use a Permatex sealant on both sides of the stainless steel gasket?

I wouldn't hesitate it add a thin smear of sealant on assembly.

[skipperpete]

The OP doesn’t mention which model NL genset that he’s working on but if it’s one of the small ones (M673) the heat exchanger is also the exhaust manifold and the thermostat is usually under the front end of the exhaust manifold ....it does require sealant. ( some 673’s had it under the circulating pump)
More importantly, why is there pitting on the exhaust gasket sealing surface, this shouldn’t be exposed to corrosion and neither should the mixing elbow mating surface unless the mixer is leaking back into the manifold at shutdown.

[PNM]

The genset is a NL 753M.

The boat was on the hard for 8 years. The cast iron elbow rotted off. The edge of the head surface nearest the elbow suffered some pitting and the aft exhaust port on the head and manifold were nearly clogged with exhaust residue. One of the elbow flange studs twisted off during disassembly.

The old SS gasket showed some black spots on the aft side of cylinders # 4 and #3 where adjacent slight pitting could be seen on the head and manifold.

I removed, cleaned and tested the expansion tank/exhaust manifold, drilled out the elbow stud, and cleaned out the stud threads with an "M8 1.25" tap. I installed a new stud, SS elbow and SS gasket.

I used a very fine film of Permatex copper for high temp applications on both sides of the SS gasket.

Alas, when torqueing the manifold, I twisted off the top, center stud

I had the torque wrench set on 20# and it broke before getting the "expected torque wrench click". Maybe it was damaged at an earlier time.

So, I will order 3 new studs and 3 new head bolts, then I get to remove the whole thing and install the new manifold studs and bolts!!!

I might need a new SS gasket if I cannot clean the permatex off. In fact, I think I will just replace all of the rubber hoses and the belt at the same time. Might as well make this thing "like" new

Thanks for all of your wisdom. Any more comments will be appreciated.

Just a note! Its 90+ outside and the coolest place on the boat is in the engine compartment

[skipperpete]

Ok, the 753 has the thermostat under the circulating pump so no problem with that . Does this engine rotate? Put a wrench on the front pulley nut and see if she moves, after 8 years she might not. The blocked exhaust port doesn’t sound good. Get a vacuum cleaner and clean out all the crud from the port so none of it falls into the cylinder , if that valve happens to be open it will fall in as well as out. You’ll need a new water pump">raw water pump impeller and maybe a seal too.
And you really don’t need to use a torque wrench on manifold studs.

[PNM]

Thanks.

I replaced all of the engine and generator impellers during recommissioning.

I turned it over using a wrench, then it fired when I kicked it over with the starter, even with the fuel off, after I found the crud in the #4 exhaust port. So she is not stuck

I vacuumed the ports before and while cleaning them out with a wire brush, then a rat tail file to minimize risk of residue falling into the cylinder, but this is an imperfect process.

Good info on manifold studs. I should-a talked to you before twisting one off

Any chance I can drill that stud and back it out without removing the manifold? I suspect not, but I will try drilling the #6 stud with a 3/32" drill, then use a back-out tool to remove the stud. I will use a short piece of 1/4" OD steel pipe with a 1/8" ID to center the drill bit on the broken stud, so as not to damage the cast iron tank. I doubt it will work, but what the heck.

Hmm! This sounds more risky when I write it down. The tank is no longer manufactured and a used one costs $1500 if I can find one. Maybe I should just disassemble and then replace the stud.

Your wisdom is appreciated.

[Manateeman]

It’s a pain but have you considered taking it to a machine shop to get the stud out? It’s a fine generator worth saving.

[Rumrace]

Permatex all day everyday. You can re-anneal the gaskets in the over when the brides not looking

[Rumrace]

Stud out no worries. If it’s in cast aluminum don’t use release oil use drain cleaner diluted. The use a cobalt drill to make a centre point and use a bolt extractor to pull it out. Wash the drain cleaner off.
Cast iron block. Heat and bolt extractor

[PNM]

Question on drain cleaner? The head stud hole is about 4 inches from the surface of the expansion tank, where the stud is twisted off. Will any kind of release lubricant make its way through the expansion tank bolt hole to the head to help the removal process?

I can certainly squirt some lubricant in the expansion tank head bolt hole if you think it will make its way to the head.

Also, if I do not have to remove the expansion tank to replace the stud, will the cleaner damage the cast iron over time? I am not sure I can get all of the residue out of the 4" expansion tank hole before replacing the stud.

Thanks for your wisdom.

Have a good day.

[Ballsnall]

Get yourself a quality penetrant such as CRC screwloose and apply over several days if possible.
Centre punch the stud, then drill it out to just under the thread depth and remove with stud extractor. You can try the cheap stud extractors and if that doesn't work get yourself a quality set, they are well worth it as this won't be your last broken bolt.

[Rumrace]

Drain cleaner is a nasty alkaline easy to get ahold of.
Alkaline is used in aluminum cleaning polishing etching etc. It eats aluminum left on it. Got corrosion where aluminum and stainless are in contact drain cleaner 20% - rinse. Plug the tank with a rag

[PNM]

My NL block and manifold/expansion tank are cast iron. Ill try to get some penetrating lube through the bolt hole to the block, then accomplish the extraction.