Head gasket replacement

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Oct 15, 2011
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Was an Albin/PSN 40
Been determined by several that I should pull the head for a gasket replacement.

Bubbles in coolant, steady rise in pressure in coolant system after warmed up, oil and/or carbon in coolant overflow bottle, and a few other minor guesses by mechanics.

No overheating or unusual issues. Block was rebuilt about 2900 hours ago. This tiny leak has probably been with me now for a couple years and at least 1200 hours....good oil sampling trend so no panic....just getting around to it now that a trusted mechanic thought if the engine made it home this summer, time to do it.

Pressure tested manifold as recommended by American Diesel...held 25 pounds for an hour.

Checked for threads describing procedure for head gasket replacement but coming up empty on procedure, did find a few on why it was necessary.

Might like to make this a sticky for guys like me that will do all the grunt work, even if hiring someone to come in at the reassembly/critical procedures parts.

Any tips or suggestions? If the thread gets a lot of specifics, will try and turn it into a sticky or condense it into one.

remove the old gasket carefully to look for failure points. Use a metal straightedge to check deck and head for flatness. clean and roughen surfaces with steel wool or emery cloth to remove glaze. Follow gasket makers direction regarding sealant. Some gaskets have a sealant coating.
Some makers recommend new bolts because the old ones have already been stretched.
I torque in steps first round at 80% of full spec. Consult engine handbook for advice on dry or wet torque.
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Follow makers bolt tightening pattern or if you can't get that spiral out from center.

Some recommend retorquing after a warm up. I have never bothered if stuff is in the way. If access is easy why not?.
In addition to Bayview's fine suggestions----

Changing a head gasket can be a tough job depending on ease of access. Suggest that you consider taking the head to an automotive machine shop to have it tested for flatness and machined if needed.

One other suggestion.... if you need to remove the injectors, be careful cranking the engine to blow them out after the clamps are removed. They come out with a great deal of force.
What I am loking for is Lehman disassembly.

Manifold first?

Rocker arm assembly? Tie together? Injectors? How to mark or label during disassembly....indexing of certain parts...

What gaskets, sealants and washers to order up front?

Head bolts loosened in reverse of tightening sequence or it doesnt matter....

Special tools...

Looking for more than the basics...

Head is going to machine shops for dye penetramt check for cracks and warpage.

Motor oil lube on torque per AD.

The gasket is the easy part...other than a trained eye for damage inspection. Looking beyond generic tips but thanks for any and all.
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The rocker arm assy should stay together by itself. Follow Ford manual exactly. I don't believe any "sealant" is required. (Do not use any sealant not specified by the head gasket mfg) Use new head bolts, coat bolt threads with oil (per manual) and retorqing after 50 or 100 hrs is a good idea on the 120. I would not clean mating surfaces with anything like sandpaper or emery cloth or anything that could shed abrasive particles into the engine. (I always only use a razor scraper) Check of head by a known competent machine shop is a good idea. (The manual warns against milling the head due to possible valve/piston contact) Make sure you keep pushrods numbered etc., so they go back into the same location and with the same side up. Use all new gaskets/sealing washers on the injectors.

Except for the weight of the head its a real straight forward job. Just make sure all mating surfaces are very clean before re-install.


I have a copy of the service manual for that engine if you're interested.
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For disassembly:

Drain coolant from block and manifold

Slacken rocker adjusters. Remove rocker shaft as a unit. Remove pushrods and sharpie mark location (I number them 1-12)

Remove fuel return rail and injection lines and fitting that pass through side of head. Remove injectors, sharpie their location 1-6

Remove intake/exhaust manifold and coolant head tank

The way I remove head bolts is to use torque sequence (roughly, start at center and work towards the ends), and loosen a bolt, then tighten it about half of final spec. When all are at half, then go back and take them all the way loose. This gradually and evenly relaxes the load, making exact sequence not too important.

Set up a-frame and rig head off. Initial lift usually needs a pry tool to break gasket bond. I like rigging them off so no chance to have it get out of control and bang around.

Once off, oil up cylinder walls to prevent rust. Vacuum any coolant out of cylinders. Keep a towel over block if not working.

There will be little brackets, hoses, etc to deal with, not discussed here. In general, you want head stripped of all removable stuff prior to machine shop, or you may not get them back!!

No manual at hand, going off memory.
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As usual...thanks Ski.....had a lot of that from your and others previous guidance

KCHACE is sending me a manual for reference hopefully.

I have a heavy equipment mechanic that should help with reassembly.

Hope it goes as well as the dampner plate and tranny project.

Others please add or verify what has been said, still hope to get enough to make it a sticky.
Just wondering, since the leak is so small, would it be worth just re-torquing the head bolts to see if it seals the head gasket.
It's a bit of a long shot, but if you have easy access to the head bolts without much stuffing around, it may be worth a try.
Once head is off are you considering magna fluxing the head? A cracked head has some of your symptoms too.
Once head is off are you considering magna fluxing the head? A cracked head has some of your symptoms too.

If this was my project, I would take your suggestion seriously. But many times, a decision is made based on availability. The only time I was exposed to or even heard of magna fluxing was many years ago on the second shift at General Dynamics where I worked nights while attending URI days pursuing my BSEE. That was many years ago.
Already did the Ski advanced retorque method....no help.

Will take to a machine shop...not sure who can magnaflux hete...may just see the issue with the head off...if not ...will just have to roll with the punch.
Once the head is off, have a good look at number 6 especially looking for signs of damage to the cylinder wall. Unless it is pristine, now might be the time to decide if you need to haul the lump out or drop it on its side and do a cylinder rebuild too. Lehmans have his achilles heel...all the best with the cylinder head, it should be strightforward. If it isn't, try Industrial Engines in Delta, BC for parts, the lovely Canadian dollar should take out the sting.
Head shop will have their favorite crack detection technique, be it magnaflux or dye penetrant test. Just ask them to check for cracks. And not all cracks are fatal. I have reassembled many engines that had cracks and no later ill effects. Depends on the cracks.

The biggest deal on reassembly is CLEAN CLEAN CLEAN. I have seen many engine put together where corrosion and old gasket remnants remained on decks. Or bolt holes with crap in them. You want the decks cleaned to grey metal. DO NOT use scotch brite or similar rotary abrasive pads. Those things shed abrasive grit and will go places you wish it would not. Cam follower pockets and cylinder bores. I clean with a sharp wood chisel. Get the angle and pressure right and it will clean to grey metal and not make scratches.

Bolt holes: Clean with rifle brush and wd40. Blow out with comp air. Wire wheel bolts. Replace any bolts with dodgy threads or signs of rust. Run each bolt into each hole and make sure it threads in smoothly to below its installed position.

Bolts: take two bolts and mesh the threads together and hold together in the light. If any light visible one or both bolts have gone past yield and have stretched. Replace any yielded bolts.

Sealant: Some gaskets say no sealant. I ignore that, especially if there was a history of leaks. A thin smear of permatex #2 can seal up micro flaws that you can not see. Thin layer around compression ring and around coolant ports. Other techs may poo-poo this, I do it anyway.

Bubbles in coolant can be a leak soooo small that the gasket may look perfect when you pop it apart. Look at it carefully anyway.
I have all the manuals in PDF let me know if you need something but can't do until Tuesday afternoon I am out on the hook right now ( Dan forth lol).
Good time to look at your exhaust riser/ wet elbow if you haven't in a while.
Good luck!

Heed skis advice regarding scotch brute pads. When my son worked for good year many years ago they banned then because they caused engine failures.
I was wondering what is the importance of this? Shouldn't all the rods be identical? Thanks

The same basic length (yes) but over the years they wear differently in the cups (ball and socket) ends so it pays to not mix them up,

The issue being if in the wrong hole it can cause premature wear when settling down again thus effecting the valve clearance in short order

Cheers Steve
General Head Gasket replacement Guide:

Step 1: Getting down to the head gasket can be an involved process. Always mark and index everything before removal. In this case, it was easier to remove the exhaust manifold, head and intake as a unit. A service manual is the first and most important tool in the toolbox.

Step 2: Check the head and block for flatness. A machined straight edge across the surface and feeler gauge will reveal all. The service manual will provide specifications. Blocks or heads out of specification must be sent out to the machine shop and be repaired. The machine shop will also be able to check for cracks.

Step 3: Prepare the surface. Never use anything that will remove metal. Be careful not to scratch the deck of the block or mounting surface of the head. While it may seem like a good idea to use a scrubber pad connected to a power tool, the surface irregularities created can cause sealing problems down the road.

Step 4: Chase the head bolt or stud holes with a tap or thread chaser to remove any crud and prepare the threads. Use compressed air to blow out any stragglers. Correct head bolt torque is of the utmost importance. Any interference can throw off the torque readings.

Step 5: Pre-fit the head gasket in the correct orientation. Never use sealant unless specifically required by the manufacturer. Head gaskets that require sealant will usually come so equipped. The service manual will outline sealant locations and requirements.

Step 6: Correct bolt tightening sequence and torque is key to proper head gasket sealing. Use new bolts if required. Coat head bolt threads with some engine oil before installing. Always follow tightening sequence and torque instructions to the last detail.

Cheers Steve
Yep, not really necessary to keep pushrods in order, but since they wear in to the tappet and rocker, best to keep them in order. Minimizes how much drift you will have in valve clearance settings. And so easy to do.
So far so good, about 3 hrs of misc running on engine, took most of the advice and it seems to have worked..

Will run it hard after thos weeks haul and bottom job.

During this winters dead time, I will try to make thos thread much more detailed.
My Lehman Head Gasket

This thread is very helpful. I have twin Lehman 120s and on my starboard engine, have continued white smoke at low to mid RPMs and black smoke at 2k and above. Found oil under my coolant cap after 6 hour trip (after cleaning cap before trip). I think this is symptomatic of a blown head gasket. Engine runs rough and had previously tested/serviced injectors (they were fine) and checked valve clearances.
Was wondering if anyone has the 120 (2715E) service manual in .PDF?
Funny thing though ..100 hours after my head job, the bubbles and oil returned to the coolant. No other symptoms, but I never run my engine above 1800rpms.

800 engine hours, 2 near round trips to Florida from Jersey and 6 perfect oil analysis later and the engine is still running fine.

Giving it one more chance this summer, having a trusted engine shop try another new head gasket.
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When did you last replace your coolant? If its holding pressure, that doesn’t sound like s gasket to me but the manual does say to retorque the heads at (500? 1000?) hours. Try that first?
Thanks for post. I replaced my coolant last year and retorqued my head bolts last month at the same time I pulled the injectors.(before cleaning the inside of the coolant cap and subsequently finding oil under the cap). The torque specs were all good (no movement at 105 LBS).

The injectors were tested by Seattle Injector Co. and they said there were all consistent and right at spec.
Have you talked to Brian at American Diesel? 804-435-3107 He is a guru on Lehmans.
Talked to Brian last month but not since finding oil under the coolant cap. Perhaps I should link up with him again.

Other symptoms... Starboard engine gets up to temp much faster than the port. Starboard settles at 195 deg....port settles at 180-85 F. Port runs quiet. Starboard runs rough at all RPMs, as if its not firing on all cylinders. I’m told that doing a compression test of the cylinders isn’t conclusive. Figured I’d pull the head off and take a look...already ordered and received a new head gasket.
When you removed the injectors did you remove all the small copper washers on the injectors tips ? Have one or two been overlooked and left behind in the injector hole and then the injectors replaced with new copper washers. ?
That's caused many a scratched head and rude words, and will lead to rough running.
Yeah, good call. I replaced all the crush washers, so no issue there.
So complete disclosure. This boat was previously owned by a 96 year old, 3 War Vet. He was a B-26 bomber pilot over Germany...and he was German born, so imagine the internal conflict! He flew well beyond the normal 30 missions required (65 missions total), shot down twice over enemy lines and fought his way back back both times to Allied-controlled terrority. Then he flew in Korean and Vietnam (more heroics which I won’t go into). You can’t make this stuff up for the Greatest Generation. He owned the boat since 1978, hailing out of Gig Harbor, WA. Two years ago, the marina called and said his boat was listing 25 deg at his covered moorage. Engine room was almost completely flooded with the starboard engine completely submerged, and the port engine halfway submerged. I’ve known him my whole life (via my grandparents) and am military myself...so obviously I offered to fix his boat for him at no cost with the goal to get him back out on the water for his next birthday. A friend of mine and I pickled the engines with diesel fuel, hauled out the boat, and started the work. Long story short, we rebuilt the boat and got it back to working/cruising condition, and got him back on the water 6 months later (mission accomplished!!!). Included in the restoration was multiple oil changes, replacing the oil coolers on both engines and cleaned the entire coolant system incl the heat exchangers. But I’ve always noticed that the starboard engine has always sounded much louder the port, especially at start up and at lower RPMs.
So as you can imagine, much could have gone wrong after bringing these engines back to life. Even though I pickled the engines and hang cranked the engine and vacuumed the top end in the attempt to displace all of the water from the engine, perhaps I did some damage when I eventually fired her back up. I will say, the heat exchanger paticularily on the starboard engine was half clogged before I used wooden dowels and an acid solution to clean it out...so I’ve always wondered if previously this engine was run at hot operating conditions. I’ve also replaced the impeller as part of the coolant system reburishment.
So in summary, I’ve cleaned the coolant system, replaced the coolant, replaced the impeller, cleaned the heat exchanger, replaced the thermostat, verified valve clearances, verified injectors. The Simms injecton system hasnt’ been messed with as far as I can tell so I haven’t bothered to check injection timing. Seems like a head gasket issue given that I’m finding oil under the coolant cap, rough running engine, continued white smoke under low RPMs and black smoke at 2K RPMs and above. But I defer to you forum members’ advice as I’m not an engineer!

PS the Port Engine has no issues.
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