Lehman 120 head retorque

Over in my Tach Adapter thread I pointed out that I may have a little oil seep around the head gasket too.

I have searched this forum and the web for guidance but have hit a stalemate of views.

While scrutinizing my engine for sources of oil leas...I may have a little oil around the head gasket but notice very little or none flowing down the sides of the engine.

My manuals say "don't" retorque the head...but AM recommends every 500 hrs...and I get conflicting info off the web.

Any definitive guidance source? Something about stretch bolts on the newer engines and if mine was a rebuild in 2009 (PO gave NO additional info or documentation on it and AM has no records of it) I'm worried about a blind retorque while cruising....is there any markings on the bolts?

I'm wondering if I can go another 250hrs till I get home and just pull the head, new gasket and new bolts?

Any thoughts please.

I'd call Bomac Marine Power Group and ask Greg. They rebuild lots of Ford Lehmans.

Bomac Marine- Ford Lehman Engines, Parts, Tanks, Phaser Generators and Service

Consider this.

Buy, borrow or rent a UV light. Shine it on your engine and see if your oil fluoresces. Some does, some doesn't. If not there are additives you can purchase to add to your oil.

Clean your engine very well with some simple green or the like, getting rid of all the residual oil. Then start it up and use the UV flashlight to check for the actual source of the oil leak(s).

I have a dual wavelength flashlight that has found many a leak on all sorts of equipment using this methodology.

Many of the leaks were not from where I originally thought it was from, and saved me from unnecessarily taking things apart.

Good advice. Dye tracer is a cheap and effective troubleshooting aid.

thanks guys....

If, like the later Perkins, you have stretch bolts, then re-torque (or should I say re-stretch) is not necessary. How to find out if you have the stretch bolts... I'm not sure. The Perkins bolts look entirely different in that they are actually bolts not studs.

Yesterday my ford Lehman 120 wouldn't stay lit. Been starting every time for two years. Filters have about 60 hours. Ideas?

Psneeld, check your lift pump first. As strange as it sounds, the oil leaks out of the gasket on the block and migrates upwards and looks like a head leak. Many are caught by this one. It has a really crappy fit on the block, needs a new gasket and a smear of Permatex.

I'd almost bet a beer on this one.

Xsbank said:

Psneeld, check your lift pump first. As strange as it sounds, the oil leaks out of the gasket on the block and migrates upwards and looks like a head leak. Many are caught by this one. It has a really crappy fit on the block, needs a new gasket and a smear of Permatex.

I'd almost bet a beer on this one.

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Seriously????...oil migrating up against gravity over a foot higher??? and not spraying up there??

I'd love to hear from anyone else that's ever seen that one...just goes against my experience.

My leak is out of an injector line seal and migrating down the head gasket line and dripping down the back of the motor....

thanks though...

Seriously. Clean up all the oil and put a paper towel or similar around the lift pump. I threatened to bet a beer on it and so you know I am serious. It's something to do with the way the engine vibrates. Check it out first, before you ridicule.

If it's dripping out of your injector seal, why do you think its a head gasket? Just tighten it up.

I have checked it out...back when I first posted I didn't notice the leak(s) from the injector pipes but as they got a little worse they became ore obvious.

I have tightened them but the seals must be going.

Plus absolutely dry around the lift pump.

Reaearched fuel pump oil leaks and none of the discussions mentioned oil "vibrating" anywhere but down into the pan...just having a hard time believing it will migrate up a block side (wicking not possible as there's nothing to wick up).

The real reason for the post was the uncertainty to retorque the head or not based on lots of confliction info....I certainly didn't want to do it in the middle of a long trip and wind up with major maintenance but I didn't want to ignore it and wind up with major maintenance on a long trip.

I can live with all kinds of oil leaks as long as they are in the right sorts and can be monitored.

OIL is cheap, FORGETABOUTIT, and enjoy your cruise.

FF said:

OIL is cheap, FORGETABOUTIT, and enjoy your cruise.

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Thanks...see you tomorrow!!!

I agree with FF....don't worry about a small nuisance leak. Place a piece of an oil diaper to absorb it.
I am also not a big fan of retorquing an old engine.

jleonard said:

I agree with FF....don't worry about a small nuisance leak. Place a piece of an oil diaper to absorb it.
I am also not a big fan of retorquing an old engine.

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Pretty much the people I trust on here all say about the same as what is my experience...don't retorque.

I just don't get the conflicting info people report from American Diesel...makes me really wonder.

The engine only has 1000 hrs if the engine is truly a rebuilt as the PO stated..and had some documentation for...sure looked new and he did give me everything from a spare flywheel to injection pump to oil coolers, etc..etc...they had to have come off his trade-in core. Though he did tell me it was a 135 and it's really a 120..no biggie..just another verification of how clueless POs can be.

My big leak was the tach adapter that I pulled and plated over...easy peezy...and if the other leaks all stay small...I was planning on some more major stuff this summer where I sit for 8 months and hope another Sandy doesn't shake me from my slip too early in the season.

So another week in Ft Piece then the 45 day crawl back to NJ...hope you guys wear out winters welcome up there soon so I can return to warm gentle breezes and azaleas blooming........

psneeld said:

he did give me everything from a spare flywheel to injection pump to oil coolers, etc..etc...they had to have come off his trade-in core. ....

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And all this time I thought you had a single engine boat...LOL

jleonard said:

And all this time I thought you had a single engine boat...LOL

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I do...I also have a nearly functional, single Lehman storage shed....

I've re-torqued one 120 Lehman to address a head gasket weep. Put torque wrench on and none moved. A bolt that has been in place for a long time will not move even if tension has degraded.

Next, I marked each bolt position, then one at a time took each out, cleaned bolt and hole threads, lubed, then installed and tightened to specified torque. The marks showed the new position was generally 45deg more rotation than as found. Gasket weep was cured.

I don't know the Ford well enough to recommend (or not recommend) a retorque. It is rare for diesels to have such a recommendation, and even more rare for it to be done.

Simply putting a torque wrench on it and going to spec torque will not do anything unless bolts are very loose. Bolt needs to be marked, loosened and retightened. Good idea to clean the threads too, as dirty or corroded threads will not convert torque (what is measured) to clamping force (what is wanted).

Ski in NC said:

I've re-torqued one 120 Lehman to address a head gasket weep. Put torque wrench on and none moved. A bolt that has been in place for a long time will not move even if tension has degraded.

Next, I marked each bolt position, then one at a time took each out, cleaned bolt and hole threads, lubed, then installed and tightened to specified torque. The marks showed the new position was generally 45deg more rotation than as found. Gasket weep was cured.

I don't know the Ford well enough to recommend (or not recommend) a retorque. It is rare for diesels to have such a recommendation, and even more rare for it to be done.

Simply putting a torque wrench on it and going to spec torque will not do anything unless bolts are very loose. Bolt needs to be marked, loosened and retightened. Good idea to clean the threads too, as dirty or corroded threads will not convert torque (what is measured) to clamping force (what is wanted).

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Good advice...similar to what others have advised...

Fortunately I don't think I have a weep from the head gasket and if I do it is really small at this point...so I'm just keeping an eye on things till summer when I can decide whether to just keep monitoring or pull the head and replace the gasket and bolts with new.

Later model Ford manuals state that re-torquing is not required or recommended with the new style head gasket.

As far as lubricating the threads of head bolts ... that is almost guaranteed to to start another anchor thread. Unless the manual says to lubricate, and says what kind of lubricant to use, the amount of bolt stretch obtained with a lubricated thread may be far in excess of what is obtained with a dry thread.

If you reused your old bolts, the reason you got another 45 degrees is because they have already stretched, perhaps beyond their elastic limit. I would not trust them, particularly after being lubed.

But, not knowing the bolt or the specific engine serial and type of head gasket, my concern is purely opinion ... informed opinion but in this particular forum that may not be good enough. Caveat torquer.

True, bolt torquing is a complicated topic. I've done some calculations when I was in industry, and what seems simple on the outset can blossom into complexity. No need to go into that here!!

A few more details: A bolt can be examined for stretch (yield) using a simple (yet crude) technique. Mesh the threads of subject bolt with a new bolt- if light is seen through the threads, there is yield. Since most bolts do not engage all their threads, the yield will be above the engaged threads. On that Lehman, the bolts showed no evidence of yield, so they were re-used.

Another trick I used was to measure valve lash before I started. After retorque, the valve lash was reduced significantly (don't remember how much) so that indicated the head was pulled down. Note that valve lash changes as a multiple of head movement, depending on rocker arm ratio.

Need to reinforce that valve lash does need to be checked after retorque, as lash does tighten up. Some manuals are not explicit in that.

Thread lube is super critical. Follow those instructions. If manual specs oil, use oil. If it specs moly lube, use it. But DON'T use moly if oil is spec'd!! If lube is not discussed in manual, I use engine oil. I don't remember what the Ford specs were.

Dry threads are near impossible to get in a head job. There will always be a trace of oil in the bolt hole unless heroic steps are taken to clean it out. It takes just a trace of lube to change the friction coefficient.

Thanks again..will keep it all in mind...pretty aware of the lubed/non lube torques but will have to look them up/call around I guess...

Correct about the "dryness" of anything but a boiled block..but I'm sure somewheres close is the best many of us do anyway.