Lehman 120 Piston slap

That'll buff out...

Oh- without a doubt?


1983 Present 42 Sundeck
Twin Lehman 135's

That's the reason that the suggestion was made to pull the injectors and peep inside with a laparoscope, looking for stuff just like that. Look in number 6 first, that's the one that usually bakes.

Forkliftt: I will bet you dollars to donuts that engine had been overheated. That's the cause nine times out of ten when I see that kind of damage. The aluminum piston expands with temperature more than the cast iron block, and once the piston grows, it creates additional friction, which makes it grow more, which makes more friction until it siezes.

Naturally, one cylinder will go before the others, but the rest couldn't have been far behind.

An overheat this serious is normally due to lack of coolant. If the system is full, boiling coolant usually prevents damage this serious.

With respect to the old Lehman, I'd pull the head and have a look at all the cylinders. It'll only cost you a head gasket set and a morning, those engines are pretty simple and the head can be yanked without lifting the engine off the mounts. Personally, I question the whole story about a 0.005" undersize piston being installed. Normal piston-to-wall clearance is on the order of .002 or .003, so adding .005 to what it already had would not be something a professional should do. If there were a problem with piston-to-wall clearance, then it should have been addressed correctly, not Mickey-Moused with throwing an undersize piston in.

Once you have the head off, then you can check the piston-to-wall clearance with a feeler gauge. If this "put in a .005 under piston" story is true, you'll be able to get a .004 or .005 feeler gauge in between the piston and the wall, down to the top ring. It's not a great way of gauging piston fit, but it will tell you if there's truth to this story.

That oil analysis ain't great - high aluminum, copper and iron spells trouble to me.

GOOD LUCK!

JS

JS- I'd take you up on that bet- but only to get a shot at some of your dollars. Come to think of it- I really like donuts a LOT- think I better pass?️


1983 Present 42 Sundeck
Twin Lehman 135's

Update

First off I want to thank everyone for all the help. I pulled the head off and had galling in #6 cylinder. All the pistons were .020 over #6 was not .015 ? Now the fun begins. A frame engine up and on a engine stand in the small salon of my trawler. Pulled all six pistons out and 1 thru 5 looked good. Rod bearing looked new and crank journals look good. Number 6 piston was slapping when it was at the lowest point in the cylinder and the galling. Five sets of rings .020 over one new piston .030 and rings. Hire Dan with Engine Savers and he bores #6 .030 with a portable bore bar in the boat and hones all six cylinders. I put it back together and have 15 hours on it and it is running good. Will be re torquing the head bolts in the next few days.

Hopefully all the posts will help someone else out. Thanks, Mike

Great news!! Thanks for keeping us in the loop!


1983 Present 42 Sundeck
Twin Lehman 135's

Great you found the exact issue, and the repair sounds as economic and sensible as it can be. Good luck, happy confident cruising.

Good news and way to put a wrench at it!

Many smiles ahead.

Not to be odd man out, but what the heck.

It was mentioned a couple of times that #6 has a cooling issue on lehmans, but I didnt see anything to chase that as a potential issue. It would really bite to have to redo this repair too 6 months down the road.

Barnacles, I hear you and know I am taking a risk but I did all this for under two boat dollars. This includes new piston, six sets of rings, upper gasket set, exhaust elbow, temp sending switch, thermostat, expansion tank cap mod with over flow tank and labor for boring bar. From what I can gather the damage was heat related. My temp sending switch is located on the side of the expansion tank and during coolant loss it is useless. I put the new switch on a tee and moved it down on the block where coolant feeds the water heater. I pulled the freeze plug off by #6 and inspected coolant passage around cylinder wall, it looked fair but cleaned it up just to be safe. I inspected raw water supply and cleaned up heat exchanger, both were good. Trans and oil coolers are new. Engine temp is 180 under load @1700 RPM and 173-180 with gun @ sending unit on head. I plan to take an oil sample after 70+ hours.

Two heads are better than one and this is all my brain could muster up.

Based on my experience I think you have a very good chance of a successful repair. Hand honing is never as good as a hole honed by machine but it still works. If the block was clean inside the water passage around 6 then it should be just fine.

Hello Buster - Do you have any details about how you did this "A frame engine up and on a engine stand in the small salon of my trawler. "

I saw your post in response to my own thread about a bad #6 and just noticed your post here today. I'm stuck at how to go about getting the engine up and on an engine stand in my salon. I would love to hear how you did it. Ive already called engine savers I just need to figure out how to get the engine up. I also want to replace my engine mounts. Also did you do your own alignment after resetting the engine?

First remove cylinder head this will reduce weight and allow you to get block higher off the floor. Make sure you use a engine stand that can handle the weight and length of the block. Build a truss to support the floor I used 6 2x4 to help support the floor. You will have more weight on the floor than it was engineered for. I used 2 4x4 ten feet long with 1 foot 4x4 attached at the ends to lift the ten foot section 4 inches off the floor. The A frame will go on top of the ten foot 4x4. Now when you lift the block out you will have room to put the floor panels back down. You are welcome to use my A frame, hoist, engine stand and lifting plate for block. I live in Corona.

Remove transmission before removing block

IF I had an engine that suffered from an overheat , I think extra instrumentation would be in order.

There are devices that will alarm if the cooling sea water flow stops .

A temp sender in the sea water discharge line , before the exhaust , could show higher water temperature.

Remember over 140F the salt is coming out of sea water , slowly blocking any heat exchanger.

Slight hi-jack of the thread with a similar issue. I picked up a 40' Bluewater Trawler in December for next to nothing. Motor runs, but not being very tuned into the noises of the Lehman 120 I didn't notice "the knock." I did replace all the heat exchangers, oil lines, updated raw water pump and had the injectors serviced, ie. did the service items. Engine smokes and started noticing the knock from #1 (not 6). Exhaust manifold is discolored (heat) near #1 as well. If you hold the fuel cut and turn the engine over with the starter the click-clack can be heard coming from #1, so not a fuel problem. I've talked to American Diesel and a few others and the common recommendation is to pull the head, hone the cylinder and replace the piston. The success of this route of course depends on the condition of the cylinder wall. The depth of the bilge is such that I don't think I'll need to move the engine to get the pan off and undo the rod. My question: is there any benefit to going further? I could replace rod bearings, hone and re-ring the other cylinders. All of this is pretty cheap (parts) compared to the labor involved. I've rebuilt several automotive engines and transmissions so I'm not new to this.

Option #2 is to go for a full rebuild. I'm not excited about this primarily because of the size and weight of the engine. If I dismantle in the saloon, the block will fit out one of the sliding windows. I'd slide it on a platform, but would need to be lifted down from the gunwale. Anybody know how much that block weighs? Can 4 guys carry it around or is that a recipe for lost toes and broken bones?

We bought this boat to be a floating apartment, not a long distance cruiser. But no reason to not try and get it running okay, even if it's just to the pumpout and back.

For reference:

Engine hours unknown.

Oil pressure is 45 psi with straight 30 weight.

Compression:
1 - 380
2 - 390
3 - 415
4 - 450
5 - 425
6 - 410

I was told by Brian at AD that 50 psi difference was max allowable. This has me concerned about #2, it was next door to the bad/hot cylinder.

stinkpotter, welcome. We also own a BW40 here in Seattle. Ours has twin Lehmans but many are singles like yours. As far as I can tell they go up on a gantry and then out the back door using a forklift extension (this assumes she's on the hard) or in a marina with a dock capable of supporting a forklift.

You might try inspecting cyl #1 with an endoscope (cheap from amazon these days) through the injector opening to try and "see" what you're getting into before pulling the engine.

Also, if you haven't already join boatdiesel.com. Great info and resources on FL's on there.

Finally, while not specific to your engine issue, if you're interested there is a BW40 Rendevouz coming up in May in Kingston WA. We'll be there with four to five other BWs. More info here: https://www.facebook.com/groups/142706656367590/

I admin the BW40 FB group but am merely a participate in the Rendevouz. I'd be happy to get you in touch with the organizer if you're interested.

Hi Airstream. I did pick up an $18 scope from amazon, they're down to 5.5mm now which should fit in the injector hole. Will be the first task I guess.

Wow, thanks for the BW40 info! Ours "Ceres" is an aft cabin on the same hull, so quite a bit different than the Portuguese bridge versions I've seen pop up online. The only escape out the back is a ladder up through a hatch and onto the deck above the cabin. She was delivered to NH, used around Florida, the Caribbean and Georgia, brought around to San Francisco and eventually up to Seattle. A pile of drawings came with her as well as the first owner's notes on anchoring in Hurricane David (cat 5, 1978). Ceres is on L-dock in Shilshole. If it's just a piston swap, I'll try and have her ready for a trip to Kingston in May. If not, we have a sailboat in Edmonds we can take across and say hello. Just joined the FB group...

'm not on facebook. When is the rendezvous? Won't have boat there, but would like meet folks and see their boats.

tator

Looks like May 4-6 Kingston, WA

Tator, it's in Kingston in May. I'll PM you the info I have and the organizer's email address. Would be great to meet you in person.

As mentioned earlier in this thread, number 6 is the usual failure on a Lehman. Make sure you carefully burp the cooling jacket and get a temperature sensor on/near that cylinder. It even might have something to do with the incorrectly marked dipsticks from Lehman. It causes other problems. The only way to tell is if the oil is drained and the correct amount of oil as per the manual is added, then mark the dipstick. The engine was designed to run level, not tipped back like in a boat. It might also be that the rear cylinder has a longer fuel pipe and might run lean? Many theories and no conclusion but its still a good old clamcrusher.

I think you confused me.... it was bored .o20over and then the .015 piston was installed?

stinkpotter, based on the advice you have and the way you use the boat, inspecting # 1 & 2 and fixing them seems preferable to doing the whole engine. I note #6 has the 3rd lowest compression but it`s within the 50psi range.
As you`ll be draining the block whatever you do, give it a good flush.That might help preserve #6.

Stinkpotter:

As a long time owner of a diesel repair business, I'd say your best bet is to remove the head and inspect the cylinder walls. You'll learn ten times more than with a bore scope, and pulling the head off a Lehman (Ford) is easy. You say you've done automotive engine work and this is no more difficult. Then you'll know what you have.

Once you look 'er over well, you'll see what you've got. If the engine really has a piston slap, there's a fighting chance there's more wear on the cylinder than you can clean up with a hone, but let's not jump to conclusions before you check it out.

GOOD LUCK!

John S.

motion30 said:

I think you confused me.... it was bored .o20over and then the .015 piston was installed?

Click to expand...

Ive read people doing that several times because they didnt want to chase why #6 over heats, and the 0.15 piston allows for higher cylinder temp and piston expansion. The piston expansion is why it gets quiet on warm up, and should also tell you the knock you hear when cold is the piston being under sized and rattling around. So no loading or high revs till it warms up and gets quiet or youll defeat the purpose of the smaller piston.

A solution is to run coolant to the freeze plug that sits in the rear of the block. They also mod the cummins 6B's this way, my replacement has it.

Update 300+ hours on engine since bore and hone. Oil analysis all fields in normal range now. Most important modification for a Lehman is expansion tank recovery system http://americandieselcorp.com/lehman-80-120hp-new-owners/ Thanks everyone for all the support

RT Firefly said:

Greetings,
Given the regular mechanical racket a diesel makes how does one ever hear a knock or a slap? Or a thump or a miss for that matter...

Click to expand...

True dat!

Update on my project

I finally pulled the head and went after my piston slap problem. Both #1 and #2 were pretty well knackered with aluminum stuck to the tops of the cylinder walls. #1 had two compression rings frozen in their grooves, #2 had one frozen. I used a ridge reamer, not to ream but to gently scrape the aluminum off the cylinder walls so I could get the pistons out. I removed all the pistons/rods, honed, replaced two pistons and re-ringed the other 4. Had the head rebuilt and replaced rod bearings. Rod journals looked excellent. The engine starts right up with very little throttle and doesn't billow smoke like it had. We ran it in for three hours and followed that up with 20 hours of cruising. So far so good. I think I still hear some piston slap, I need to listen to someone else's engine for a reference. But at Least I know what the parts look like in there. I may keep an eye out for a core engine to do a short block rebuild on and have it at the ready.



One question: what rpm do you Lehman guys typically operate at? I've heard 1800 and I know 2500 is the out and out max. We do about 6 knots at 1700 with our single.