Head gasket sealer on John Deere 750

[pmsmechanic]

I considered the tap it back together idea and that would probably work but I’m not sure you’d ever get it as tight as it started. I wouldn’t want to go up an entire bolt size. If you could change the bolt from metric to imperial or opposite of what it currently is and get a bolt only slightly bigger I’d like that idea. I’m not sure I’d trust a helicoil with a head bolt. They make a C-Sert insert that’s heavier duty than a helicoil but I don’t think there’s enough meat in the block for that.

I'm not concerned about getting it as tight as it was originally if there's enough meat further down.I thought of just cleaning out the threads with a bottoming tap and inserting a stud instead of a head bolt. I'm thinking there's enough meat further down to hold the torque but I'm not sure. I had also thought about not brazing at all but was concerned about a coolant leak.

You could also go up a thread size like you suggest and then have a shop machine the shank of the bolt/stud down to original size. The more I think of it I would use a stud instead of a head bolt. At least you can get the threads down to the bottom of the hole.

 

[etpm]

If it was my block I would try to determine if the hole could be drilled deeper and then bottom tapped. There might be enough meat. I would also want to braze the crack. That is certainly something that could be done with the block in place and wouldn't be very expensive. But really, if there is enough meat in the block a hole drilled deeper and bottom tapped could provide plenty of thread engagement even without the block being brazed. Of course a stud and not a bolt would need to be used but that shouldn't be a problem. And also of course the torque specs need to be checked. 94 foot pounds seems excessive to me, but then I'm not a diesel mechanic.
Eric

 

[Mike1955]

I like where your going with this idea. I would make a few changes. I would just lightly tap the crack back together as much as I could and then lightly V it out and braze. I wouldn't go to a next larger bolt as the stretch characteristics won't be the same as the original bolts. Installing a heli coil or equivalent would let the op keep the original sized head bolt.

To the op. I wish I lived closer. You need a good experienced mechanic. I won't say I'm the cats meow but I would sure help you out.

How would a guy V the inside of a bolt hole. Just thinking out loud but with all the welding technology could it not be filled up, then retapped?

 

[pmsmechanic]

How would a guy V the inside of a bolt hole. Just thinking out loud but with all the welding technology could it not be filled up, then retapped?

I would just V the outside and leave the existing threads as intact as possible. I'm reasonably sure that the threads at the bottom of the hole are still intact. If you weld everything shut and start over, you've just made a lot of extra work without really improving the situation. That;s my thoughts.

 

[4570Man]

How would a guy V the inside of a bolt hole. Just thinking out loud but with all the welding technology could it not be filled up, then retapped?

I should start with my day job doesn’t involve welding but I wouldn’t do that. With the size and depth of that hole proper fusion of the weld would be basically impossible. The next issue would be re drilling the hole. If you had a mag drill it would probably help but drilling it centered and straight with a hand drill would be hard. The block really needs removed and put in a drill press for that. And you wouldn’t attempt cutting or welding the inside of the hole doing it the other way. You would cut the V to be close to as deep as the wall thickness so you get full penetration from the outside.

 

[bmaverick]

Some bad news !
I got a new torque wrench that was defective resulting in the over tightening of this bolt that cracked the block.

This is the end of the road for this machine. No more money can go into it. The bolt will hold the 94 pounds of torque required.

See photo...

Is there any hope?

You should of went by the Yanmar engine service manual.

It is very possible to save the block. Especially since the damage is on the very end. This is a positive for you.
You can do this just fine with the block on the tractor too. Just mask off the other areas.

How to repair a casted block bolt hole on the outside perimeter.

- On the outside wall of the block, grind each crack as far down as possible in a V or U shape some 3/16ths (4.8mm)

- Wire wheel clean 1/2-in (13mm) on each side of the new groves you just made.

- Drill small holes at the base of the crack to prevent the crack from going further.

- Clean the entire area. Not with oils nor water nor WD40.

- Due to the nature of this crack repair for size and the bolt hole, install an unthreaded stud into the bolt hole that will resist being welded. Some people use a hardwood dowel, do not use plastic. This will prevent weldment material not to fill the hole.

- Use a wire feed welder with .035 stainless steel wire and a tri-mix gas of Co2, Argon, and Helium.
(why use this method, this applies only localized heat on the casted block. you do not need to change the casted block hardness to become brittle.)

- As the 1st layer of weld is 1/2 cooled, wire brush over the top of the weld. Until fully cool.

- Apply the next layers until you have built up weld to the outside for each groove made and layered into the outside wall previously cleaned up to 1/2-in (13mm) each side.

- Pull out the wooden dowel. It may break, typical, but easy to use a pick to clean out the hole.

- Let this all cool overnight or over 6hrs.

- You can re-tap the hole slowly and carefully. Little each time and clean out each time as you go down.

- New head bolts and STI Helicoils are a must. You would need to size the hole for the insert.

Heli-Coil® Taps & Gages | STI Taps | Screw Threaded Insert Taps | STANLEY® Engineered Fastening

Heli-Coil® Taps & Gages | STI Taps | Screw Threaded Insert Taps | STANLEY® Engineered Fastening

www.stanleyengineeredfastening.com

For the Helicoils, use Loctite 2620 or in a pinch 262.
How to Install a Helicoil That Won’t Retract

Both the Deere and Yanmar Service Manuals mention how to bolt down the head in a stage by stage and sequence method. @rScotty can even comment on what sealants are possible and to use it SPARINGLY.
Others who have had perfect flatness with heads and blocks take their time in each stage for torquing. They will let the head sit awhile before the next stage, ensuring the stress gets properly relieved.

We've heard others who don't weld, followed this basic procedure mentioned above using JB Weld. Personally, I've not used the stuff to make any valid claims JB weld would work.

Let's save your Yanmar in JD green paint.

 

[Peter 315]

Yanmar 3T80J cylinder head torque specs?

I'm replacing the head gasket. Can anyone help me with these torque specs and rockers?

www.tractorbynet.com

 

[bmaverick]

Yanmar 3T80J cylinder head torque specs?

I'm replacing the head gasket. Can anyone help me with these torque specs and rockers?

www.tractorbynet.com

Time flies. LOL

JD750 . . .

 

[etpm]

It looks like the corner screw was indeed over tightened. By 4 times no less. I am surprised that the main cap screws have such a high torque, but then, like I said previously, I am not a diesel mechanic. As to welding, bmaverick's post is excellent. Stainless steel is often used to repair cast iron and I have done it myself, but only with stick and TIG, and only with pre-heating. When brazing the pre-heating is automatic. But bmaverick's post about using wire feed with tri-mix and stainless wire is certainly a good option, especially since it involves less heat. And if this process had already been used with success then it should be used. Anybody who is already using tri-mix for SS welding would surely know how to weld this block. The weld should be able to be done without removing the block. The OP can really help and save money by washing the hole out with brake cleaner and making very sure it is super clean and oil free. When I used to do weld repairs on equipment that showed up dirty I would tell the potential customer to either take it back and clean it or I would charge shop rate to clean it myself. When someone called about weld repairs I would tell them to make sure the part to be welded was very clean and oil free, otherwise they would be charged for cleaning. I did get some folks who would do a half assed cleaning job and I would tell them flat out to take their dirty stuff away and clean it properly or they could just pay me shop rate for cleaning up their mess.
Eric

 

[IH3444]

Be interested in a picture of the "Torque" wrench that was used. I have Sears Craftsman torque wrench.

 

[oneal hicks]

If it is only a sealer issue all you may need is a simple thin coat of grease on all mating surfaces and a proper torque of the head bolts? This is the Old school method that has worked for years. (We often over think issues)

 

[Page2]

Another good reason why it's not advisable to seek advice on a message board!

 

[Mike1955]

Another good reason why it's not advisable to seek advice on a message board!

I see a lot of good suggestions on here. There are some not so good. And I’m glad I have the knowledge to separate them The good on here far outweighs the bad so I’m staying. It’s always refreshing to learn something

 

[Williy]

I don't know it this was mentioned but anytime you pull
the head toss the old head bolts and replace with new. As
the head is not friendly to the head bolts!

willy

 

[5030]

I don't know it this was mentioned but anytime you pull
the head toss the old head bolts and replace with new. As
the head is not friendly to the head bolts!

willy

That is correct because when you torque the head bolts to spec, the 'stretch' a tad and need to be renewed.

 

[pmsmechanic]

There are many engines where the head bolts do not need to be replaced after a rebuild. Especially older north American engines, Any engine with torque to yield head bolts on the other hand do need to be replaced. They are a one time use only bolt. The service manual for your particular engine will have information on head bolt specs as to whether they can be reused or not.

 

[5030]

Exactly, but then again, new head bolts on any motor are a pretty cheap date.

 

[pmsmechanic]

Exactly, but then again, new head bolts on any motor are a pretty cheap date.

A C series Cummins that I replaced the head on was $16/bolt from the local CaseIH dealer. If I remember correctly there are 26 bolts. Not my definition of a cheap date! And you didn't have any choice either. They were torque to yield head bolts. I could very well have sourced them cheaper somewhere else but I didn't look.

 

[5030]

A C series Cummins that I replaced the head on was $16/bolt from the local CaseIH dealer. If I remember correctly there are 26 bolts. Not my definition of a cheap date! And you didn't have any choice either. They were torque to yield head bolts. I could very well have sourced them cheaper somewhere else but I didn't look.

I tend to buy my torque to yield capscrews from Fastenal or Motion Industries versus a dealer. OEM TTY capscrews tend to have a huge markup when sourced from a dealer. Some stuff is necessary from a dealer, some isn't.

I'm familiar with that engine as the dealer I work at part time the lead tech rebuilt one and I got the dirty job of repairing the muffler which had a stress failure in the case itself. Don't price a new muffler for it, you'll faint. I HT brazed it for the customer and Tigged the stress cracked mount bracket back on. Much, much less expensive than the replacement unit.

OEM parts today are insanely expensive. Some of it is justified but most isn't.

 

[Paul Campanis]

I am very grateful for all of you helping with my tractor. So many of you have been a tremendous blessing. I'm following up on all the advice / input and learning and growing in my mechanical skills. It has been like drinking out of a firehose but I am excited to learn so much. As a charity we do not have the money to hire people for tractor repairs. We have to fix what is broken ourselves. I am following up with all of the advice, buying tools, buying parts and making baby steps and believe that in the end we will have a great working tractor. Thank you for not getting frustrated with me this process. Thank you for sacrificing your time and being generous with your knowledge.