Head gasket sealer on John Deere 750

[Paul Campanis]

A new head gasket leaked on my John Deere 750. Compression gases were coming into the cooling system after about 5 hours of use.

I bought a new head gasket from the John Deere dealer. What is the advisability of using head gasket sealer before installing it? If so what product would you recommend?

The engine manuel says not to use anything.

Should I have retorqued the head after a few hours of use?

Thank you

 

[IH3444]

You need to check and be sure that the top of the engine block is flat and not warped, as well as checking the cylinder head contacting flat which mates to the block for warpage. This is usually accomplished by using a piece of inexpensive ground flat stock and wrapping a piece of wet/dry 400-600 grit paper around bar and drawing it across both flats. Block and cylinder head. Notice if the wet/dry paper is contacting all surfaces. If not your block, or cylinder head is warped.
What torqueing pattern did you use for the cylinder head bolts? Cross pattern I hope. You also need to draw up the torque in increments. Some engines use stretch bolts. Does Deere ask you to use new bolts?
I torque up cylinder heads, allow to sit overnight, then retorque next day to allow for possible relaxing of components.

 

[Paul Campanis]

I have a proper straight edge and have checked both block and head for flatness.

There is nothing in the manual about replacing the bolts but I think that might be a good idea.

I'm certainly missing something. I'm also going to check and make sure the bolts are not bottoming out.

 

[IH3444]

The cylinder head may need to be pressure checked. Cracks sometimes are found between the valve seats and extend into the water jacket. The cylinder head gasket may not be your problem source, a cylinder head crack maybe. Some don't open up until engine warms up also.
Simple method is to glass bead cylinder head combustion areas and then visually inspect for cracks. A handheld magnifying glass can help also.
Money costing would involve taking to an engine machine shop for pressure check and magnafluxing of cylinder head.

 

[5030]

Sounds to me like either the deck (top of the block) or the head is warped or you have a crack in either and the only way to find out (if you cannot see it easily) is magnaflux them and I always replace head bolts with new ones because when you torque head bolts to spec, you actually stretch them.

What is the backstory on the engine? You overheat it or why are you replacing the head gasket, which is always replaced with no sealer of any kind.

 

[IH3444]

Straight edges sometimes don't show the whole story. Hence wet/dry 320 grit paper wrapped onto flat stock. This method with time and elbow grease can flatten out slight irregularities due to warpage.

Pardon Our Interruption

 

[5030]

Sounds to me like it's a bit more than a slight warpage. If it was me, I'd have the head and block inspected professionally by a shop competent in that work.

 

[pmsmechanic]

My rule of thumb is that every time a head comes off it should go to a machine shop and be planed flat again. It's very seldom that a used head is perfectly flat.

I've watched my buddy in his machine shop plane a head many times. I've never seen one clear up on the first cut.

 

[5030]

Do keep in mind that when surfacing a head (any head), removing material to flatten it. changes the base compression ratio and may or may not require a thicker head gasket or spacer plate to return the compression ratio to stock. Why head gaskets come in different thicknesses and/or have spacer plates available.

 

[D&D]

Again, you guys crack me up . This guy was encouraged by comments on TBN to tear down this engine without testing or experience and now he’s having issues and everyone acts like they have amnesia.
It is actually rather sad and happens quite often.

Cooling Issue

Greetings We are "I Was Hungry", a garden ministry serving the sick and the poor in Nashville TN, USA We use this tractor to till our garden plots but strange things are happening. When it is warming up antifreeze squirts out of the side of the overflow reservoir. This happened a while back...

www.tractorbynet.com

 

[ruffdog]

I'm certainly missing something. I'm also going to check and make sure the bolts are not bottoming out.

Bolts that go into a coolant cavity need sealer applied. Bolts can also "bottom out" on old sealer that is in the bottom of a blind hole. Those should carefully be cleaned out. What does the head/block mating surface look like? One other thread showed the surface that looked like a disk grinder was used. eek

 

[5030]

Sometimes a person needs to know their limits...

 

[Paul Campanis]

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?

 

[5030]

The price of scrap is pretty high currently.... Amazon imported cheap torque wrench I presume...

 

[LHF2019]

Or used wrong increments ft. lbs instead of in. lbs as an example. Guilty of that at work. Luckily nothing more than a turbo band I broke. Used ft. lbs instead of in. lbs. Wondered why it was taking so long to torque up, then it broke lol

 

[IH3444]

John Deere 750 Cylinder Block Casting Number 3416

Used Bare Block fits John Deere 750 750 3T80UJ CH18026 CH16658

Bare Block for John Deere Crawler Tractor(s) 750, Tractor(s) 750. Replaces John Deere OEM Number(s) 3T80UJ, CH18026, CH16658.

www.tractorpartsasap.com

 

[Williy]

I sure hope that you threw away the old head bolts
and replaced with new because you can't torque the
old head bolts to spec's

willy

 

[4570Man]

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?

That crack could likely be brazed up and the hole retapped for one size bigger bolt. That’s not the optimal solution but it’s really the only one short of a new block. I wouldn’t waste the time and money reassembling that without addressing the crack. It’s a little late now but the head needs to be surfaced before it’s reinstalled and the block needs to be checked for warping. The head bolts are one time use they need to be replaced. Also make sure the holes are free of fluid. Running a bolt into an oil filled hole can bust the casing. You also need check if the bolt calls for dry or oiled torque. There’s a big difference.

 

[pmsmechanic]

That crack could likely be brazed up and the hole retapped for one size bigger bolt. That’s not the optimal solution but it’s really the only one short of a new block. I wouldn’t waste the time and money reassembling that without addressing the crack. It’s a little late now but the head needs to be surfaced before it’s reinstalled and the block needs to be checked for warping. The head bolts are one time use they need to be replaced. Also make sure the holes are free of fluid. Running a bolt into an oil filled hole can bust the casing. You also need check if the bolt calls for dry or oiled torque. There’s a big difference.

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.

 

[4570Man]

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.

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 think you would have better luck holding a stud in the damaged hole vs a bolt.