1HDT Head Gasket Issues (1 Viewer)

[Wildnlost]

I noticed recently that my Land Cruiser with 1HDT was pushing a bit of coolant into the Overflow. I remove the head and did an inspection. I found cylinders 4 5 and 6 we're leaking on the right hand side of the Block near the back into the water jacket. I checked the cylinder head for straightness and it's flat and looks like it's probably been recently machined. I measured the block and found that there's .003" warp in the block deck. The service manual says .007" is the limit for warp. Mainly the right-hand rear of the block has the issue when measured with a Precision straight edge.

Also of note the head bolts seemed pretty loose in comparison to when I installed them. Before removing them I loosened off a few and retorqued them back to the factory spec. To my surprise all the bolts took 90 degrees extra turn at least or more to get back to factory torque spec. 51 ft/lbs + 90* +90*. Bolts oiled, cleaned the threads in block with tap. Oem gasket and bolts.

My questions are
.... is .003" too much warp for a motor pushing 25 psi?
..... did my head bolts stretch or did I not torque them properly when using the factory procedure.

 

[mudgudgeon]

I loosened off a few and retorqued them back to the factory spec.

I think this is probably not a good move.
I'm fairly certain the head bolts are "torque to yield". Every time they are torqued, they stretch which potentially weakens them.

Reusing head bolts is a little dubious at the best of times. I've reused head bolts on 1hd-t and 1hz engines twice now without any issue, but I would not reuse the same bolts a second time.
If the head has been off previously and head bolts reused, they are already stretched. Loosening and retorquing adds to this.

IF the head has been milled, carefully measure valve protrusion from the head and piston protrusion above the block deck before ordering a head gasket. The HD-T series engines are interference engines, ie, they rely on the gasket thickness to provide clearance between valves and pistons. Getting the right thickness gasket is critical, milling the head makes this more critical as valves are closer to the pistons after milling. There is fairly limited scope to mill the heads of these engines

I don't think .003" discrepancy in block flatness is likely to be a big issue, but happy to be corrected.

For the cost of new head bolts and new gasket, vs a total strip down to and rebuild of the engine to deck the block, I would change out head bolts and gasket, reinstall the head and see how you go, if that fails, then consider your options.

 

[roscoFJ73]

You need new bolts. Its a no no reusing them

 

[Wildnlost]

The bolts were new when assembled last time. Sorry for the confusion. My point is the the head bolts were not tight when I was dissassembling the engine to inspect the coolent issue. I re torqued the bolts to see how tight they would normally be when undoing the head. The head bolts were definitly loose comparing the way they untightened after retorque. The retorque was only for information to see what a standard torque feels like when loosened off.
What I noticed was the bolts turned another 90* to get to standard torque, Compared to the first assembly of the motor. 15k ago. I could see the old Sharpie mark on bolt. Both times I used an almost new Snapon torque wrench.

I question that they stretched. Is that possible with 25psi boost? Or is it a combination thing....a little warped....extra boost....now alittle leak. If I kept my boost levels below 15psi there was no coolant push.

 

[gerg]

I think it would be optimistic to think your motor made that kind of power. I'm not being sarcastic either, it's just not the most logical reason. There is a saying in healthcare. "When you hear horse hoofs, think horses...not zebras". When your head bolts need a retorque think torque scatter.

Many head gaskets ago I used ARP studs and meticulously cleaned my block threads and used the torque lube and, despite being reassured ARP studs don't require a retorque, I had to retorque them multiple times to get it to settle. Your 90degree turns were exactly what I experienced with my first retorque. I always use copper spray on the block and head now and also do a semi loosen and retorque after the first warm up/cool down cycle and recheck every month until it clicks on each one. After the first retorque I don't loosen again first. I try and let the threads settle where they want to be. No more head gasket issues for me. I hesitate to recommend retorquing fiber gaskets as I've crushed one so much my head contacted my liner before trying to get the torque to settle to spec. Was not happy with that at all. I'm not a fan of fiber gaskets....they compress....more and more and more. MLS is the way to go. I'd really only use a fiber if I had to do a dirty gasket replacement and need to get it to seal in bad conditions. I'm not saying you used a fiber gasket, I just hate fiber gaskets and wanted to get a dig in.

 

[mudgudgeon]

I question that they stretched

from my understanding of torquing a fastener to yeild, your extra 90° to re-torque being due to fastener stretch is plausible. But, I'm no expert.
It's the torqueing to yield that stretches the fastener, not your 25psi boost.
There's plenty of these engines being run week in excess of 25psi boost, if boost was the problem, there'd be more chatter about head gasket failure.

 

[gerg]

When you use rotational force to estimate clamp pressure everything that causes drag on the threads reduces the actual clamp force as you stop when you get to the recomended torque. You can't tell the drag from the clamp. It's a big guessing game. This is why this stuff has to be clean and free of burrs. This is also why many builders measure the length of the bolt to get the stretch instead of measuring rotational torque. It's a more accurate way to gauge the yield. It eliminates the middle man. I think they do this with studs on cylinder heads as they can measure how much the stud protrudes as the nut clamps down. Then you get the actual length of the bolt. That's a stud mind you. Not sure how yould do it with a bolt.

 

[gerg]

Come to think of it, can't you measure the bolts to see if the lengths are longer than stock to see if they stretched? Once they yield they don't return to the origional length. It's like going full retard.....

 

[OGBeno]

Come to think of it, can't you measure the bols to see if the lengths are longer than stock to see if they stretched? Once they yield they don't return to the origional length. It's like going full retard.....

Correct. From the 1HD-T manual:

 

[mudgudgeon]

Come to think of it, can't you measure the bolts to see if the lengths are longer than stock to see if they stretched? Once they yield they don't return to the origional length. It's like going full retard.....

Hence why loosening and retorquing nets another 90° rotation.

You'd need an accurate measurement of the bolts prior to initial install

 

[gerg]

The bolts and studs I use aren't tty. If he measures his bolts and some are stretched and some aren't it might shed some light on if they all yielded or not. If some did and some didn't then it might explain the failure.

 

[Wildnlost]

Come to think of it, can't you measure the bolts to see if the lengths are longer than stock to see if they stretched? Once they yield they don't return to the origional length. It's like going full retard.....

Thanks for all the input everybody.
Another puzzle piece to consider is the used MLS OEM gasket. Measures .051" thick and a new one measures .063". The gasket crushed .012". Did that happen day one when torqued or did it take 5000km to get that much crush. Thus the loose bolts. Or a little strech and a little crush.
You were saying you retorque after some heat cycles. ARP has some good guidelines and info in there cataloge regarding fastener engineering and testing.
I am going to recheck everything and consider my options.

So because it is not excess power blowing the gasket I decided to do a little more port work. I unshouded the valves.....idea stolen from Riverina Cylinder Heads facebook page. Didnt have the proper tools but made do. Not perfect but functional.

Kiera says happy Halloween. (funny she doesnt look happy)

 

[gerg]

Be careful deshrouding the intake valve as you can make it easier for intake reversion on the last bit of the intake valve opening when the piston is on its way up. This is especially true with low intake port velocities and longer duration. Both occur at low rpm which is a primary goal for most diesel guys.

 

[mudgudgeon]

Another puzzle piece to consider is the used MLS OEM gasket. Measures .051" thick and a new one measures .063". The gasket crushed .012".

Is that comparing like to like?
Toyota use one of five different thickness head gaskets in the factory, aftermarket there's usually 3 thickness available.

 

[Wildnlost]

Is that comparing like to like?
Toyota use one of five different thickness head gaskets in the factory, aftermarket there's usually 3 thickness available.

Yes both gaskets were 5 notch the thickness of installed gasket is close to the manual.
I was looking at head bolts from different vendors and I found these bolts with a different initial torque. 69ft/lb plus 90* plus 90*.
More things to ponder.
I have to think I cocked up the install even with the help of an experienced diesel tech at my side.
Cheers all.

 

[Wildnlost]

You guys in Austrailia have a lot of choices for top shelf engine builders. Lurking about on the web and found this too. Arp studs, oversize valves, lack of cash....

 

[Wildnlost]

Be careful deshrouding the intake valve as you can make it easier for intake reversion on the last bit of the intake valve opening when the piston is on its way up. This is especially true with low intake port velocities and longer duration. Both occur at low rpm which is a primary goal for most diesel guys.

I did think a little about this...
My thoughts....I think the 1HDT is tuned towards low speed running with little valve overlap and consevative valve timing for intake closing. I am sure I saw a published figure in a manual for valve timing. I would guess less than 25* after BDC for intake close which is very little piston travel. If there is reversion with stock ports then it makes sense that porting would increase the amount of reversion. I am interested in improving inlet flow into the cylinder and exhaust gases out...bulk flow.
The deshrouding will give a significant flow benefit when the intake valve is just opening.... the sooner you can get the gases moving the cylinder filling will be that much better. Gases are heavy and it takes time to get the flow moving or stopping. the deshrouding of the exhaust will have the same benefit for gases leaving the cylinder...start flow early in the valve lift cycle. this should provide more cfm of flow total.

in theory.....
wish I could test.....i'll need a pressure transducer in the intake hooked to an oscilloscope.

 

[gerg]

That's the problem with head porting. You can't measure power improvement easily even with a flow bench. I know when I port my heads I am continuously tempted to deshroud the intake valve....like constantly. I chose to work in the bowl and blend the grinds on the intake valve to improve flow up until it entered the cylinder. Deshrouding the exhaust valve is a no brainer. I based my porting off of low lift low rpm v8 engines that were focusing on building low end power. It's the only porting on an engine I've found that came close to running like a diesel.