Stuck piston ring diagnostic help on H

[RufusTheDufus]

I've been having compression troubles with the H in my 1980 HJ45. When I got the truck it ran like crap. Did a compression check and leak down test which revealed loss of pressure on cylinder #4. Leak down showed the rings to be the likely culprit.

I did a couple of overnight Seafoam soaks and compression went up close to normal for a while on the problem cylinder at 350 PSI. All of the other cylinders are at 390 to 400 psi.

A few days ago I did a 250 mile round trip to Portland on this engine. 110 miles of it was on the freeway running around 3k RPM. (Tiny Tach.) The engine didn't like it. Now cylinder #4 is only holding 200 psi, not enough for combustion.

I pulled the head tonight. There's no telltale signs of head gasket problems. The valves on #4 look OK with a visual inspection. No burned seats or other obvious problems. The cylinder wall shows no signs of scoring or wear. (I can still see the cross hatch hone pattern on the cylinder walls.) There's a bunch of carbon built up on the cylinder walls above where the rings stop presumably from the cylinder not firing.

Is there any way for me to tell if I have ring problem without dropping the oil pan and popping the piston out of the engine? All of the other pistons have a slight amount of play at TDC. I can wiggle them slightly in the bores. #4 won't move like the others which makes me think there's a ring problem.

I soaked the piston and rings for a while with penetrating oil and then tapped it a bunch of times with a plastic mallet hoping it would free up a problem ring. It didn't help. It still won't wiggle in the bore like the other pistons.

Any suggestions?

Any suggestions?

 

[Tobugrynbak]

Looks like you've done all you can without delving deeper into the motor.

If there is a stuck ring it'll need to be sorted with the piston out. At least it can be done with the engine "inframe".

 

[bigbrowndog]

If you have gone this far just bite the bullet , drop the sump and fit new rings. The bore in the H and 2H motors are very hard and it will only need new rings if you continue to use it this way you will at least glaze or score the bore when the ring fails. The ring is most likely cracked through in 2 or 3 places. Goodluck.

 

[RufusTheDufus]

I'll drop the oil pan. I just don't have a gasket for it so I was hoping to avoid it if possible. I'll order another one from SOR along with a set of pre-cups. All of mine are cracked.

 

[hj herby]

When I pulled the head on my 12ht last year things did not look too bad ................but when the pistons came out ,well I have never seen rings like it ,broken ,stuck ,ring grooves worn to twice there normal width and the bores are worn into barrel shape wider in the middel than top and bottom.So when you have the piston out make shure you mesure the bores top middel and bottom or you could be wasting a set of new pistons and rings.

 

[Greg_B]

In addition, make sure the ring lands are within spec. No sense throwing new rings onto a piston that is not in spec.

 

[Hendrik]

...but when the pistons came out ,well I have never seen rings like it ,broken ,stuck ,ring grooves worn to twice there normal width...

Those OEM 12HT pistons are (apparently, so I've been told) not the best. The ring grooves are known to 'grow'. I bought a 12HT recently and it was recommended to change the pistons as a matter of course before fitting the engine. There are better aftermarket pistons available.

GBENTINK knows a thing ot two about these engines - check his thread 12HT performance build.

 

[RufusTheDufus]

I pulled all of the pistons today. The lower compression ring on #4 is stuck and the oil ring is filled with carbon. The upper compression ring has worn the ring land groove to about double the size that it should be. Only two pistons are within spec. Looks like there's a set of pistons and rings in my future. Anyone know a good place to get a complete set for the H?

I still need to check the cylinder bores to see if they have worn to the point that they will need a bore job. I'm hoping I can avoid that step if possible.

 

[RufusTheDufus]

Out of spec?

This is what I found for #4. I'm surprised the cylinder bore is in such good shape.

 

[RufusTheDufus]

Any suggestions on where I can get a set of pistons and rings for an H? SOR doesn't list them on the website. I've emailed Roodogs and submitted a parts request on Engine Australia's website.

 

[bigbrowndog]

Toyota H Forklift engine rebuild kit diesel:eBay Motors (item 190314427419 end time Jul-13-09 15:04:17 PDT)

This shows up on Yankee Ebay, might pay to ask where the kit comes from and who makes it.

 

[amaurer]

Great googly moogly!!!

What is it about H pistons that would cause this??

 

[hj herby]

all-american.nl in holland are very good they suplyed the pistons for my 12ht.Looks just like my 6 pistons the only real cause I think is old age!

 

[RufusTheDufus]

What is it about H pistons that would cause this??

The amazing thing is that the engine ran well after it warmed up.

I think some skate punk kid in Brisbane had the truck before me. (There was a bunch of skateboarding stickers on the interior walls.) It looks like it was run with a defective thermostat for a long time so the engine never got up to operating temp. I suspect poor oil change habits based on the amount of sludge in the engine.

I've been told that most of the aftermarket pistons for the H series engines have a steel insert in the top compression ring groove to alleviate this common problem. I don't think it's unique to the H. Apparently the 2H and 12HT pistons do the same thing. It must be the stock alloy that Toyota uses.

 

[bigbrowndog]

Cheers, these are a set of over sized pistons for a 2H with the steel insert that you have mentioned. pic is a bit shiny but you can see the insert at the bottom of the middle ring gland. These are Hypatec Pistons in the pic. If you take your piston in to an engineering shop so they can measure it up for dia and height also need the rod connection size and rod connection position location in the piston then they can get you a forged piston that will be better quality than the Toyota piston. cheers gazza

 

[RufusTheDufus]

I just spent an hour with a bore dial gauge measuring my cylinders. All but one are within standard spec. The one that's out of spec is only 0.005mm out of spec so I'm not going to worry about it.

I called the place in the eBay listing earlier today. They don't know anything about the parts they are selling. I asked a few questions and the only answer they could give is "The catalog says it's for a Toyota H series diesel." I'd stay away from them. They don't know anything about the parts they're selling.

I think I'll end up ordering a set of pistons from AU tonight.

 

[bigbrowndog]

Here a set of Hypatec pistons and rings for the H motor are AU $729.00 but they are only available as oversize 20 and 40 thou for the H. What ever you buy make sure they have the steel " Alfin Insert" in the north we call them turbo pistons [don't confuse with 12HT pistons,different again]. cheers gazza

 

[RufusTheDufus]

I've traded emails with three places in AU about a piston set for the H engine. All three say the same thing: there are no aftermarket pistons in the STD bore size for the H with the steel insert because there's never been a turbo version of the engine. I'd rather not have to bore the engine just to use the pistons with the steel insert.

 

[bigbrowndog]

I've traded emails with three places in AU about a piston set for the H engine. All three say the same thing: there are no aftermarket pistons in the STD bore size for the H with the steel insert because there's never been a turbo version of the engine. I'd rather not have to bore the engine just to use the pistons with the steel insert.

Yes mate, you missed the point we all know there was never a turbo version of the engine. quote,, In the north we call them turbo pistons... that is Oz slang or common useage for non technical version of "pistons with Steel Alfin inserts" Probably more correct would be local slang.
Further Precision Industries make a standard size in their "Hypatic Piston" that has the steel Alfin insert. As in the PM I said this single piston and a full set of rings is $660.00 here. Expensive as not many are made.

 

[bigbrowndog]

Remember when buying pistons that you get what you pay for ask what brand, where they are made and what construction are they. Like buying a set of Yankee ARP head bolts and saying the Chinese or Indian head bolts are as good.cheers