The 18R-GTE reference manual ...

[o_man_ra23]

Ok, I am possibly clutching at straws before going on to a full on new forged bottom end. I would like to get this engine going again without spending big bucks.

So... symptoms. Fully rebuilt 18R-GTE with sleeved bores, pistons have had the ring grooves machined to suit normal rings, pistons are 18R-GUE 8.3:1 compression 0.5mm o/s. Compression is 145-90-90-160 (so 2 and 3 are almost half what they should be), Intake valve 1 is the only one with tight clearance, which would explain the 145 reading on 1, motor has about 300ish kms on it since rebuild. Turbo is a CT26 off a Gen2 3S-GTE with unknown wear (though the shaft felt ok by inexperienced standards, and it spools well without sending oil out the exhaust). PCV is sending out monsterous blowby, even while cranking with the ignition disconnected. For a day or so it was overboosting out to about 11 - 12psi (rough guess, could be more) and this is when it showed signs of blowby. Didn't appear to have overheated. I replaced the head gasket expecting it to be blown between 2 and 3, new head gasket has about 20 seconds runtime now. Plenty of carbon in the combustion chamber due to running rich when no tune.

So it would seem to be the rings, but a wet compression test didn't change anything. So my next guess is that the rings are actually stuck in the ringlands. This would explain the uber low compression (just over half what cyl 4 has), the lack of wet test improvement (gap is too big for the oil to fill) and the monster blowby. Another possibility is broken rings. Same exhibited issues, not so easy to fix. Another possibility is fubar pistons. This will require a full new build, which will send the project into a nightmare of long term playing.

So, does this sound like a plausible diagnosis?? Are there options I have missed?? (the possibility of stuck/burned valves does not explain the uber blowby). If it is a simple case of stuck rings, has anyone tried the WD40 method of loosening them, and did it work?? There is currently a wad of WD in each of my cylinders being left overnight in the hope that I don't have to rip the damn motor out over christmas, get somebody competent to re-machine the ringlands, and install new rings - chrome this time.

What are my hopes of a happy christmas, and the avoidance of having to take the excel to Rocky on Saturday?? (I am confident in the engine if I can get the blowby sorted). I have just put new oil in with the new head gasket. The old oil was Penrite Running in oil, the new oil is Penrite HPR15

Help is appreciated. If you want to discuss this during the day, please email me on [email protected] (that email will be useless after Christmas)

[roadkill]

Hi

fwiw, just pull the bottom end apart and retest and measure it all. I remember my dad the other day saying something about pistons and bores not actually being perfectly round that there were apparently oval shaped (ever so slightly) so maybe you have round pistons and oval bore or vice-versa. Could it be a cracked block? It'd seems odd to me that it's two pistons and not just one. Is the blowby shooting the dipstick out of the hole or just evident throught teh pcv valve.

bEn

[o_man_ra23]

Because of the nature of the PCV, the crankcase can't build up pressure enough to blow out the dipstick normally... that would be a blocked PCV if it did that. I haven't tried blocking the PCV for long enough to shoot the dipstick either, but from the experimenting I have done, it looks like it would.

Pistons are normally made slightly oval as they expand further one way than the other due to the gudgeon pin. Bores are round though, as there is no way to ensure an oval hone.

Are there any oil galleries which run alongside the cylinders?? If not, then that makes it very difficult to assume a cracked block. Normally that is associated with coolant issues, which I don't have.

[JustenGT8]

Sounds like rings given the blow by....either stuck as you suggested and the fact you needed the ring lands machined to suit is a bit concerning, or broken from over boosting. If you had enough det to break the rings you would have heard/felt it.

I'd be inclined to drive it (as long as it's not pumping your oil out like mine did) and see if the rings eventually free up. Otherwise it's pull those pistons out for a full inspection

[river]

Hi,

I am wondering if there is a crack in the block between pistons 2 and 3. It would explain the loss of compression between those cylinders and also the blow-by - but dunno how you would get the block cracked there. Also, could be rings - but this would imply two pistons have ring issues, which is possible, but sounds improbable - or just bad luck.

seeyuzz
river

[roadkill]

Hi,

could to be something to do with having the bores re-sleeved?

bEn

[JustenGT8]

Hi,

could to be something to do with having the bores re-sleeved?

bEn

Not for blow by? Could have been a contributing issue for the BHG if the sleeves weren't seated but give the blowby it has to be rings or piston ring lands.

[roadkill]

Not for blow by? Could have been a contributing issue for the BHG if the sleeves weren't seated but give the blowby it has to be rings or piston ring lands.

hI,

Sorry, was more aiming at the fact that they may not be perfectly cylindrical. I'm guessing they were put into the block and the then bored out .5mm or whatever the os pistons were.

bEn

[The Witzl]

i'd do what Justen says.... then when that doesnt work, pull down the bottom end, throw out your block, get a new block, bore it out to suit the 0.5mm o/s pistons (dont sleeve it) and start again.

blowby is definitely rings.

[3jcelica]

Try running the engine in without the trubo running into the intake. My experience and others I know, is that running in with the turbo may lead to blow by due to not bedding in. Running it for 500k or so and see if the situtation improves. Can't make your situation much worse.

Roger

[timbosaurus]

have you run a leak down test on the four cylinders?

[o_man_ra23]

There is oily smoke pissing out the PCV, that was after an overnight bath with WD40. I am assuming the rings are either really stuck or fooked So this Christmas, I'll be pulling the engine down (hopefully the HG won't be stuck to the head yet), pulling the pistons out, and seeing what is doing down there.

So here's to a christmas of beers and blocks

[Omegaman]

when i had some piston ring issues, i pulled out the piston through the bottom end.
I undid the engine mounts and exhaust, raised the engine, dropped the sump and pulled the it out from there.
it's tricky, but doable.
Can beat undoing everything. Just a thought, to try.

[roadkill]

hI,

what's the odds though of getting the piston back in?

bEn

[Omegaman]

thats the tricky part. i managed to get it back in, the compression was fine after that.
though it hasn't hit the road yet.