Toyota 2LT - Excessive Blow By After Rebuild, Rings not Seating (1 Viewer)

Joined
Apr 27, 2021
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Hi all,

I have just put together a new 2LT engine (reconditioned block & crank, new head, valves, pistons etc) and I have some massive blow by. The engine ran well despite, but made it less than 500km before blowing out the rear main oil seal from the pressure. The block and head were each assembled at the engine shop so not a home job mistake. Leak down test confirmed there is pressure getting out of the combustion chamber and into the crank case. No pressure escapes into the cooling system, which is leading me to think the head gasket has done its job, and its the rings that have failed to seat.

We used standard Diesel engine oil, not any specific run in oil, but other than that I can't see where we would have gone wrong.

Has anyone got any tips on getting rings to seat properly in a new build. Willing to give anything a crack before having to tear it down and go again.

Cheers.
 
Joined
Apr 28, 2016
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Opotiki,Bay of Plenty New Zealand
My first thought was that even if you don't respect a run in / break in protocol - the engine should not build up that much crankcase pressure. Certainly it should not blow a main seal out of it's seat. Is the crankcase ventilation free ? With an open crancase ventilation it must have had a hell lot of blowby to blow the seal.
Something was not put together the right way down in the reconditioned block is what I am thinking.
 
Joined
Apr 27, 2021
Messages
2
Location
New Zealand
Hi all,

Sorry for the lack of reply, finally had a chance to remove the motor this weekend...

We found that the rear main seal was in fact, in tact, and the leak had come from the rubber sump seal which had split at the rear of the engine. We torqued the sump down far too hard which caused the rubber to fail. We could not tell if the rear main was actually leaking due to the amount of oil that had gone everywhere - we replaced it anyway to be safe. We also cleaned out the bores with carb cleaner while we had it on the stand.

We installed a boost gauge and found the turbo to be significantly over boosting. Factory from what I've read is 7 or 8ish psi, 10 psi max. This thing was running at over 16 psi. We turned it down to 7psi. Dumb mistake to say the least not checking a new turbo...

Initial start up we found, with the oil cap removed, there is still significant air movement. I noted that you are able to place your hand and block the hole without your hand being forced off, so pressure is seemingly low.. Oil cap back on and dipstick removed, there is some air exiting this hole although it is very faint, minimal pressure.

My friend has a 2LT, no issues. We did the same test on his truck and same thing, lots of air movement at the oil filler cap but you can just sit your hand on the hole and no pressure escapes.. His engine is old so not the greatest test of what a 2LT should run like, but was useful to be able to compare.

Is it possible these motors just move a lot of air around? Is what I have described at the oil filler normal to see in a Diesel?


To answer earlier questions:

How many km has it done? What was the break in procedure?
Prior to the sump seal failing, only about 500kms. The break in procedure advised by the shop was to crank with lube and no fuel until oil was observed at the cam journals, then 20 minutes at 2000rpm in the driveway. Then a good drive at varying speeds but not to thrash it. We followed those instructions.


Is the crankcase ventilation free?
Yes, standard ventilation. Breather from rocker cover to intake pre-turbo. When we pulled apart over the weekend we noted a reasonable amount of oil coating the intake from the breather. Intake is all stock standard.


I would be asking the shop. Sounds like the ring clearance and bore is not matching.
The pistons are 0.50mm oversized, so a good point. I will ask the shop to provide more detail here.


First check the breather. Even if an engine is breathing heavily it shouldn't pop a seal out! How does it start? That is always the giveaway for diesel engine compression.
Breather is not blocked, it is blowing a little bit of oil into the intake but from what I've read that's normal? Considering a catch can to eliminate that. Engine starts really well, pretty much instant from when you turn the key. Can blow a little puff out the back if its been shutdown without letting the turbo wind down but otherwise very healthy ignition.
 
Joined
Apr 28, 2016
Messages
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Location
Opotiki,Bay of Plenty New Zealand
Yes - it would be good to check the compression ratings.
Good chance that your only problem was the overtorqued sump gasket.
Get a workshop manual and a good quality torque wrench for low torque settings and be surprized how low the recommended torque on most applications actually is.
You described that there is no pressure building up when you close the filler hole - that´s normal and shows that your crankcase ventilation is working.
If you really want to check blowby you need to disconnect the crancase ventilation hose at the rocker cover and hold your thump for a second or two over the port, don`t check for too long as the pressure will build up quickly.
There is always blowby - and quite a bit too.
 

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