WMesik

As subject line indicates, my fresh LQ4 "rebuild" is consuming coolant. A little detail on the build. It started as a totally stock 2005 LQ4 with 67K documented miles purchased specifically to rebuild and replace the tired 2004 LQ4 in our work truck. The tear down upon delivery showed no indicators of problems anywhere throughout the engine. Cross hatch was present in the bores yet.

Basic procedures were followed prior to assembly such as decking the block, surfaced heads, pressure check the 317 heads, polish crank, fresh hone on the bores... All new bearings, rings, lifters, lifter trays, TTY fasteners and gaskets throughout and MLS head gaskets installed with type facing the heads. ***Note*** this is a totally stock rebuild and 6qts of oil were primed into the engine prior to installation.

Fast forward to start up. Engine started up at the 1st turn of the key and would be considered a text book start up IMO. Everything appeared perfect as oil pressure was immediate and steady, temp started to slowly climb and exhaust was clean and lifter tick was gone in a matter of a minute or 2. Went through a complete heat cycle (start, warm to operating temperature, shut off to cool) without any DTC's.

Following start up after setting overnite it started right up and was belching white smoke. Total run time has been approximately 15-20 minutes.

Has anyone on this forum ran into anything similar to this? My only thought is the pressure test on the heads did not reveal any leaks when they were not torqued down. Having prepared the deck and head mating surfaces to avoid this scenario I am ruling out head gaskets. Are the 317 castings that fragile?

Am I missing something? Appreciate any input before I tear off the known good 317 castings from the original engine and freshen them to swap out.

1FastBrick

iTrader: (16)

Did you confirm it was actually consuming coolant? Or just condemning it based on the following statement?

"Following start up after setting overnite it started right up and was belching white smoke. Total run time has been approximately 15-20 minutes."

How do you know it was coolant issue?

WMesik

The definite smell of burning DexCool and thick cloud of white smoke is the reason to single it out as the source. A single heat cycle was not really enough to say with certainty it consumed it rather than required topping off.

Oil is clear and no signs of contamination.

Any thoughts let me know.

RockinWs6

If coolant got spilled into the exhaust while you were removing the engine it will take a bit to burn off, I've seen this happen before. I would pressure test the system, if it is leaking coolant into a cylinder you will find it easily.

WMesik

I will certainly be testing the cooling system and using a bore scope to investigate the issue before tearing it down.

Hearing mixed reports of the 317 casting durability made me think others may have had had a similar experience.

Nothing that more time and $$ won't fix!

1FastBrick

iTrader: (16)

The only time I have seen issues with the 317 is when they are overheated or in a hard wreck. Usually, when overheated, they crack between the intake seat and exhaust seat in the combustion chamber.

When there in a hard wreck, the bolts can shear and sometimes you get cracking in or around the bolt holes from the stress of the manifolds getting pushed on. We purchased a used LQ4 from a wrecked truck that was hit on 1 side and the coolant would literally leak out of the exhaust flange bolt hole. There were no exhaust manifolds and we did not see any other issues. It drove fine for a while then 1 day it started leaking at the bolt hole. I found a used set, had them cleaned up and swapped them out 1 day. No issue since.

I have seen whole sides of the heads where the flange mounts ripped off in extreme case.

WMesik

Fast brick, thanks for sharing that. Even though the heads on our donor LQ4 did not see any impact damage, the engine was test ran prior to shipping and who knows how long it ran without coolant. Still puzzled why the first heat cycle was all good and then problems set in. It will be awhile before time allows further investigating, I will update what was discovered when the facts are known.

1FastBrick

iTrader: (16)

Suprizingly they can run a while before over heating with no coolant. My self, I don't let them run over 5 minutes.

WMesik

Mystery solved on the white smoke. It was NOT coolant as initially "assumed".

The following is an outline of testing performed to locate the source.

Coolant system pressure tested OK, tested fuel pressure for a possible leaking injector or faulty regulator. Had 58psi with key ON and maintained presure for extended period of time with key OFF. Removed spark plugs and they were ALL oily. Did a compression test with a variance of 7psi from high to low (105-112).

Immediately placed truck onto chassis dyno and performed a series of simulated driving tests to monitor AFR. A near perfect AFR of 14.5-14.7 during all simulations. Noted heavy smoke under conditions requiring rpm over 2500 with a simulated load of 17.7HP to reflect actual driving load.

Removed vacuum line at the rear of the driver side valve cover (labeled PCV) and oil was dripping from the line. Capped vacuum port and verified near perfect AFR of 14.5-14.7 with additional simulated dyno testing. Exhaust cleared up and the smoke mystery was solved.

Addressing the oil scavenging now.

If nothing else, this thread may help someone else not fall into "ASSUMING" anything prior to quantified test results!

1FastBrick

iTrader: (16)

Good deal!!!

Thanks for following up with what you found as well as the test you performed to get your conclusion.