Burning Oil

After having had a main bearing knocking, I bought a second-hand 7M-GE engine. After all the expense of having it fitted, it too had a big-end knock!

So . . . I bit the bullet and found local engineers to fully-recon the engine. (They seem very reputable and have done a few 7M-GE's before. (Told them to torque the head down to 70 ft-lbs, as per advice on Supra websites) Ran it in, it's really sweet . . BUT . . using a lot of oil (about a gallon per 1,000 miles!)

They took it back in . . . seemed all OK . . although they replaced the piston rings to be sure, and obviously had to replace head gasket when re-assembling. But they have kept it . . because it is even worse! In fact it's even blowing smoke now. They are really at their wits end and don't know what to do. They think it must be the head gasket blowing . . . . but what can they do? (Head and block were obviously skimmed as part of the full re-con) . Should I suggest they fit an all-metal Head Gasket?

Further to my original message last night , I have just spoken to the Engineers . . . . . they have done a compression check and think the Head Gasket is fine.

They seem to think it's the PCV System that is sucking oil into the inlet manifold and therefore causing the oil consumption & subsequent smoke. They say there's lots of wet oil inside the Inlet Manifold where the PCV hose attaches. They were also asking me if there's some kind of valve inside there that might be faulty - it's hard to see, and my Haynes Workshop Manual doesn't refer to any kind of valve in the PCV system . . . .

However, I am aware (from this Manual) that there are lots of small differences to these 7M-GE engines between 86 and 93 . . . . . My original engine is late 1990 . . . . although the secondhand engine was either an automatic or an import, as the garage who did the original fit had to swap lots of bits over, including the distributor etc.

Any thoughts guys? Could the PCV system cause the burning oil . . . and what could be wrong to cause this?!!!

[GOGS]

hi
just a few ideas not just relevant to your specific motor but here goes;
1- previous turbine bearings + or previous faulty engine breathing bad, can both cause oil to fill up cooler +/or exhaust with oil.New motor/turbine does not cure all. <_<
2- exhaust baffles then ommit smoke when starts to heat up.
in some cases it just does not clear +can literaly fill the road with smoke h34r: .Only twice in last few yrs ive had to change exhausts to cure.
3- removal of intercooler +tip over will show if soaked in oil.If it is it will need flushed/replaced.
4- blocked /poor breathing can make oil in sump pressurize going all different routes it would not normally .
5- if its one cyl or so with a head prob then usualy itl show up with the plug fouling clearly with oil.ie intake valve throwing oil into intake enough to cause smoke must surely show at the plug <_<

[GOGS]

me again
also worth a note .
Remove oil + measure it cos ive seen dipstics not reading accurate + burning off exess level till its lower.
Just curious-why would a cylander comp test check a head for not sealing to an oil gallery?

[suprra_girl]

if the compression is fine, and its a ge, only things i can think of would be really bad valve stem seals, the smoke would be most apparent at inital start up, other than that cant really be much else.

Ang

thanks Ang from Supraforums

Many thanks for your advice guys . . . .

It's useful to note that if it was valve stem seals the smoke would be mainly on start-up . . . also the car had a complete new exhaust system when fitting the new engine.

The smoke has actually got worse (the garage says) since they took it apart and replaced all the piston rings, even though they found nothing actually wrong! I think they must have cracked one of the rings putting it back in.

The main problem is they have been trying to say there's nothing wrong with their work, it must be something external. They say oil is being sucked into the Inlet Manifold from the PCV system and that maybe there should be a PCV Valve that is missing - but I have now checked and these engines don't have one! I think the oil coming from the PCV is INDICATING the problem, not causing it!

As they put another new head-gasket in on re-assembly, I figure it MUST be a damaged ring causing the problem

[GOGS]

Hi there
when the smoke is bad + engine cold pull plugs out .one broken ring will show up as residue if its as bad as you say.One bad sealing guide will do the same,but on removing head to fit rings its near impossable to strip without noticing what ports are throwing out oil.Bad sealing rings should stick out a mile with head off .

I have almost paid for rings from an engine reconditioning co who reckoned
chrome rings in a chrome bore was fine .I refused to pay for them
Something like wrong parts,wrong set ring gap,faulty head ie guides exess play through machining or wear is always poss.I have had a head leak oil extremely bad into bore cos the head wasnt skimmed right.Fine grooves just does not seal-worse with a metal gasket.
If the garage does not find fault then try locate which cyl is good [no oil] +which is bad?+post back <_<

check egr valve , it could be sticking shut....

supra420 check egr valve , it could be sticking shut....


Roger UK maybe there should be a PCV Valve that is missing - but I have now checked and these engines don't have one!

The 7M-GE does have a PCV system, it just does not use a removeable valve like most cars. Instead it uses an orifice in the
throttle body assembly. It's the pipes coming up from each of the valve covers into the throttle body. You can clean it out, the
factory service manual says to squirt some solvent into the orifice in the throttle body and blow it out with low pressure air.
Besides replacing the throttle body and valve covers, I think that's about all you can do. :blink: :blink: :blink: