Testing for PO low oil/engine damage/additives

[LM]

A long-time friend just bought a 91 Saab 900 turbo, 110K mi, dino oil, manual trans. Rear engine seal leak noted, but initially not in magnitude. Leak volume variable, but on highway drive-back after purchase, 1 qt loss / 200 miles, while pulling (not-yet-replicated/verified) 29-35 MPG. Engine and turbo (boost needs adjusting) appear and sound okay - i.e., no noticeable smoke, plugs burning evenly (we'll be doing more exploration & tuning).

Tests for possible engine damage: UOA for high metals? UOA for additives ('stop leak' or similar)? dry and wet compression test? cylinder leak-down test?

Other recommended tests/suggestions?


Thank you,

Lance

p.s. - we plan to change out the current oil, hot, catching 2 -4 oz mid-stream for the UOA

 

[LM]

p.p.s. - 3/4 qt of Castrol GTX 10w30 was added at 175 mi on the driveback, necessarily, possibly skewing the UOA a bit

 

[Dick in Falls Church]

A qt in 200 is more than substantial.
In order to be of any value, you should have at least 1,000 miles of use on the oil--you can note on the information provided with the sample the number of added quarts and the lab will (at least should) make allowance for that.

You might want to run an Auto-Rx treatment. If it works, great. If not, you aren't out a whole lot.

Good luck.

 

[LM]

I've got a couple of bottles of Auto-Rx. Couldn't find it directly in the archives, but we'll likely use it (for the 1500 mi cleanse/2000 mi rinse) before replacing one or both of the crankshaft main seals, pending the below.

Rephrasing, trying to assess, as accurately as possible, whether the engine health is good, or damaged to some extent.

And whether an add was used.

Will the tests above reveal this?

Would this post be more appropriate on "Auto & Lubrication General Topics"?

 

[HardbodyLoyalist]

Can you run a compression test?

In the short-term, how about switching to a slightly heavier oil? An HDEO 15w40 perhaps? Might slow the leak a bit and will probably help the consumption, although it's not going to do the cat any favors.

 

[Drew99GT]

Many times oil will leak past worn out seals in the center bearing section of old turbochargers. Try taking off the lower intercooler pipe and see if there's oil in it. Look in the intercooler as well. I bet there's gonna be puddles. This oil also comes from the crankcase ventilation system so undo the inlet pipe into the turbocharger and see if oil is coming through the vent hose there. Also, if the center section gets coked up/oxidized oil, it won't get enough lubrication or the return line can get plugged with crud and oil will just keep spilling past the turbo seals filling the intercooler and not necessarily putting blue clouds out the tailpipe.

I'd look at the turbocharger 1st for the oil consumption, then MAJORLY gummed up piston rings, which Auto-RX will solve.

I'd put a new turbo on it if it was mine. You may think it's good but just wait till you see how much better a fresh one performs. I definetally wouldn't mess with the boost without installing a real boost guage and only use a real ball and spring manual boost controller to try and adjust it.

 

[LM]

Thanks for the replies. Update: WOT dry compression (3 avgs) cyl #1 - 148 psi; #2 - 115 psi; #3 - 137 psi; #4 - 147. Just did a wet on #2 only - 120 psi. Burnt valve? The valve guides/seals on these engines are reputedly strong, but ...? Haven't done the real easy one of start-up smoke. Will have a leak-down test done. Did pull an oil sample, but not sure if of much benefit - haven't sent it in yet.

500 mile old spark plugs: #2 had a 0.5mm X 1.0mm black carbon ribbon deposit on insulator - it flicked off. All plugs burning evenly, albeit perhaps a bit cool (running highway plugs). Appears engine running was running way rich from PO. May run some GM top engine cleaner or water after researching this board a bit.

The turbo does appear to be leaking. There is a burnt oil smell after hard runs (don't know for sure it's from turbo). Will try to post a pic link. Haven't checked/set base-boost yet - currently only boosting about 70% of spec.

The top of pistons - what are they called? - domes? - are all pock-marked. Can't get a pic with the digicam. Doesn't look normal vs others. Pre-detonation?

There is an smellable and audible exhaust leak (or valve 'chuff'?) at/around exhaust manifold, turbo, downpipe area.

Hopefully this might just be a head-pull? Any other suggestions most welcome

 

[LM]

p.s. - the bulk of the oil loss appears to be coming from both crankshaft mainseals.

 

[Drew99GT]

The exhaust smell could simply be a worn out turbo. I've seen many old turbos come off DSM vehicles (Lasers, Talons, Eclipses) that were so worn out in the exhaust housing that you could hold it up to light and see light coming through the casting of the housing near the center section

 

[HardbodyLoyalist]

An oil analysis is never a bad idea on a car of unknown maintenance history. No telling what might be revealed -- coolant leaks, excessive fuel dilution, dirt ingestion, etc. If nothing else, it establishes a baseline.

I would still run ARX before I went through the trouble of pulling a head, though. The low compression on #2 may just be a stuck ring, and ARX has been known to slow or stop seal leaks.

 

[LM]

Yes - will send in the oil.

If #2 a stuck ring (which would be great), wouldn't the wet comp test have bumped up quite a bit more?

 

[HardbodyLoyalist]

>If #2 a stuck ring (which would be great), wouldn't the wet comp test have bumped up quite a bit more?

You'd think so. But then, I'd also tend to think that a burnt valve would drop the compression way below 115 psi, too.

You may ultimately end up having to pull the head, anyway, but I'd still go the 5-minute $25 route before attempting the $300 lost weekend version.

Mostly, I hate pulling heads because it leads to a lot of "might as well" repairs---as in, if the head's coming off, I "might as well" replace the valve springs and stem seals. But it would be a waste if the head were cracked, so I "might as well" have it magnafluxed first. Boy, I'd hate to come this far and then reinstall a warped head---"might as well" have it decked. But hey, that's just a personality flaw of mine. I digress.

 

[LM]

Yes - the 115 psi seems to be a 'tweener', and maybe has multiple contributing factors.

Your list + (may as well roll in) a new timing chain, etc ....

 

[LM]

The bad news

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic&f=3&t=003643