Valve stem seals? 
Bore skope and mirror sounds good; then look at the open valve and check for residue. No air pump holes, but sud should be there. One thread a few weeks ago showed valve stems full of oil residue, Iām thinking the exhaust valve stems donāt seal perfectly and the startup smoke might as well come from there - and why not tge oil consumption. Just useless guessing I think because this is the point where only having a look can tell anything.
I can live with the oil consumption as long as nothing breaks because of it. And no smoke, so Iām happy.
1 Like
Perhaps you could try a āhigh milerā oil? Paul
I use 20W50, and had Castrol in there at some point. Looking at pricing I donāt know if it would be worth it, Iād rather refill more often and change the oil regularly. I could if you or anyone has definitive positive experiences that make me want it. Do the high miler oils have any special properties (besides being thick I guess)?
My experience is a long time ago and amounts to āadditional thicknessā as you indicate. It did help with oil consumption - it was a product called BP Corse - now defunct. Might be worth doing some reading - expect there is a bit more technology now. Surely better than STP Oil Treatment or similar! Regards, Paul
**
Which means that that the problem is fairly benign, Davidā¦sort ofā¦
The quandary with oil āconsumptionā is weighing the cost of oil replenishment against cost of remedial action. To weigh this properly some effort should be made to clarify the cause. Mainly to asses first if the engine is consuming the oil, which has sometimes serious drawbacks - or if the engine is leaking externallyā¦
Place newspapers on the floor under the engine, idle or reving - or just let it stand. That will reveal external leaks - which may or may not be substantial or minor, and may or may not be easily remediedā¦
High oil consumption will cause soot/carbon build-up, which in the long run may cause problems. The spark plugs provides a crude indication - checked over time it may prove clues for individual cylinder faults. A āwetā compression test, compared to the ādryā test results will do the same - revealing bore/ring problems.
Generally; as the inlet valves are subjected to manifold vacuum - excessive valve guide clearances draws oil continuously from the valve cover areas. Valve guide wear carries its own dangers - though intact valve stem seals will mitigate oil flow from this source. The exhaust valves play no part in this, they are under pressure - however, being very hot, they burn oil collected on themā¦
Your stated oil āconsumptionā is far too high to be comfortable - and should not be too blithely ignoredā¦
As you are already running 20/50, and presumably with normal oil pressure; trying to fix this problem with āthickerā oil is counterproductive. Various oil additives are promoted to do this that and the other - however, using such additives without knowing the cause of the problem is likely to failā¦
And as an aside; if oil companies had some panacea - they would put it inā¦
frank
xj6 85 Sov Europe (U/NZ)
**
This is what makes it so weird: The plugs look nice, the cylinders donāt have an inch of carbon on them, there would be smoke. I donāt need to put newspaper under it to know it doesnāt leak much. As long as the exhaust valve stems are in contact with oil they can leak some which will then burn on the valve, and not show up anywhere but on the stem. After all it is a lot of oil to disappear.
Maybe there is some oil that gums up the rings so they form a perfect seal? If Paul thinks it helped then it might be worth a try. But not solving the problem weāre creating.
Iāll rather live with it until something develops. Then fix it properly.
David
Frank, what about some of the cleaning additives? We used to have Redex, which was like a decoke cleaner in a can and very effective on the heaps of my youth. Not familiar with the modern equivalents. Can anything like this assist with gummed rings etc?
I would throw some ATF down the spark plugs and let it sit for a few days .
Do it prior to an oil change so you donāt run with a diluted (slightly) sump.
I did this with the 3.4 that I am working on. It did help in that after a few days the level did not go down quite so much. I ended up pulling the engine as all the top rings were broken.
Many years ago my '87 Series III suddenly started eating a lot of oil. A quart every 400-500 miles.
Long story short I replaced the cylinder head with a rebuilt head from Coventry West. Oil consumption returned to the previous (and quite tolerable) 1 quart every 3000 miles.
I presume it was a valve seal and/or valve guide problem.
Cheers
DD
**
Indeed the Redex worked, Paul - but it was not an oil additiveā¦
My fathers Oldmobile was a case in point. It showed low compression on all eight, oil burning and difficult starting. Following the instruction we poured Redex into the engine in high idle. We smoked out the whole neighbourhood (really!), obviously burning out accumulated carbonā¦
Success? āYesā and ānoā - the engine now had no measurable compression at all. All compression that was, was provided by carbon build-up - the engine was simply worn outā¦
So I can endorse Redex for decoking purposes - but an āItalian tune-upā will likely do the same. Whether Redex may free stuck rings is in a different questionā¦
Frank
xj6 85 Sov Europe (UK/NZ)
**
Yes Frank, āadditiveā was the wrong term to use. I had a similar experience as a kid: my grandmotherās EK Holden was hopelessly coked from ānanna tripsā so my father tried Redex - smoke everywhere but no decoking to do - all clean on pulling the cylinder head. As I recall it could be used included with petrol - you could buy a shot at the bowser. Paul
Over here, that āsnake oilā was known as Casite. csrefully add through the carburetor to an engine at fast idle. Smoke up the neighborhood, oh yes.
We thought it worked???
For decoking,. use water. Much care needed, too much and it will lockuo the cylinders and stuff gets bent!!!
Older Chev sixes were kinown to smoke blue, but run just fine. A fix was a tin umbrella on the intakes, to shield the valve seal. One of my bosses had a 37 that was a beauty except for itās wacky front dubonnet suspension and the smoke. He ignored each. Well, as he was a service station operator, merely added oil. According to him, it wasnāt much.
but, his throttle foot was extremely light !!!
Carl
Almost qualifies as yesterday given how late it is:
I lost coolant due to a small pinhole leak in one of the frost plugs just where the starter is.
Got my intake manifold off with a small bottle jack. All of two minutes, but I wasnāt the first in the area. No hammer as @Paul_M_Novak suggested (I believe however that @MartinScherz had much more luck with the hammer method today), but his tips were very helpful - Thank you. Knowing itās possible is a big part of getting it done!
Whoever had been there before also used silicone on the gasket.
The leaking Welsch plug was what needed to be replaced. I was able to poke a small screwdriver through the rust.
Not as much crud as I expectedā¦ butā¦ no head stud either. Just a stump and nothing aboveā¦ Martin was kind enough to bring his borescope and we found something hexagonal. Conclusion, there has been an emergency repair long ago. Somewhat relieved!
I scrubbed the block and painted it flat black again, installed the plug with a thin coat of rtv and choice words due to the constrained space and replaced the wiring loom with the one from Martins engine so at least that part looks factory new.
The engine runs, but had an intake backfire (maybe due to all the brake cleaner still in the manifold and some fuel because someone forgot to plug in the distributor for the first starting attempt) and runs about well, but lumpy and sounds a little like it has an exhaust leak. Plenty of torque at too low RPM but I do suspect an intake leak caused by the backfire or even before. That and cleanup will have to get done tomorrow.
All in all it must have taken 9 hours. Here is a before, in between and close to finished picture.
Now that summer is here in the north I want this thread to pick up again, you can guess. I did make that trip to constance again, this time with less heat and only the headlights breaking (fixed forever with relays) and my mother has finally driven an XJ which used to be one of her favorite cars.
In the end Iām happy that I finally got the leak fixed and can now, hopefully, get through inspection.
The oil consumption is what it is and that might be the intake valve guides or the seal.
David
1 Like
**
Have you run a compression test, Dave - the missing stud may imply uneven head torqueā¦
Frank
xj6 85 Sov Europe (UK/NZ)
**
1 Like
A while ago, yes. The other one I know is broken and will be more of a problem. Iām on borrowed time.
It has nothing to do with the missing, I didnāt touch the head. I believe the intake manifold is tight; weāll see about that.
David
It drives very well and did not lose coolant; and I had forgotten to push the spark plug cable back on after checking for spark (the forgotten pickup wire that I found this way).
The intake backfire is still there, but only on failing startup, so I suspect itās doing something itās not supposed to. Iāll get the CSI working. Timing feels good.
**
Traditionally, intake backfire signifies lean running, Davidā¦
ā¦but obviously wrong ignition timing will do the same. Adding that a combination of weak sparking and fuel issues may cause the engine to diesel - or soot build-up may cause āwildā firing. As may shorting between plug leads.
Just to complicate mattersā¦
Frank
xj6 85 Sov Europe (UK/NZ)
**
have you check the cam timing in relation to the crank? My 86 would occationally back fire through the intake, after a lumpty lump lump idle; then Pop. The Series II did the same thing; but in that case it was the distributor that was the culprit. the bush / bronze bearings where so worn, that it would randomly fire when it wasnāt supposed to. One time It caught the air cleaner on fire. Never a dull moment with that car. Now it sits for two years now over in the garage at my ex-wifeās; waiting for me to finish the Series III to either sell, or give to my daughter. This one is till up in the air.
Iām sure there was a purpose to this. but it escapes me right now. 
1 Like