Scored cylinder
 

I have an S70 with a scored #5 cylinder. All others are fine. Three years ago, I had a tune up on the car, never burned oil. During tune up, the tech broke a plug and it fell into the cylinder. He turned the engine by hand to remove the bits but was unsuccessful so he removed the head. In the process he discovered spark plug bits in the intake and exhaust valve so he removed both, lapped them and reassembled the engine.

it ran well to my estimation but at some point I noticed increased oil consumption. This took some time considering it was my wife’s car.

not knowing then valve work was done, I tried to reason where my oil consumption was coming from. Took it to a tech who figured it to be the turbo, replaced the turbo and PCV system. Still had oil consumption. Then the car started to miss badly and discovered a valve had burnt.

Rebuilt the head only to discover the scoring. We reassembled the head and the car runs ok but consumes a quart every thousand miles.

I’m concerned the engine will carbon up and burn another valve. Is there any way to hone a cylinder with out removing the engine like we used to do on old AMERICAN cars with rear wheel drive?

are you thinking the scoring came from a ceramic bit of spark plug or just wear and tear? How many miles on the car and how long do you want to keep it for? At this point it may be cheaper to drop in a replacement engine. BTW, a quart every 1000 is not what I'd call burning a lot of oil - and I wouldn't assume it will lead to a burnt valve in short order. I'd suspect that the burnt valve may be due to issues not resolved with the last head rebuild. With that said, If you go old school and want to try and hone with the block in the car, you'd need to remove the head, drop the pan, push the piston up and out, put some rags to keep the filings out of the bottom, hone with a proper tool then do a thorough clean up job and change the oil after about 500 miles. (done this on older american and euro cars). You will also want to measure the rings and replace if not to spec. With that said, if you have gone to the trouble of removing the head, how much extra work would it be to remove the short block and have a machine shop do the job? My sense would be to leave as is and live with adding oil ever 3rd tankful, and should it burn another valve consider a replacement engine.

Thanks. I wasn’t sure if you could access the crank given the 4WD and configuration of the bottom of the engine. The head was just done by a reputable shop who specializes in Swedish cars. I confronted the tech about the ceramic debris. He denies the cylinder was damaged when he assembled it so I’m assuming he’s being truthful. The head work done in the last month was first rate and that’s when we detected the scoring.

My theory was the engine started burning oil when the head was off the first time because the cylinder did get scored then but I can’t prove that. All I know is it started burning oil and three years later it burnt the exhaust valve in the effected cylinder. The car had 160000 miles on it when it burnt the valve and about 155000 when it had the spark plug issue three years ago. We’re at 184000 and I hoped to run it 4 more years. I have run every car I’ve owned 300,000 miles /15-20 years without any problems other than routine maintenance. Mobile one in every car and change it regularly.

maybe I’ll just keep dumping some stuff in the tank to keep the Carbon residue from accumulating on the valves but the oil consumption gets tough on the CCV.

It is conceivable to hone the cylinder without pulling the engine. The oil pan will come out on the 1998-2000's. I don't know about later years. 5 cylinder volvos had selective pistons, so you could replace the piston as well and you might have some leeway on the exact diameter. FWIW.

Ok, update.

we changed the 90 degree gearbox due to a leak and the tech changed the oil. He put Castro, edge full synthetic. I’ve been running Mobil one.

my oil consumption has dropped 70%. Could a scraper ring have been frozen and come free following the oil change?

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As the engine age the Mobile 1 is bad news for the car. I've had headgasket problems when synthetic was becoming popular, at least for me in the mid 90's. Use to own a 98S70T5 till the rear main let go on a pull. Purchased with 230Kish miles and ran it for 2 years and found DINO and Synthetic had different rate of consumption even though the brands were fine. Last year I tried the Mobile again when Costco started selling the 0W-40 and at $10 off a case for 6 qt it was pretty cheap. The 08C30T5, 03S80T6, 03GS300 and 03Odyssey all complained, were less quiet and less peppy so I just considered it a flushing oil and took it out after a couple hundred miles.

Castrol and now the Edge is Volvo's official oil though Castrol has been Volvo's oil for many years so it should be much, much better than the Mobile.

Glad to know the Castro was good for your engine as I have some soon to be used on the 03S80T6. As for the scraper ring the only way to find out is to go back to Mobile on the next change.

Blessings,

BKM

Interesting. My experience with mobile 1 has been really good. I had an infinity that I put 300000 miles on and it never burned a drop of oil. Same with a volks GTI and Subaru Legacy wagon. I drove over 300000 miles on all those cars and never had an oil consumption problem.

must just be the Volvo engine. But anyway thanks for the input. I’m sure you’re correct. It has definitely improved.

if you are considering a move to Synthetic with a high mileage engine, look for the high mileage formulas. High mileage oils have seal softeners which help make the rubber compliant again. I used this with good results on my 850T when it crossed 200K miles. With that said, I'm not sure if its the change to synthetic which helped your engine curtail its consumption. I bet if you go back to a high mileage formula dino you're consumption wouldn't go up or would improve even further. Just make sure you are using the correct weight for your engine and local climate.

Well, mobile 1 is full synthetic. That’s what’s been running in this car since about 40,000 miles. It’s not until that last few years that oil consumption spiked. I thought it was the scoring but, the fact that it dropped with the change to 5-30 Castrol is what stumped me. Maybe it’s just the lighter cold weight that is marking the difference. I don’t know. I really didn’t think it would. We’ve had a real mild winter so far.

I think I’ll run this for a while and see what happens.

thanks.