What causes a valve to "burn"?

[erikv11]

Time to get rid of the Rudolph-70!!!

[jblackburn]

Never!!!

[mlanctot]

2001 V70XC- 239,000 miles #3 cylinder 60 psi....Time to rebuild the head.

[rspi]

I guess it's a case of old rubber. Maybe 15 years is all it'll take. There may be something to the "high mileage" oil additives. Hopefully it can help extend the life of the seals. Most of the car that I have seen go over 400k were cars that did it within 10 - 12 years. Seals still not aged to 15 years.

In the mean time, I will do my best to keep my injectors clean with the Lucas.

Thanks for everyone's inpug.

[parkbro]

1996 850 (non-turbo) bought in 2006 with 120K one owner Volvo Maintained. I continued all maintenance and ran 87 octane, unless I was planning a vacation trip to the NC Mountains then I'd fillup and use High-Test through-out the trip. While on vacation last June I was 'hammering up' the ole Mountain at 65-70 mph, CEL appears, had a low idle miss. I dropped off at local Volvo Dealer for diagnosis. Verdict= no compression in cyl. 5, ruled Burned Valve. I had towed home and in the garage it sits. It has 172,000 miles on it. I was puzzled, why did my 'built to last' and 'maintained to schedule' volvo burn a valve? My mechanic said, like anything else, wear and tear, the valves would only hold up so long. Another mechanic questioned if the fuel became lean on that particular cylinder? Either way I have debated on whether to get a rebuilt head from Clearwater Heads and replace it myself.
Nice Car, drives excellent, newly reuphostered seat, new tires, trans maintained and shifts strong, everything works well. Before replacing the head I was going to take compression readings across the other (4) cyl., could someone tell me where the compression readings should be on an engine w/ 172K miles? If they are within range I will probably replace head. The other thing is the fuel injectors and whether they could stand to be cleaned as part of my overhaul. I believe they can be cleaned via a Sonic Cleaning System???? Not sure of the term used when they 'bench clean' fuel injectors. I would do this to rule out the fuel delivery possibly causing the burned valve. The other concern I have and would like your input. I have put about 150 to 200 miles on this car since this occured, could I have damaged the catalytic converter in that few of miles. Your input on these (3) questions and any suggestions would be appreciated. BTW I love this car, it handles like no other car I've owned.

[rspi]

Still like that 16 year old car huh? Cool.

The compression should be 189 - 219, miles doesn't matter. You should check it with the engine warm.

I would guess that the catty is fine.

Do you ever run injector cleaner in the fuel? Not sure if the injectors need to be serviced at a specialty shop or not. May not be a bad idea.

[parkbro]

Never ran any type of injector cleaners, always used a quality brand fuel and trusted their additive would suffice.
On performing the compression test, a warm engine most definately, and I plan to remove the coil wire and the fuse from the fuel pump. Another question, and I believe I read somewhere earlier, that the compression test should be performed with the thottle body completely opened( full throttle) what is your understanding?

[erikv11]

Yes, fully open the throttle for the compression test.

To run the car on 4 cylinders is fine if you unplug the injector on the bad cylinder, spare the cat any further insults from unburnt fuel. 100 miles shouldn't be a problem but TBH I'm guessing ...

You are wise to get the injectors flow tested and cleaned, why not if you are spending so much on a top end job. For burned valves it is usually just bad valve stem seals, but running lean can be the cause. There are many vendors online I am sure several are good, this one anyway I can vouch for good work and customer service when I used them a couple years ago: http://www.cruzinperformance.com/fuelinj.html

[parkbro]

Thank you for your response. I am curious about the abbreviation TBH ?

[erikv11]

To Be Honest

But don't get me wrong, I'm always honest!