What causes a valve to "burn"?

Post by **E Showell** » 14 Mar 2021, 03:04

Being a member of the burned valve club myself, I'm starting to think that we ought to be recommending replacing valve stem seals as preventive maintenance around 175 K miles for the white blocks.

Post by **abscate** » 14 Mar 2021, 04:15

I haven’t figured out a way to borescope these and have a look at the part of the valve you need to see , short of taking off the exhaust manifold.

I have learned the next time I see valve stem seal smoke, I’ll pull the head and do the seals rather than wait fir the droppedvalve. That will also Letme do the job in Spring/ Fall rather than the dreaded Jan/ Feb

Post by **RickHaleParker** » 14 Mar 2021, 05:26

abscate wrote: ↑14 Mar 2021, 04:15 I haven’t figured out a way to borescope these and have a look at the part of the valve you need to see , short of taking off the exhaust manifold.

You can get mirror attachments for the Borescope. Lets you see sideways at different angles.

: Borescope_Mirrors.jpg (60.81 KiB) Viewed 853 times

Post by **wizechatmgr** » 14 Mar 2021, 17:28

If you try the old rope or air pressure method, you may be able to do the valve stem seals in the vehicle... I know I was able to do that successfully on an '85 Cabriolet.

Post by **seggs** » 06 Jun 2022, 07:35

I bought a 2004 XC70 with 78k mi in 2015. Had a burnt valve at 193k in 2021. During that 115k period I owned it, I ran primarily 87 octane. Valve seals were definitely becoming worn at time given the oil consumption was steadily increasing. Approx 1 qt every 2500 mi. It was also really cold when the failure happened…like -10F in case that has any impact.
I did the valve job myself, which, wasnt too horrible. Just take your time do your research. The process allowed me to also do valve seals, cam seals, timing belt, pcv system, hoses and a few other things easily while the head was off. In the end, my compression came back to almost factory specs and the power improvement was very noticeable. Drove it for another 27k before selling it so must have done something right. I relapped the valve seats and they were beautiful. Only the valve was damaged. I mention that because some have mentioned seat damage. Maybe that occurs if driven too long on a dead cylinder. In the end, a new head isn’t always required. I used all the original components except for the burnt valve and valve seals. One note, I highly recommend oem valve seals. They are stupid expensive, but I used (what we’re supposed to be equal) aftermarket seals, and some oil consumption returned by 15k.
My using 87 octane may have caused the problem, but these days, with the cost differential for premium, If you can get 200k before a valve job, It may not be a be bad choice from a financial perspective. Again, it was a pain in the butt, but for about $500 in parts, I got a very refreshed engine.

Post by **abscate** » 10 Jun 2023, 05:44

For Firefox

xanthefin · Post by **xanthefin** » 10 Jun 2023, 09:26

E Showell wrote: ↑14 Mar 2021, 03:04 Being a member of the burned valve club myself, I'm starting to think that we ought to be recommending replacing valve stem seals as preventive maintenance around 175 K miles for the white blocks.

Lets see if i get there before any my 10 valves burns. I hope i get time and money fit this summer for operation.

What causes a valve to "burn"?

Re: What causes a valve to "burn"?