Some of you know that I have become the "OCTANE" monitor and we all want to prevent problems. Of late, over the past 2 years, I have heard several people saying that a motor was bad because of a burnt valve.

A burnt valve is a valve, usually exhaust, that has overheat damage. This is usually caused because the valve is open longer than it should be. When a valve is open, it isn't being cooled by the block like it is when it's seated closed. When closed the heat is disipated and cools it down. So a valve that is stuck open or cracked open will heat up excessively and burn. The burn will cause the metal to deform and chip away or crack causing it to get even hotter because it's now a leaking exhaust valve. Sooner or later the damage is so severe that it no longer closes all the way and compression is lost.

Most of us know that these motors, especially the I5, was built to last 500,000 miles. So why are some of them dieing at 130k and 180k for burnt valves. From what I have found, it has mainly been the NA cars. Over the past week or so I have read numerous thread, articles, ask.com, posting about burnt valves and what people think causes them. The thing that stuck out most to me was information about ignition timing, the car running lean and exhaust leaks info.

I would like for people that learn of BURNT VALVES to post their conditions here if possible. My bet is that 75% of them are occuring in cars that run low octane fuel. The Volvo I5's and I6's run compression at 10.5:1 and do require 91+ octane. Sure they are made, through the knock sensor technology. to run on 87, however, that messes with the timing and may even cause the car to run a little lean. Running a car lean causes burnt valves. Sure it may take a while but if a car has burnt valves at 170,000 when it was built to last 500,000, you have really cut it's life short.

Other reasons for burnt valves include: a motor overheating, exhaust leaks, and plain old engine wear. However, I would like to know how many are running low octane fuel???

If you had a burn valve in your Volvo, please post your information here. What motor was in the car and what octane fuel did you use? How long did you have the car? If you got the car and 3 months later you learned that you had a burnt valve, you probably didn't cause it. However, if you owned the car for 8 years and was the one fueling it and servicing it, you would have a better grip on the underlying cause.

 

Great explanation...as you know i have the 960's I6...a really nice engine. I want to get at least 10 years out of this car...who knows where gas prices will be then..but in the interest of preservation and longevity i am gonna stick with the highest octane available...plus the gas I get is ethanol free...the I6 really loves that.

 

Is there a method to finding ethonol free gas?

 

Bam.

Ethanol-free gas stations in the U.S. and Canada

I tried non ethanol fuel one time, and the NA 850 did not like it. Maybe a couple tanks and the computer would have relearned the fuel trims, but I can't guarantee finding non-ethanol gas so I just left it at that. I always buy 93 though, I mean the cost difference is negligible. If fuel cost is that important to you, then go buy an old Fiesta or diesel Golf that gets 50 MPG.

 

I've posted this before...its what I've used ...HA! same link Turkey_Sandwich posted...

Ethanol-free gas stations in the U.S. and Canada

 

All of the ones in my city are unbranded stations. No shell, bp, exxon, etc. Does that matter?

 

No it it does not matter...try one tank and tell me you dont notice an immediate improvement in engine performance and throttle response...My gas station is unbranded but i happen to know the company is called Red Star or sumthing like that...there are some branded that do have ethanol free...just depends on your area. From what i see theres only one station that offers 93 octane..dont know if that location works for you...
I am fortunate that my station is 7 miles from my home and that it is in a direct line on my commute to and from work.

 

Just had an interesting discussion with my Volvo guy. When I asked him if he thought the I6 motor in the 960 was high compression and he said "not really"...and if it was necessary to run high octane gas all the time...He said it wasnt...but from it couldnt hurt to run thru a tank of premium now and then...

 

Very few people run high octane gas in their Volvo's. The cars run so well on the 87, people just don't give it a second thought. Most mechanics don't know these motors are running 10.5:1 compression, heck, they probably have no idea what any cars run for piston compression unless they have worked for a dealer and had formal training. The knock sensor system in these cars are great and do a good job, but that does't mean we should lean on that system when we don't have to. There may be a price to pay.

My Volvo guy that recently retired after 35 years of Volvo service said he never ran more than 87 octane in any of his cars. Claims it wouldn't hurt them.

 

After rough idling took my 07 XC70 with 240k km to dealer where a compression test revealed major compression lost in cylinder 4 (40 vs all others at 145). When pulling the head they discovered a burntvalve with a chip on the edge, stating this was the problem. Engine shop wanted $5700 to rebuild head replacing all valves while new head with guts quote was $6200. I decided to go for the new as I plan to keep the vehicle. I've been using 91 grade fuel, regular service by dealer and overall babying the car inside and out. What would cause this issue? How to avoid in the future, has anyone else had a similar issue and with what results? Oddly enough a colleague with a 2004 XC70 with 280k km had the same issue with two burnt and chipped valves. He had only the 2 replaced at a cost of $4000. Dealer says it hardly ever happens, luck of the draw? Should i use a fuel additive for a cleaner burn as the valve stem had carbon buildup as well? Feedback would be appreciated.

 

I use synthetic motor oil and was wondering if this would help?

 

After chasing this for months I have come to the conclusion that the #1 cause is oil getting past the valve stem seals. So, leaking valve stem seals cause some oil deposits to get on the bottom of the valves and if it causes enough carbon to stop the valve to seat properly in the head when it's suppose to be closed, it will cause the valve to burn and crack/chip/etc.

Will synthetic oil stop this from happening? Maybe, especially the oils that are suppose to be good for high mileage cars. The high mileage stuff is suppose to have additives in it to help the seals. I now use high mileage full synthetic oil. I have 220,000 miles on that car right now.

I do think the gas treatment that claims to clean valves would help. I use the Lucas stuff every 2,500 miles.

It would be nice if people would give the details on their "burnt valve" issues. Like, mileage, oil type, oil brand, if they use fuel injector cleaner, how often the oil was changed, did they see any evidance that they have valve stem seals leaking like smoke out of the tail pipe at start up, etc.

 

Ditto this,...in some places in NC or SC you can get 98 still. There was also a place near Daytona that claimed they had 100 fuel. Tried it a few times, what an insane difference both in pep, takeoff, and mileage. Huge difference, night and day,...except for the cost made a big impact on all those that used it regularly. Very sure it was Shell,... wish I could get it locally! All E free BTW!

 

I just uncovered a BT5254T2 XC90 valve cover, owner indicates they use 93 Sunoco only, or as best they can. Found one Exhaust valve with like a 1/4 hole on the edge of the face. Cyl #4. Didn't run too well. The only comment I think I can add was in the spaces next to the tappets by the time you got to cyl # 5 there was dry crusty stuff in those spaces. Almost clean next to cyl #1 .

To me this indicates an oil issue, most likely oil starvation by the time it gets to cyl #5 , which apparently is common. This may be engine design. Go visit a salvage yard and see the number of heads and covers that have been removed and in each and every case around 170K the rear part of the head just under the camshaft cover,....there it is,...each and every time a very noticeable difference between the front and the rear. And the ones that I have checked the pump and the oil pan internal o rings look fine. Since so many people ditch their vehicles at around 10 years and many sooner,.... I'm pointen the finger at the small oil passages in the head, it seems that something is going on by the time the oil reaches the cams near cyl #5. It's just that the majority of vehicles, all,...IMO,... are disposed of and this issue has gone undiscovered.


The other thing is, CHANGING the oil pan, cleaning it, new orings seems to help. As of course the pvc system!