Burned Valve Database DATA ONLY or a P0455 code will be set

[jimmy57]

This is a reply from 2 years ago in another thread on this topic.

Re: 2 burned valves in 12 months! what is going on?

Post by jimmy57 » 11 Feb 2017, 13:44
In recent years where burnt valves are not a given at 100K miles or less, the vehicles that are run at low revs and low throttle and then run at highway speeds, usually with some load, are the ones burning valves. The valves get face deposits and the lower engine speed does not cause the spring wrap that rotates valve for seat and face cleaning. Then you go run at higher load or uphills and the increased heat and flow burns the valve like a cutting torch was taken to valve. The older less hard valves would get V notch cracks. Octane can contribute as lower octane causes retarded timing and retarded timing increases exhaust gas temps since the burn completion is later and thus it is still hotter when exhaust valves opens. I have seen plenty of burnt valves on vehicles I know the owner to run high octane fuel in. Stem deposits and valve guide wear are other things contributing to or causing burnt valves. And there is seat or face wear that decreases lash and decreased lash lets valves stay on seat for cooling a briefer period. Wear on face of valve can go through the face hardening and result in lower temp needed for valve failure.

[abscate]

Jimmy - I think the cure for this is to get the car up to 4000 rpm for at least 10 minutes or so once a month?

On edit - this is from The Queen of Volvos, June. We should listen to her for her longevity record includes the most Volvos rolled over.....

I was instructed by my Volvo dealer service to reseat and remove deposits from the valves to run the car in second on the highway rpm at 5000 for five minutes without interruption and ac off.

Then the valves would reseat. It worked like a charm and the car would idle smoothly and start right up cold for a while.

I noticed car needed it every six months or so. I did a lot of one mile trips per day with that car. I would think it would cause extreme heat and pressure incinerate any deposits during those five minutes.

[jimmy57]

Yes, that is exactly what I was talking about. Rocker arms were always set with a touch of geometry that made valve move, at least in the 50's 60's and later when it was figured out. Bucket tappets work squarely on the valve and reduce guide wear but the only way to get any rotation that will rotate and clean seats and valves is to have a little spring wrap and resonance. This only happens at higher revs. I have not known volvos to get a very rough idle but the presence of engine idling is reduced after the spirited drive. I have no idea why the service advisor would mention turning engine off. I think he got emissions monitors completion drive instructions mixed in with valve cleaning drive.

[abscate]

Thanks jimmy, Ill put a thread on this together for reference.

Im sure you are right and AC OFF was for drive cycle reasons.

[June]

Thanks jimmy, Ill put a thread on this together for reference.

Im sure you are right and AC OFF was for drive cycle reasons.

Since you quoted me on this subject I thought I would add I have always run my S80 at 5000 rpm for five minutes a couple times a year. (Right after a oil change always) At 196K miles on my original 2004 engine, turbos, oxygen sensors, and catalytic converter obviously it hurts nothing. I will admit the 5 cylinder in that V70 used to make me nervous as it felt I was running it hard whereas the 6 cylinder in the S80 it is unnoticeable. June

[bmdubya1198]

Well fortunately I have no worries with that... I run my car to reline almost daily. It's just too easy... even easier than my happy-to-rev Miata was.

[dobrosailor]

1998 v70 glt auto
burnt valve at 166k
Premium gas
daily driver around town and country roads, soccer mom stuff, live on steep hill up and down several times daily.
If I remember right it was second cylinder from timing belt.
No oil burn blue smoke

[abscate]

1999 V70 T5
Burnt valve at 256k
Daily driver mostly highway miles at 70 mph
#3 cylinder
Valve stem seals were gone, bad smoke on 19W-30 syn, ok on Castrol HM synthetic
Either 93 octane or poor mans 90 octane ( half 93, half 87)

a) 1999
b) V70T5
c) 260,000
d) 250,000
e) 89.93
f) Mobil Sunoco
g) 90 highway. 10 town
h) Passive
i) usually solo, occasional 500 # boat tow
j) Chicago to DCyo Boston highway cruising
k) leaky valve stem(s)
l) Mobil one HM
m) on way home on interstate, jerk, constant miss
n) don't know how many valves burned. #3 no compression, one exhaust valve
o) Volvo,coolant, 2 year change interval
p) cylinder head job,three new Volvo exhaust valves

[mecheng]

Updated Pareto graphs

[abscate]

1999 v70mBase automatic burned #3 valve at 252,000 miles, used 87 around town and 91 highway