98 V70 AWD LPT Generic Burnt Valve Question

[rmmagow]

Is there any particular reason to think that a burnt valve is definitely going to happen someday on these engines or am I just seeing the results of forum chatter from the very few that actually suffer from this problem?
I'm at 216K miles, everything is running pretty much OK, oil changed regularly with synth, med grade gas all the time, even tranny fluid gets regular drain-n-fills. I drive my car fast but not hard, few full throttle runs and I always let it warm up for 60 seconds and cool down after driving for 60+ seconds. No heavy acceleration until full warm.
So my real question, can I hope to get 300K out of this mill? 250/275 would probably bring me to retirement and no more 600 mile a week commute. As far as I know, the engine has never had the head off.

[E Showell]

Depends. My theory -- not verified -- is that the valve stem seals degrade with age and are subject to failure. That does not appear to be the case universally, however, so there are probably other factors. I believe with mine it was a failed front 02 sensor which failed so gradually as not to throw a CEL and/or code enough in advance of the valve burning so as to be informative.

Have you replaced your 02 sensors every 100K miles? If so, you might have a shot at avoiding the dreaded burned valve. For what it is worth, mine also failed instantaneously while I was flogging the engine pretty hard on the highway at c. 85 mph.

[cn90]

There are all kinds of theory in the other thread:
- Defective valve stem: well not defective but eventually they die like human beings at certain ages.
- Leaky Seal ---> oil coming down
- ? Bad gasoline

There is an article written by Larry Carley:
http://www.kiwicylinderheads.com/Tips/t ... arley.aspx


For now, I only use Octane 91 and pray I never have to take the head off lol.
I am capable of fixing the head but I have no appetite for it...

[mecheng]

Depends. My theory -- not verified -- is that the valve stem seals degrade with age and are subject to failure. That does not appear to be the case universally, however, so there are probably other factors. I believe with mine it was a failed front 02 sensor which failed so gradually as not to throw a CEL and/or code enough in advance of the valve burning so as to be informative.

Have you replaced your 02 sensors every 100K miles? If so, you might have a shot at avoiding the dreaded burned valve. For what it is worth, mine also failed instantaneously while I was flogging the engine pretty hard on the highway at c. 85 mph.

Is the theory you were running too lean?

[mecheng]

There are all kinds of theory in the other thread:
- Defective valve stem: well not defective but eventually they die like human beings at certain ages.
- Leaky Seal ---> oil coming down
- ? Bad gasoline

There is an article written by Larry Carley:
http://www.kiwicylinderheads.com/Tips/t ... arley.aspx


For now, I only use Octane 91 and pray I never have to take the head off lol.
I am capable of fixing the head but I have no appetite for it...

Is your thought leaking seal causes oil deposits and then poor valve sealing?

[E Showell]

Yes. I believe I was running lean -- I was getting great gas mileage and was just thinking it was my mad driving skills.

[mtd240]

I'm with E Showell on this - my fuel economy dropped 1-2 mpg when I installed the new front O2 sensor as preventative maintenance ~140k miles.

On my 240, the O2 sensor gives worse fuel economy when failing - seems to fail in the opposite direction on the P80s?

I run premium gas (usually ends up being 93) and use 5w-40 Rotella T6 every 5k miles. Hoping that'll keep the valves happy for many miles to come.

[mecheng]

I think the following should help prevent burnt valves:

1)The occasional "Italian Tune-Up" this means keeping the revs up so with an auto choose D3.

2)Running fuel injection cleaner, I wouldn't use the solvent stuff. I like Lucas Fuel treatment as it has oils to lubricate the seals, fuel pump and upper cylinder. The solvent only cleaner I think will dry the rubber seals.

3)Keep your cooling system running properly: proper mixture and fluid changes

4)Try to avoid hot climate - stop and go traffic, this will cause the heat to produce a lot of heat

5)Use 89 octane minimum on turbo cars.

Not sure what Robert concluded on his T5 Valve Job project. There is one theory that plugs may cause this, I guess if they are the wrong heat range but otherwise I doubt. Robert care to chim in?

Check out his videos, it shows the burnt valve:

[rmmagow]

First thing I'm going to do is change the front O2 sensor. My mileage has been creeping up from 22.5 to 25 MPG with no change in driving habits. I'm not afraid to pull the head, just would like to not bother until I can have some good downtime to play. A lady in the area has a 98 AWD like mine with about 160K or so on it and she said it had burnt a valve. Right now she wants too much for it but I hope to be able to wheeler-dealer her down to some nice low number and learn how to pull and fix the head. Looks a lot easier than my old V6 Mazda, only the camshaft things got me confused but I'll work that out too. I'm going to keep my lead foot a little lighter too until the O2 sensor is swapped.

[cn90]

I agree with the mechanical engineer...

- Weekend "Italian Tuneup" on the highway...(watch for cops lol).
- Octane 91+ gasoline.
- Pray like crazy I don't have to pull the head.