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

[PeteB]

There is no mention if anyone was having coolant temp issues, I take it this was not the case?

We had a car in our family with bad head gaskets and what I found was that RPM and load
were the major contributor to overall heating. Around town with stop and go, there was
time for the engine to cool down when idling but the temp steadily rose on the highway.

Is it correct to say that this has not been a common problem with these cars in past years,
given that this is not an old thread?
I have to wonder if something has changed in the fuel supply, something to lower the cost
or whatever?

[jblackburn]

Is it correct to say that this has not been a common problem with these cars in past years,
given that this is not an old thread? I have to wonder if something has changed in the fuel supply, something to lower the cost
or whatever?

Seems like it's been an issue as long as I've been here for the higher-mileage cars with leaky valve seals. When I started seeing lots more blue smoke, I knew mine would be joining them sooner or later.

[j-dawg]

Leaky valve stem seals leak pretty much all the time. Which means that any time the car sits some oil may pool up on the valves (to cause a puff), for example when idling at every stop light. Just because you only see a puff of the smoke at certain times, doesn't mean that is the only time there is oil leaking.

True, but low-throttle conditions - eg, idling - exacerbate the problem. Intake manifold vacuum draws oil in around the intake valve seals, and it gets burned off most heavily when you get back on the throttle. This is why you (that is, I) see much heavier smoke after I've been coasting in gear. Stop-and-go traffic in the summer is an absolute smoke show.

I wonder if intake gases are creeping into the head via the same pathway under boost.

[erikv11]

Agreed, you make a good point. I was responding to the misconception that "... the leaky valves are only during start up and there is a lot of time to burn that oil off." Your more thorough explanation reinforces the reality: oil will leak past a bad valve stem seals in many different situations.

[nikolajs]

a) ‘98
b) V70 T5M
c) 169,000 miles
d) 47,000 miles. (Purchased with 122,000 in NJ)
e) 88 “mid-grade” in Utah
f) Sinclair or Tesoro normally.
g) 50/50. Lots of driving up and down steep roads.
h) Average to aggressive.
i) 1-2 people.
j) Utah. Very cold to very hot but normally dry.
k) Valve stem seals and guides in good condition. No smoke.
l) High quality full synthetic (normally Mobil1 High Mileage 10W-30, occasionally Mobil1 5W-20 in cold months.) Oil change every 5,000 miles.
m) Was having intermittent problems with misfiring (codes said random misfires, no specific cylinder). Did full ignition tune up (plugs, wires, cap, rotor etc…), cleared codes. Drove around a while to see if CEL would come back on. Problem started when engine under heavy load: 85+ mph up i80 to the mountains (Parleys Canyon). Probably was in 4th gear, RPMs were probably around 4500. Engine lost some power, CEL started blinking. When exited interstate idle was very rough. Happened in late fall; moderate air temp ~50F; no rain or snow. Did compression test afterwards:

Cyl1: 150 psi
Cyl2: ~20 (audibly not building pressure, can’t count individual cranks)
Cyl3: 149
Cyl4: 151
Cyl5: 148
Wet:
Cyl1: 189 psi
Cyl2: ~20 (audibly not building pressure, can’t count individual cranks)
Cyl3: 200
Cyl4: 220
Cyl5: 172

n) One exhaust valve on cylinder 2 (see photo).
o) Prestone, green. Changed the coolant around 10,000 miles ago (full flush) when did heater core.
p) Just pulled the head, took it to the machine shop today.

[cmblackburn]

Agreed, you make a good point. I was responding to the misconception that "... the leaky valves are only during start up and there is a lot of time to burn that oil off." Your more thorough explanation reinforces the reality: oil will leak past a bad valve stem seals in many different situations.

Well think about it, oil thins out as the engine gets up to operating temperature. It's much more likely to sneak its way past the seals when it is running and hot vs. sitting with thick, cold oil- though it still makes its way through a little bit and causes smoky starts.

[erikv11]

Totally agreed, many of these posts are all pointing out different sides of the same thing: leaky seals will leak all the time but puffs will only show up under certain conditions.

Actually there is really never (almost never) any "thick cold oil" in the upper part of the head, only warm thin oil that got there via the oil pump when the engine was running. Because the oil is left there when you turn off the car, it leaks down the bad seals and pools up on the valve and creates a puff when it burns off at startup.

The oil that leaks and burns continuously is never really seen, it is the oil that arrives in bundles and causes a little puff that we notice. But yes, it is all burning oil, leaky seals will leak all the time.

[mecheng]

I always thought once the car is warm, the valve seals will swell and it won't keep burning oil. Perhaps, people that reported no leaky valve stem seals are not aware that when driving the oil burning can not be seen as per @Erik11 theory. At start up, you can sometimes miss the initial oil puff burn unless you are outside the car. If this is all true, if you have leaky stems, you have to pull the head to change them, which is a big job. If you end up burning the valve, same amount of labor but you may want to change all the exhaust valves anyways.

Regarding the octane, some are 2nd owners, who knows what the original owner used; despite current owner's use of high octane. I continue to recommend high octane also for the extra fuel economy I recorded.

[MadeInJapan]

It is a job but there are ways- such as with a magnet to pull those... we did it on my S70 some time ago but it still detonated the 5th cylinder exhaust valve and I ended up needing upper engine work. Now with all renewed the car is like new in the way it drives and the timing belt isn't due for some time. I never thought it to be an advantage for this to happen to a car but in the long run, it could be if the car is worth saving.

[rspi]

Having pulled several heads and valves for overheated or burnt valves, I think it it is a good idea to pull the head and the values. I don't think I have ever pulled valves and not seen some pitting on at least 3 of every 10 valves. Burnt valve just waiting for the time to happen. Usually under load when they are hottest.

The valves need to be cut and lapped or at least lapped so they can make a good seal.