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Why does my XC burn through exhaust valves? V70-XC70 1999

Hello All,

I have a 1999 V70 AWD XC wagon. I purchased it used with 12,000 miles. Since I have had the car, I have religiously changed the oil with full synthetic every 5,000 miles. I also ran the car on 87 octane, thought Volvo recommended 91 (I believe). At 163,000 miles the compression in cylinder #1 was bad due to burnt exhaust valves. I had all the valves replaced along with valve stem seals and had the head machined. 30,000 miles later cylinder #2 was diagnosed with poor compression due to burnt exhaust valves. At the time, the cylinder for #2 was full with a pool of oil. This was not due to worn oil filler gasket. I replace the oil filler gasket every 30,000 miles when I turn the car up. My mechanic did check the piston rings and they are in good shape and not the cause for the presence of oil in cylinder #2.

I am having all the valves and valve stem seals replaced and I am also having the head machined. My mechanic who did the last valve job said he has seen XC wagon burn up exhaust valves. My questions are:

1) Has anyone else experienced repeated episodes of burnt valves on the early XC models?

2) I have been using 87 octane all along. Could that be the cause for why I am burning through exhaust valves? If it is, why didn't I burn through the exhaust valves sooner than 163,000 miles and of course, the next question is, why did the valves only last 30,000 miles?

Thanks in advance to all who reply.

Hugh








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    Why does my XC burn through exhaust valves? V70-XC70 1999

    Hugh - Ask your friend how the engine reacts when one does use lower octane.

    Ask your friend how lower octane does affect the car.

    Does it reduce mileage?

    Here's a good one for him - will ignoring a low tire monitor affect the door locks? One day, my wife and I were going to a play. When I took off, I sensed a flat tire, as I backed into the driveway, the warning came on.

    We took our other car.

    The next morning, the car would not unlock, I had to use the emergency key. My dealer and people on this board did not know of this behavior.

    One week after I had the tire repaired, I flattened another tire - once again, the doors would not unlock!

    My son-in-law is a senior Subaru Tech - He tells me that in Subis, the same computer runs the tire monitors AND the door locks.








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    Why does my XC burn through exhaust valves? V70-XC70 1999

    I differ from most people on the topic of not using the proper octane gasoline.

    I have only read one explanation of how a knock sensor stops preignition - In one Chilton Manual the text explains that the first thing that occurs is that extra gasoline is fed into the cylinders to cool them. Adjusting the timing automatically DOES NOT stop preignition, as the cylinder is firing BEFORE the ignition sends a spark.

    It could be that preignition is burning the valves.

    No manufacturer publishes an octane recommendation unless some sort of bad things happen if you do not follow them.

    BTW - I use Sonoco 260 in all my vehicles - I get better mileage and I know that as an engine ages it gets carbon and other stuff that causes preignition - hence, the requirement for higher octane goes up.

    Every time I get gas, I write my mileage on the slip. On a trip across Canada, all highway driving, I got one tankful of regular from a pump using French language. That tankful got 3 MPG less.

    Percentage wise, the difference between grades is not as great as it was before the 70s.

    At $3.00 a gallon, with a car that gets 25 MPG - one MPG is worth 12 cents. At $.50 a gallon one MPG was worth 2 cents.













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      Why does my XC burn through exhaust valves? V70-XC70 1999

      James,

      Thank you for your reply. You have got me thinking perhaps on my XC, when I get it back, I should run it on 91 octane. I have two '96 850 wagon. One has 405,000 miles (I purchased it new) and the over has 325,000 miles (I purchased it used with 50,000 miles). Both cars are non-turbos. The owner manual for both cars recommend 91 octane. Years ago, shortly after I took delivery of the cars, I was at an Open House for Volvo Owners at Volvo's headquarters in Rockleigh, NJ. A Volvo engineer in response to a question, said you could run the 850 on 87 octane without damaging the engine. With my finger's crossed, that is what I have been running my cars on, and I haven't had any problems with valves.

      As I mentioned, I have been running my '99XC on 87 octane since I purchased in 1999, used with 12,000 miles on it. After I posted my query above, I had a friend of mine who works for corporate Volvo ask one of the Volvo engineers if running my '99 XC on 87 octane versus 91 octane could have caused the exhaust valves to fail? The response back I was "no". Running my '99 XC on 87 octane should not damage the engine.

      With all the said, maybe I should still "bite the bullet" and just pony up the extra money and purchase 91 octane with the hope I am avoiding an expensive valve job down the road.

      Hugh








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    Why does my XC burn through exhaust valves? V70-XC70 1999

    Either your mechanic put in the wrong valves, the machine shop did not use the correct metals for the valve seat repairs, or the oil/coolant passages are clogged. For the last one, it could be that sealant used in the cam cover may have been put on too thick and covered some of the holes around cylinder #2.

    None of the above is your fault. Using hotter burning 87 octane in your LPT for 30,000 miles didn't cause it either. Highway driving, under 3000 rpm, with 87 octane shouldn't cause any problems, the hotter 87 octane will cause trouble between 4-5000 rpm. I see no concern for those who use 89 octane and like high rpm.

    Why would you need new valve stem seals? They are typically good for 200K+.

    --
    Keeping it running is better than buying new








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      Why does my XC burn through exhaust valves? V70-XC70 1999

      Klaus,

      Thank you for your reply. I do flush and replace the coolant every year just before the onset of winter. So I hope that prevents any blockages in the cooling passages. With regard to replacing the valve stem seals, it was recommended by my mechanic to do so.

      You know, one of your comments about using the wrong valves is resonating with me. The last time I had the valves replaced, I had my garage supply their own valves, instead of insisting on using Volvo valves. At the time, the head was off and the garage wanted to immediately send it out to the machine shop. If given more time, I could have obtained Volvo valves, but instead I used the valves supplied by the garage. The same thing happened again with the current repair. The head was off, and again my garage wanted to get it out to the machine shop. I specifically asked if the valves my garage used were of good quality, since they were not "Volvo" valves. I was told "yes" and that they are used on all valve jobs the garage handles and they have not had any problems. I hope I did not make a mistake by not insisting only on Volvo valves. I guess I will find out.

      Klaus, thank you again for your reply. Just the other s who have responded, I always learn something.

      Hugh








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    Why does my XC burn through exhaust valves? V70-XC70 1999

    1. NA to me

    2. Using 87 octane could cause the valve stem seals to leak. Not sure about the exhaust valves themselves. I used mostly regular gas (87 octane usually) in my 95 850 for a long time. Based on Klaus’s recommendation, I switched to premium or 91 octane. Unfortunately, it was too late as the valve seals started leaking around 230-240k. If I had a chance to do it over again, I would, without question, have used 91 octane from the time I bought the car. Definitely believe that the use of regular in those early 5 cylinder engines will cause valve seal leaks.

    Sounds to me that the engine work wasn’t done correctly at 163k. The new valves should last a lot longer! Mechanic should discount the new repair at a minimum.

    Jim
    --
    Will I buy another Volvo??? We'll see....








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      Why does my XC burn through exhaust valves? V70-XC70 1999

      Jim,

      A friend of mine works for corporate Volvo. Since I origniamally posted my query, I asked my friend to ask the engineers of running an early generation XC on 87 vs 91 octane would cause the valves to fail prematurely? The response I got back was "no". Running the engine on 87 octane should not have an adverse effect on the engine.

      I am getting the car repaired again. I hope "history does not repeat itself".

      Thank you for your response.

      Hugh







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