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Burnt exh valve 02 6.0L

Discussion in 'Chevy Trucks' started by snow7899, Mar 5, 2007.

  1. snow7899

    snow7899 Senior Member
    Messages: 238

    My 02 GMC dump stated skipping and check engine light came on. I scanned the codes and it came up with code PO305 cylinder skip in #5. I Thought it was a plug or a coil pack. Turns out that the exh valve on the #5 cyclinder had burnt. Has anyone had a problem with skipping or head problems with the 6.0L motor?:cry:
     
  2. Yaz

    Yaz PlowSite.com Addict
    from NH
    Messages: 1,061

    Your the first I heard of that. How many miles are on it? Is it posible somthing else cause the vavle to burn? I would check the Cam and the head itself before having somone toss a new value in there.
     
  3. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    snow, how did you diagnose that it had a burnt ex valve? Do you have the head off now?
     
  4. snow7899

    snow7899 Senior Member
    Messages: 238

    I did a compression check on all the cylinders. #3&7 are both at 175psi. I ruled out a head gasket problem although the truck did overheat with the plow on a couple of times. I did use a scope to look in and the hone marks are still on the walls. The truck only has 49K miles on it. I know both fuel level sensors are bad but should have no affect on the engine. I have not talked to anyone that has ever seen a problem with these heads. I am guessing that a piece of carbon got under the valve, valve stuck open, and overheated it. I'm hoping it did not damage the head itself to bad.
     
  5. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    What was the compression on #5?
     
  6. snow7899

    snow7899 Senior Member
    Messages: 238

    Yes it is #5. I plan to tear it down next week. I'm going to remove both heads while I have the intake off, just to have the other head check for any problems. The only possible cause so far may be carbon deposits, but being an 02 wiith 49K and the oil changed every 2K or 2 months, it doesn't make much sense so far.:realmad:
     
  7. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    What was the actual cranking compression when you checked #5? If #3 and #7 were 175 psi, what was #5? Did you do a leak down test too?
     
  8. snow7899

    snow7899 Senior Member
    Messages: 238

    The #5 cylinder had no compression at all. When I performed a leak down, there was no restriction and was blowing right out the manifold collector. (I had the Y pipe disconected for the test.)
     
  9. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Wow, no compression at all. That's not good. Sometimes you can "clean" the valve seat and face of the valve (if it's not actually burnt) by removing the spring and retainer from the valve and rotating the valve against the seat while pouring Gm's Top Engine Cleaner in the exhaust port. This has worked a few times for me in the past and is actually a GM recommend procedure in an attempt to save from removing the cylinder head.
     
  10. xc23

    xc23 Member
    Messages: 79

    snow sounds like you already did some looking around in side your 6.0 but for what its worth I have a 5.3 in an 01 gmc w/ 80000 on it . She started to skip real bad after a big push . Did the same things you checked come to find out. I had a bad fuel injector #5 CYL washed all the oil out of the CYL gave it an extremly low comp reading . Replaced all the fuel injectors to be safe ( at 96$ each ) now she runs great . Mine also showed the 305 code
     
  11. snow7899

    snow7899 Senior Member
    Messages: 238

    Thanks for the replies, I'll be sure to check the injectors before I reassemble the gas toilet.:realmad:
     
  12. Rowski

    Rowski Senior Member
    Messages: 129

    Before you pull the head loosen the rocker shaft and recheck compression.

    Derek
     
  13. Snow7899

    Anything new to report???
     
  14. snow7899

    snow7899 Senior Member
    Messages: 238

    NEVER ASSUME ANYTHING!!!!!!!!!!!!
    I pulled the truck into the shop to start taking the heads off. Which was diagnosed by the local GMC dealer as a burnt vale. I found a broken exh valve spring!!!!! I did however pull the head any way to inspect the valve and surface area. He was quoted 3000.00 at the dealer which does include a tune-up. Do you think the tech at the dealer knew??? If I didn't care I could have fix the truck for about 10 bucks.
     
  15. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    I'd bet they knew. Since it was diagnosed at the dealer, one of the diagnosis steps when dealing with a dead cylinder is to check the valve train and I bet the technician did. But the 6.0's actually have more valve seat trouble than spring trouble, so your smart to pull the head anyway.
     
  16. Yaz

    Yaz PlowSite.com Addict
    from NH
    Messages: 1,061

    That's great news. Dam tech. Boy that must get you P Oed It get me mad and it not even my truck!

    I bet they charged you somthing for there usless information. Please go to the dealer and get all you money back for there stupidty. I guess it wouldn't be worth your time and just ruin your afternoon or morning.

    So the spring was just not shutting the valve tight. I'll be hon swaggled...Good find. Somtimes we over look the simple solution or the obvos. You said burnt vavle and we all just went along and said.. OK.

    If I were you I would put compressed air in cylinder and pull up the valve and turn it to see if the stem is bent checking for runout. If none and it seals in all positions, I would put it back together with a new spring and not pull the head.

    Good luck!



    Edit: I just read you pulled the head already.... opps my bad.