Bought a 2007 Suburban at auction. When cranking it sounds asthmatic, wheezing, backfiring, etc. Haven't run a compression test yet. Took off the valve covers, all the rockers seem to be operating in the proper sequence. However, when the engine stops cranking, all the valves are closed, is this normal for this motor?
Update... compression test, 0 on 1, 75 on 2, 90 on 3, 0 on 4, at this point I just stuck my finger over the plug holes, 1,4,7 have no compression, all are low.
Another update... the cylinders that have compression have between 75-90 lbs, and it takes forever to reach that, which indicates bad rings, if I recall correctly.
Pulled the heads, all the intake push rods bent, and you can see where the valves kissed the pistons. 1 and 7 and 4 had bent intake valves.
Per the machine shop, who's seen it often, caused by bad gas after it sat, varnished up the intake valves, causing the rods to bend, then, when they opened, they stuck open, hitting the pistons. Solution, pump out all the old gas, put in good gas, put it back together. He's also seen this happen to trucks while running (this one never started), from old gas in the motor.
The low compression? With the bent intake push rods, the engine isn't pulling in enough air, ergo, low compression.
So, it seems if you have one sit for awhile, make sure it's got good gas in it?
Any thoughts?
Update... compression test, 0 on 1, 75 on 2, 90 on 3, 0 on 4, at this point I just stuck my finger over the plug holes, 1,4,7 have no compression, all are low.
Another update... the cylinders that have compression have between 75-90 lbs, and it takes forever to reach that, which indicates bad rings, if I recall correctly.
Pulled the heads, all the intake push rods bent, and you can see where the valves kissed the pistons. 1 and 7 and 4 had bent intake valves.
Per the machine shop, who's seen it often, caused by bad gas after it sat, varnished up the intake valves, causing the rods to bend, then, when they opened, they stuck open, hitting the pistons. Solution, pump out all the old gas, put in good gas, put it back together. He's also seen this happen to trucks while running (this one never started), from old gas in the motor.
The low compression? With the bent intake push rods, the engine isn't pulling in enough air, ergo, low compression.
So, it seems if you have one sit for awhile, make sure it's got good gas in it?
Any thoughts?
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