Craftsman LT1500 blowing blue smoke and oil from breather

1MowerGuy

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  • / Craftsman LT1500 blowing blue smoke and oil from breather
First post, looking for some good advice.

Machine in question: 2013 Craftsman LT1500, 17.5hp 420cc single cylinder engine.

Ran like crap this spring. Found HEAVY amounts of oil in the intake - coming from crank case breather tube. Disconneced the breather tube from inlet, and its blowing lots of blue smoke and spraying oil everywhere. Exhaust from the muffler is NOT blue in color and appears normal. With the breather tube disconnected from the intake, it runs better. Not normal, but better.

So I have excessive pressure in the crank case. These engines are notorious for blown head gaskets. Order a new one and installed this weekend. Old one is...suspect. Not new/good. It shows its age. But it definitely doesn't show obvious tell tale signs of being blown either. Hmmm. Anyway, I got it installed no problem. But it's still blowing blue smoke and oil from the breather tube.

Alright, maybe the rings are shot. I don't have a leak down tester but I grab my compression tester and it shows 95psi. This is probably a bit low but definitely higher than I expected to see if the compression wasn't good.

As I say, I don't have a leak down tester. Always wanted one, though, and this was a good excuse to order one. It's on its way to me know. In the meantime, though, should I be checking something else?

Feedback is welcome.
 

bertsmobile1

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  • / Craftsman LT1500 blowing blue smoke and oil from breather
Did you check the head & block for flatness ?
These engines have a bad habbit of going hollow along the wall between the push rod tunnel & the cylinder.
About 1 in 3 that I do requires lapping on either the head, block or both.
After that the tightening sequence is fairly critical, 3 or 4 steps in the correct order.
And did you get the correct gasket ?
None of them fit particularly well
On one particularly troublesome engine I had to resort to a hand cut copper gasket.
 

1MowerGuy

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  • / Craftsman LT1500 blowing blue smoke and oil from breather
Your question regarding correct gasket is certainly valid. I did a bunch of research before buying and I'm quite certain it was the right one. Was an exact match with the old one when put back to back. And I did tighten it down gradually, in a cross sequence. I feel quite confident that I at least did that correct! I've swapped head gaskets previously so it's not my first rodeo from that standpoint.

I did not check for flatness. Didn't realize that was a potential issue. Thanks for the heads up but if it comes to that, I'll likely ditch the machine and start fresh with a new one. I'm certainly willing to swap a head gasket, and I'd likely install a new piston and rings if needed. Probably wouldn't go much further than that.

Leak down tester will be a big help in determining where to go next.

Really appreciate your advice.
 

1MowerGuy

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  • / Craftsman LT1500 blowing blue smoke and oil from breather
I know I'm bringing up an old thread but thought I'd provide an update in hopes it helps someone else out somewhere down the line.

Leak down test confirmed that the rings were bad. Very bad. I was losing 80 percent thru the rings. Found a respectable small engine repair guy near me who installed all new rings, re-honed the cylinder (the cylinder was fine otherwise, no scoring or gouging), installed ALL new gaskets throughout the engine, new oil/filter, new fuel line and filter. All for $200 parts and labor. I was pleased with the price and the mower runs great now.
 
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