The Stovebolt Site Forums The Shop Area Engine Shop Pop goes the engine

I was going down the hill by my house a few minutes ago in second gear, foot off the brake pedal. All of a sudden, the engine/exhaust got fairly loud. Crap, I thought. The donut must have popped loose.

I got it into the garage and lifted the hood while it was still running, and of course, couldn't see anything obviously amiss...until I raised up and looked toward the back of the truck - blue smoke.

Does anyone have a clue as to what happened?

I remember something about oil getting into the cylinders going down hill, or something of the kind. There was a thread on it not too long ago.

Oy, vey. Time to break out the compression tester. Start by checking your fluid levels.

Describe the noise that first got your attention. Do you hear any new noise from the engine- knocking, rattling, tapping, clunking? Does any new noise change with light acceleration and deceleration- under road load, no load? Is there any misfire? Remove the spark plugs and look for oil on any of them. A spark plug wet with oil may indicate broken piston, but other possibilities also exist. A compression check is in order, as mentioned by hotshoe, but it may be appropriate to do dry and wet compression checks, and/or a cylinder leakage test.


Harvester

The noise was like an exhaust pipe came off up front. No tapping, clunking, rattling or knocking. Like I said, I was in second gear, using the engine to slow my descent down the hill.

I haven't had a chance to do anything yet, but I see where you're going. A broken ring, maybe?

Tom,

A broken ring could account for the blue smoke, but wouldn't account for the noise. You wouldn't hear anything from broken rings. Based on your description of the exhaust sound, I wouldn't discount anything in the exhaust system. Mufflers have a way of losing internal parts, depending on the muffler, and changing their sound as a result. Check the spark plugs for oil. A spark plug wet with oil is a bad sign.

Harvester

Harvester, go to the head of the class! I pulled the plugs and all looked fine. no oil in the antifreeze. No water in the oil. I crawled under the truck to see if the exhause pipe had broken, and when I touchedit, it moved. Back up top I checked the flange, and sure enough, the nuts were loose. I tightened it back up and all is good. I just got back from a trial run and it went well.

As for the blue smoke, I just don't know. It's not doing it now.


Thanks to you all for your input! Stovebolters are good folk.

Did you do what you were doing in the first place going down hill?

No. I didn't want to push my luck. I was in second again, but I kept my foot on the gas pedal.

Tom,

Glad to hear you found the cause of noise. Its always good to hear that our suggestions actually help find a trouble. The blue smoke is reason to do dry and wet compression checks. Try the deceleration again as you did previously, and look for smoke. Blue smoke under prolonged deceleration most often, but not always, indicates leaking rings. The dry and wet compression checks will help identify that condition.

Harvester