noob needs help with mileage - only 10 MPG!
rmchrgr,
What my mechanic had to say was very similar to what you wrote above.
Hey, sometimes I guess right. :thumrigh:
He said that the high leak down percentages are probably due to worn rings and/or valves, but that he can't be sure without taking the head off. He said that worst case I'd be looking at about $2,000 for an engine rebuild/reman.
Does that sound like a reasonable figure?
I guess it's reasonable, I have never priced a Slant 6 rebuild myself. Stuff adds up quick - gaskets, freeze plugs, rings, valves, timing chain etc. All kinds of stuff that you don't think about until you have to rebuild. Plus, he has a car that has to get pushed around the shop/yard or stays on the lift until it's done. A head rebuild could be pretty quick but doing rings is definitely time consuming. There's a lot of clean up involved too, use of special tools, fluids, etc.
Cool that your guy is willing to do it, lot of guys would say no way for whatever reason - not worth it, can't get parts etc.
And the idling rough when warm thing, maybe "idling rough" is not the best way to describe what it is doing. From a cold start the engine sounds fine when idling or revving. When the engine warms up it makes a sound like engine knock when indling, but not when revving. When I picked it up from the shop where I had the work done I started the car and left it idling in park while I talked to the mechanic. Sure enough, once the engine warmed up it started making that engine knock sound. The mechanic had just explained to me that the high leak down percentages were probably due to worn rings or valves, and he also said that worn rings, once the engine warmed up, could explain the knocking-like sound. To those of you work on engines, does that make sense?
No, that does not really make sense. A knock is usually something like a bad wrist pin, rod or crank bearing or some other mechanical malady. Worn rings do not usually make noise themselves. A tell tale sign of bad rings is blue exhaust smoke.
I'm gonna go out on a limb here and suggest that it's possible the timing chain jumped a tooth or has a lot of slack. That might explain your leak down numbers, knocking noise and poor mileage because the engine is not timed right. It would still run but pretty crappy. It's not real likely given that the car runs OK at first and usually there is a hard start condition associated with that scenario. Regardless, a new timing chain is part of any real engine build. A quality chain is good investment.
Can you tell where the knocking noise is coming from? You could check into it yourself. If you have a long extension, you can put one end of it at various points where there are moving parts, then cup your ear around the other end of the extension and listen for anything that sounds wrong. Can you hear it under the front cover or is it more evident under the valve cover/engine block? Just watch the fan!
