Hi,
ive got a 2001 xj. Had the head and gaskets replaced in august 2020. Was running great since. It is at least I thought in otherwise great shape. 130k miles. Started misfiring this week and took it to the shop. Mechanic is saying no pressure is being held - about a 90% leak. He is saying the engine needs a rebuild. Head and gaskets are fine.
What should I do? Have mechanic swap out engine, rebuild engine or sell jeep as is and start looking for another?
help!? Thanks!

 

Do you trust this mechanic? I trust mechanics as much as politicians. Hell, in reality you could have a simple crank sensor failure and this shop wants to take you for a ride. That's exactly what happened to me about 12 years ago when I knew nothing about automobile diagnostics. My 01' started throwing misfire codes and a flashing CEL, then it wouldn't start. A shop told me I needed a new engine. My dad took a look and said, dude you don't need an engine, you're not getting a crank signal. I didn't know wtf that meant but a $30 sensor swap got that Jeep back on the road for another 100K Mi. You might want to invest in a compression test kit, a leak down test kit and determine the health of the engine yourself. You might want to send the oil out for analysis as well. If the motor truly does not have compression in one cylinder, I would look at two options. Dingleberry rebuild or a full rebuild with a stroker crank. No compression in one cylinder is a symptom of either a piston failure/worn piston rings, or a valvetrain part failure like a valve, valve seat, valve spring, rocker arm, push rod or a lifter.

 

Thanks for the info.
Mechanic seems to think the problem is with the rings. They do seem trustworthy, but you’re right - how can one truly know?

 

If you can have your mechanic do the leak down test in front of you, that would be best. If its 90% leaking through the rings, you can pop the oil fill cap off and feel air getting pushed out. If its is actually valve related, you can hear the air coming out the exhaust pipe or throttle body.

 

Test it yourself.

As the other guys are saying, 90% compression loss is absurdly severe.. it takes much less than that to notice your engine aint right.

I had a 00 TJ and one of the valve springs just broke... just one,... only "engine" problem over 302k miles of ownership (and that 0331 head never cracked).. It was a hell of a difference, flashing CEL and all that... but something easily noticed once the valve cover was off and completely gone once it was replaced.

 

more info needs to be provided (to you & us)

what compression pressures for each cylinder wet & dry

detail of leakdown test results

what type cylinder head is on there now ?

90% ?..in one cyl ?... would be a holed/broken piston or valve

 

Thanks.
I don’t have all those answers but the head is from Clearwater.
It’s only from the 3rd cylinder.

 

I think if you built the engine with no rings at all in one piston you would still be better off than 90% leakage. Sounds a lot more like a valve or a hole burned/broken right through the piston. As already stated, more test data is the way to go.

 

If your mechanic is trusted and competent, which sounds likely, he has probably ascertained with a leakdown test he thinks the piston has broken a skirt or similar

ask him what he would do if he was you, and an estimate of how much for him to fit a used engine

a mate of mine just honed up the bore with on a dud piston, and fitted new rings and bearings, think he only replaced the one piston, but he did take the engine out to do it

 

Hell, on a Chevy small block, we took a piston out of a scrap box and put it in with the same rings it had on it and ran it on the dirt track. Talk about barnyard fixes! It ran for a couple of races before the whole engine blew.