Using coolant, cyl 1 loe on compression

Desert4x4 · May 24, 2015

99 xj 4.0

It uses coolant slowly, like the overflow tank will be at low after maybe 2 months. Compression test indicated 120 on cylinder 1 and 150ish on all the rest. Spark plug in cylinder 1 has extra rust colored crap on the ceramic and ground strap. So do you guys think I need a new head gasket, or cracked head? Its runs great, occasionally on hot restart it will hesitate for a few seconds and have a slightly rough idle. I'm assuming that's some coolant leaking into the cylinder. An oil analysis through blackstone indicated 0.38% coolant contamination.

Thanks.

md21722 · May 24, 2015

Pull the head and have a look. Take the head to the machine shop, have them magnaflux it, and if no problems found, a valve job and put it back on.

I've heads that are known to crack turn out to be no more than a head gasket, heads that aren't supposed to crack be both head and head gasket. I've also had it the easy way. Valve job, surface, and bolt it back on.

CharlesS · May 26, 2015

Desert4x4 said:
99 xj 4.0

It uses coolant slowly, like the overflow tank will be at low after maybe 2 months. Compression test indicated 120 on cylinder 1 and 150ish on all the rest. Spark plug in cylinder 1 has extra rust colored crap on the ceramic and ground strap. So do you guys think I need a new head gasket, or cracked head? Its runs great, occasionally on hot restart it will hesitate for a few seconds and have a slightly rough idle. I'm assuming that's some coolant leaking into the cylinder. An oil analysis through blackstone indicated 0.38% coolant contamination.

Thanks.

Not knowing exactly when your '99 was built; the later '99-01 XJs had a problem with the heads cracking. The newly redesigned heads have a 0331 that can be seen thru the hole in the valve cover where you add oil.
Since you have had the test done and read coolant contamination; definitely have the head inspected and magnafluxed to verify if it's cracked or not.

Using coolant, cyl 1 loe on compression

Desert4x4

NAXJA Forum User

md21722

NAXJA Forum User

CharlesS

NAXJA Forum User

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