warthog

98 xj 4.0L 4wd


I have seen on some threads that the normal operating oil pressure at idle is around 12. my idle is around that and my running pressure is right at 40. i dont remember it idling this low till i changed my oil. i have only had this jeep for about a week.
is this normal or should i look at changing something?

also my normal temp is right at 210 and when i sit at idle for 10 to 20 minutes it will go to to around 215 -220. i am use to a toyota and this seems very hot for the engine. i just changed my thermostat and the guy i bought it from said he changed the water pump, radiator and hoses.

does any of this sound normal ??


i am looking for an answer before i head into work in the morning.

(Eckks-Jay)

Oil pressure sounds normal, but from that guage its hard to tell what the oil pressure actually is. Get a mechanical guage to see if it is low or not. The temp should stay right at 210. Did you change the Radiator cap?

warthog

no i didnt change the cap. i didnt think that would have been a factor. i am glad to know that could be an issue now. can you explain the reasoning behind the cap (just for my knowledge). I consider myself a decent mechanic but i dont know much about the cooling system.
thanks

<XJ>THUNDERBAT<XJ>

for every pound of pressure you put on water, it increases its boiling point, thus allowing your water temp to exceed 210 without boiling over

ltlgreenXJ

just thought i would throw my 2 cents of jeep wisdom in here:

any funny noise it makes, it's ok, jeeps do that.
and a lot of jeeps overheat.

ok im done now

xjchris

+ a little over a million

offroadnut36

x2 for every pound of pressure it increases the boiling point by 3 degrees Fahrenheit.

muddeprived

40 running pressure is normal, and it idles down to as low as 10. You are fine there.

Mine stays around 210 but on hot days or long idles will bring it up to 215 or so. It's normal. The 4.0 runs hot in our xj's. it doesn't help that our engine bays are crammed. Hood vents, scoops, etc will help a little.

<XJ>THUNDERBAT<XJ>

mine made it up to 230ish today, pressure tested the radiator cap and it wouldn't go above 10 psi on a 13 psi cap so i got a new one, my fan was really easy to turn when hot as well so im replacing the fan clutch before school tomorrow. I hope to install hood vents within the next two weeks, just can't decide which ones i like best

kurvy

inline 6's are normal for going over the temp gauge. just be cautious when it is close to the red!

and i always wondered about the oil pressure ...

mine fluxes like crazy, idling and running
didnt know idling was below the gauge.

warthog

Preciate all the info, made me feel a little better, thought i just bought a money pit. doesnt sound that way now. i will get the cap tested. can you do that at any auto parts store?

(Eckks-Jay)

Just replace it. They are cheap. but i think that the stock rad cap should be 16psi...anyone else know for sure?

ltlgreenXJ

i thought it was 18psi, but im not sure about that either

Jason248

usually the caps are 16psi but it can depend on the vehicle, regardless it always says right on the cap

Tjheems

You are all fantastic. I had the same question. My jeep will live on!!