Thinking about a '98: Oil pressure ?'s

[axiomatik]

Hey Everyone,

I just joined, because i am in the process of searching for a used Cherokee. I just drove one tonight ('98, 4.0, 86k) that seemed very solid, but I was a little concerned about the oil pressure. While driving, it was a steady 40 psi according to the dash gauge, and at hot idle, right about 10 psi. I've done some searching on here (and read a couple dozen threads on this), and it would appear that the FSM calls for a minimum of 13 at idle, 37 above 1600 rpm, and it would seem that the average values members are getting is ~20 psi idle, ~50 psi running.

So, my first question is, how accurate are the dash gauges. I know factory gauges in general aren't known for their accuracy, but could this be off by that much? Second, the dealer says that when they change the oil, they always use 5w-30, and that is likely contributing. How much of a difference would that make? IIRC, the oil filter was a Napa.

So, could this within normal, or should I pass on this one? Thanks in advance.

- Nick

 

[jeepsrock]

With an engine with only 86k, i dont think oil weight is gonna create a really big varriance especially when the jeep is warmed up. It is more likely that the oil pressure sensor is a bit off, if you are interested in the jeep, maybe you can take a spare sensor and try that if they let you.

My oil pressure on my 94 ~120K is usually 20hot idle and above 40 running.

goodluck
Peter

 

[wilsel]

My 97 had the same numbers, and I drove it with those #'s for years without a problem. More than likely its the oil pressure sending unit (they suck on jeeps).

 

[ebxjbob]

I agree, the 97 I have right now seems to run like that, 40 or a little above cold, a little above 10, prob 13-15 at hot idle, runs fine, 139,000

my 96 runs 60 cold 20 hot idle, 178,000

prob a matter of the sending units, the one in my 96 is new because i did the cluster swap

 

[RichP]

The only way to really find out is put a mechanical sender on there and a real gauge. I run about 12PSI by my gauge in my 98, above 40 on the hi-way at anything above an idle, same on the TJ. The oil filter brand also has a lot to do with it.
I put a purolator 'pure one' on the TJ two changes ago and the pressure dropped thru the floor after about 40 miles, put a mobil-1 filter back on and pressure came right back up to normal ranges. I've not had good luck with Purolater filters in either the XJ or the TJ, both took along time to build pressure on first cold morning startups, 30+ seconds and made me squirm watching it crawl up in the morning...

If it's got a Fram on there get it off and put a Mobil-1, K&N, or so I have read, one of the WIX/NAPA golds on there.

 

[1985xjlaredo]

How much do they want for the 98
XJ

 

[axiomatik]

they want $5900 for it, 4dr, 4wd, a/c, power windows/locks, super clean body, etc......

 

[axiomatik]

hey, if anyone else has opinions about this issue, I would appreciate them.

Thanks

 

[fender]

My 98 reads about 10psi hot idling and has for the last 190K+ miles. The factory idiot gauges are estimates at best - plug in a mechanical if you are concerned as stated above, otherwise it sounds like a typical jeep and a fair price - not a steal but not bad either.

 

[ebxjbob]

$5900...whats the mileage

I just got a 97 country with every option but the 242 tcase and upcountry package w/ 139k for $2900

very clean body, just a bubble or 2 on the roof

 

[axiomatik]

it's got 86,000 miles on it, lowest I've found within 75 miles of me.

 

[UNCC_99XJ]

Those numbers don't sound out of the ordinary. My 99 runs at about 20 psi or so when it's good and hot and just over 40 when i'm crusin.

$5900 for one with 86K? Not a bad deal at all. I've got 86 on mine right now and havent had a single major issue out of it.

 

[axiomatik]

well, if the xj I drove had showed 20 psi, I wouldn't be worried, as that falls with the factory specs. However, it was showing 9-10 psi at idle, which is below the the 13 psi minimum the FSM specifies. I've asked the salesman if it would be possible to measure the oil pressure with a mechanical gauge, I'm waiting to hear back from him right now.

 

[axiomatik]

well, the salesman called me yesterday and told me that they changed the oil from a 5w-30 to a 10w-40 and now the oil pressure is 15-16 psi at a warm idle. I'm going to go and check it out as soon as I can (unfortunately, the dealer is an hour away).

 

[UNCC_99XJ]

Chances are you still have nothing to worry about. I'd snatch that jeep before someone else does!

 

[x99j]

i agree you probably have nothing to worry about! i got a 99 that is 20 at hot idle, but i have seen the 4.0l run for years with alot lower at idle. it doesn't mean it was abused (although possible). if the rest of the car is in good condition then the motor probably is to. take the oil fill cap off and look down in with a flash light. that is a rough estimate about what kind of shape the motor is in. if you see lots of sludge then you know why the pressure is low. on the other hand if it is clean as mine is at the same mileage of 86k, then you know you probably got nothing to worry about. could very well be a variation in the guage or sender. mike