View Full Version : oil pressure
13-02-2003, 07:34 AM
i know this has been done a thousand times before in many different ways but im interested.
oil pressure in a tj 1997
the guage reads from 0-30-50(the no's on the guage)
my guage sits at 30/40 on startup
when it gets warm comes down to 20 at hot idle
how does everybody elses read ????
i know that the guages in tjs are not that good and reading s vary quite a bit
but humour me
13-02-2003, 08:50 PM
Just remember that when oil is cold it is naturally thicker so you will get an early "false reading" when it is warm that will be the true oil pressure reading and that is the one to rely on.
Oil viscosity is determined when oil is at its normal operating tenmperature not when it is cold.
If in doubt or concerned go get a VDO oil pressure guage and connect it up for a day or two and compare variations between the two
all you need is a guage (electronic), sender unit and a T piece so that you can hook up both original and duplicate sender units power up second sender unit and away you go
can power it uyp direct off battery (nothing fancy is needed)
When happy disconnect second guage and associated fittings
14-02-2003, 01:29 PM
Mine reads exactly the same. According to manual(s) this is supposed to happen. Only problem I have had in this regard is when the oil pressure switch broke and pressure climbed to max pressure under any acceleration.
14-02-2003, 01:39 PM
well with my gauges playing up, i have been getting excessive highs and lows i oil pressure and engine temp, goes from no oil and screaming hot (with check guages light on) back to normal and up again. pain in the arse actually, need to pull it all out and give the teminals a good clean.
14-02-2003, 08:16 PM
Ensure new motor oil and filter or oil and filter that have not had more than 20 hours run time.
Run engine to normal operating temperature.
With the motor running, factory recommended oil pressure is between 207 - 552 kpa (30 - 80 psi) at 3000 rpm.
I found the OE oil pressure sender switches on the 4.0 motors gave trouble and replaced them with VDO senders.
Initially I used Autometer guages but they did not perform well in wet, dusty and muddy conditions. VDO make very fine analogue guages and they never failed on me.
VDO swithes are cheaper than OE but you will be up for a guage as well.
If you are experiencing great variation in oil pressure readings, the sender is likely, but not necessarily, the culprit.
15-02-2003, 01:10 PM
no my pressure is good ,i was just interested to see what other peoples 97 tj were reading on the guage at hot idle
with good or bad guages
21-02-2003, 11:18 AM
Also check your oil level - don't overfill! If you overfill you will find that after a short period of time your oil pressure will drop... keep it between the high and low indicators on the dip stick - more oil is not a better thing when the crank shaft foams it up and reduces it's lubrication effect...
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