J230 Oil Pressure drops as Temp Increase

[rhtrudder]

Got a mate with a 230 , engine recently rebuilt but now noticing oil pressure drops way off as the oil temps goes the other way , no noticeable difference in the way it runs , could it be a wiring problem 

[RFguy]

suggest changing the title of your post.

PLEASE be more specific in your title of the post

 

[KRviator]

Nope. Increasing oil temp = decreasing oil pressure. My Landcruiser does the same, indicates high until the oil temp gets to the normal range, then sits dead on the quarter mark on the gauge unless I give it a bootful.

A wiring problem would likely manifest itself as either no oil pressure, or high pressure that doesn't change, depending on the sensor used.

That being said, you don't say what it is after start nor what it drops down to, nor what pressure sender you have (though if it's been properly rebuilt I'd expect it to have the Jab-issued sender, but that's not a given)... The oil pressure limits are 32-51 PSI under normal operations, with as low as 12 PSI allowed at idle and 76 PSI after start with cold oil, so dropping from 70 PSI to 40 isn't cause for concern.

[facthunter]

Pressures and Temps Please. You COULD have  a crook pump, bearing(s) with excess clearance or a faulty Relief Valve. IF it's always related to temps and rev's I'd rule out the Indication aspect. Don't just keep flyjng it. FIX the Problem. Cut the Filter and check for Metal. How long has it been like this?  When dd the change get Picked up?  Nev

[onetrack]

Was the oil pump replaced? A worn oil pump will make the oil pressure drop as the oil warms, and especially as the engine RPM's reduce.

A lot of people think it's O.K. to re-use an old oil pump, "because it looks good".  But only careful measuring and checking for scores in the housing/s can provide the information needed, as to whether the oil pump is within specifications or not.

[rhtrudder]

I think he will hook up another pressure gauge, can it be done with a mechanical one which I guess would screw into where the electric sender is, should give us a definitive answer

[RFguy]

-yeah get a 2nd opinion on the pressure using another sensor

- what oil is in it? (100/W100/15W50/ W120 etc

- what is the ambient temp at starting ?

- jab PRVs can be troublesome.

- gen1,2,3,4 engine ? (oil  pumps changed)

just rebuilt...suspect ! something going high flow/ high clearance etc (bad !) 

 

there is a specialist group at :  JabCamit.groups.io   suggest that.      [email protected]

[BrendAn]

Check what oil is in it, as Rf said.

Before you worry about anything else.

[Moneybox]

3 hours ago, BrendAn said:

Check what oil is in it, as Rf said.

Before you worry about anything else.

You can expect a change in viscosity as the engine oil temperature rises however using the correct grade of oil can make a big difference. There may also be excessive bearing (or other) clearance allowing the pressure to drop once the oil viscosity changes. There will be a minimum allowable oil pressure and with a new rebuild you should be well above that. Some after market oil filters can create a problem.

[RFguy]

oh, and in additon to my questions,

what are the oil temps displayed at different pressures ?

is it RPM dependant above 1200 rpm ?

was the sender replaced at overhaul ?

the vdo sensors develop wear regions on the metering track, need to be replaced once in a while dependin gon vibration modes they're exposed to

glen