Strange Oil Pressure Issues - Help Troubleshooting

[TRD ke70]

while you have the sump off it, check the bearing clearances as well. Plasti gauge (google it) should give you a quick answer.

sounds like a worn bottom end to me.

 

the hole in the head of the bolt/nut is the back side of the pressure relief valve, it's there so there's no pressure on the back side of the valve when it's operating {if that makes sense?)

[ms85er]

hi again all,

 

I have replaced the oil pump with the ms123 pump and it made no difference, I didn't check bearing clearances while I was there as access was bad but I'm certain they are good, the whole engine is quiet as a whisper when cold with pressure, as said previously the bottom end would have to be rooted to get that low oil pressure. I have a new symptom also, the engine starts to miss when warm.

 

I'm pretty certain I've figured it out and it has NOTHING to do with the oil system. there are other symptoms as well - It has erratic idle and low idle although it seems normal to be around 1000 rpm range this is not really normal for my 5mge as it was much higher in my donor car and that's a low idle for 5mge's, also in relation to the idle the the later M series engines oil pumps are high volume low pressure so anywhere around 5 psi or higher would be normal at idle, so it doesn't surprise me it needs a bit of idle speed to push up the pressure.

 

Initially when I first fired up the engine I didn't pay any attention to the oil pressure when warm but I did notice it had really high idle (common for 5mge's, specifically old ones) I thought this was an ignition timing thing so I kept constantly screwing around with the ignition advance, little did I know it was running completely normal for a couple of hours, until the idle dropped which I thought must of been my timing adjustments but was actually just the head surface expanding a bit after some heat cycles :blinks:

 

 

Idle too low - low oil pressure - erratic idle within 100 rpm range - engine missing when warm - cooling system seems to be getting super pressurised (possibly oil in coolant) = blown head gasket :rant:

 

 

I had just put a recod head on and I used arp head studs from the 7mgte and spaced them higher with ball bearings but I F****ed something up when I torqued them I'm pretty sure and I used copper spray on the head gasket, don't know whether that would have anything to do with it. later M series engines are terrible! If I were to continue with an M series motor I would just use head bolts. Looks like there is now a 1JZ on my shopping list :yes:

 

Just thought I'd document this here so it might help someone out in the future.

 

Thanks for the help

Edited August 29, 2015 by ms85er

[altezzaclub]

Well,, that explains why it was such an odd problem! Aren't those M motors famous for BHGs, somethng about the factory toque figures were not high enough??

[ms85er]

Well,, that explains why it was such an odd problem! Aren't those M motors famous for BHGs, somethng about the factory toque figures were not high enough??

 

Yah the 7mge had its head gasket material changed just before production and they forgot to tell the factory to torque down the head an extra 20 or so ft lb, also their general head design tends to support hot spots, but not the 5mge its known for being reliable but sometimes temperamental, as such I have provided a perfect example of that above. I don't think I torqued the head down properly with the studs I use so I'll take that as my fault :bright:

Edited August 29, 2015 by ms85er