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Oil pressure drop under load and right hand turn 351C

12K views 25 replies 9 participants last post by  xrgt 
#1 ·
Guys, I hope some brainstoriming on this one will help...

1. 2 wiped lobes on previous hyd cam, both lifters in bad condition, bores OK.
2. ran in new cam/lifters with over 50psi - no problems.
3. changed oil and oil filter with filtermag - 20W50
4. re-adjusted valve lash per cam spec Comp Cams 270S.
5. Idiot proof mechanical oil pressure gauge - Autometer.

Oil pressures stationary and during test drive

-80psi cold idle
-35psi-40psi hot idle

I noticed, the pressure drops to 0 !! when turning right, regardless off engine speed!!, and then when you straighten up pressure returns to normal 40 - 80psi depending on engine speed. This does not happen when turning left ??

Also straight acceleration causes the pressure to drop to 0 for a few seconds and then jumps back up to normal regardless of engine speed ??

I had to drop the sump during the cam swap ... DO NOT ASK WHY! and noticed the pickup screen was bent, probably due to clearance issues with the sump/crossmember. I did not replace it as oil pressure was fine before the cam swap.

I have refrained from driving it until I fix this problem...

Any ideas?

Thanks
 
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#2 ·
low oil or your doing high rpm with a stock sump. The pickups on the left side of the sump.

[edit]If the oil pressures too high you'll also activate the relief valve. So pressure will drop but not to "0".

Brenden
 
#3 ·
Brenx,

5lt of oil with new filter and stock sump, i think should be OK??

still drops on right hand turns only regardless of low/high rpm...

Its got me spooked
 
#4 ·
Should be fine. You stated it drops under straight line accel. You may also find that your oil pumps toast. So unfortunately you may need to remove the sump again. If it dropped when your doing a steady rpm and at ie 60->100kph? I'd be looking @ a pump replacement. It's too easy to loose an engine due to a oil pump failure.

I find it's easier and faster to remove the engine. More room = less mistakes.

Brenden
 
#5 ·
I've never replaced a pump/pickup/driveshaft...

Apart from raising engine to drop sump, is there anything else i need to know.

Tonez.
 
#9 ·
I had the same problem on my car.

Checked the gauges, tried different oil filters and oils and even drove around with a mechanical gauge sticking out of the shaker hole in the bonnet so that I could see the PSI reading.

It ended up being a stuffed Oil pump.

I replaced the pump with the engine still in the car............on a hoist.
It was easy enough to do. Engine mounts were undone and a screw pole was placed under the transmission housing and the whole assembly was lifted slightly to ensure clearance for the sump to slide out.

I replaced the old Hi Volume pump with a new Standard Volume unit and a Hi Energy anti cavitation pick up. This new pick up is smaller so the Hi Energy Sump I have slid on a lot easier.

I haven't had any issues since.........................but bloody hell did it take a while to diagnose the problem.......... :AAHHH:
 
#10 ·
ESP, i am about to try and remove the sump with the motor in the XD. I am hoping i have a brand new "dud" oilpump. I have a 7 litre High Energy sump and was wondering how hard it is to remove while motor is still in. I was just going to live the with low oilpressure, but when hot and doing a bit over 100kmh, 2 different mechanical gauges start flickering from 50 to 40 and back to 50 and with a bit more pedal, it gets even more erratic. (I hope its the pump).
 
#12 ·
Could be the pickup loose in the thread into the pump housing.

Trying to think whether it would swing loose more on right hand corners and sucking air.

It definetly got enough oil? And the gauge is right?

That oil pressure sounds bloody high!
 
#13 ·
(It is possible to totally remove a stock sump with motor still in car. You remove engine mount bolts (ie long ones, one per side), lift motor a few inches and then reinstall the bolts. The motor then sits higher as the bolts are sitting on the chassis mounts rather than through them. Next remove all sump bolts, lower sump slightly and then use spanner to remove the two oil pump bolts. The sump with oil pump in it can then be wiggled out. Memory dictates the sway bar may need to be dropped. If you do this just dont forget the oil pump drive shaft when doing the reverse assembly.)

Could it be explained be the g forces shorting/affecting the sender unit?

The only other issues I can think off is pickup not loctited into pump and has spun and therefore sucks air under acceleration/side loads. Other is pan to pickup clearance causing starvation, ie how did pickup get bent?
 
#16 ·
xdclevo said:
ESP, i am about to try and remove the sump with the motor in the XD. I am hoping i have a brand new "dud" oilpump. I have a 7 litre High Energy sump and was wondering how hard it is to remove while motor is still in. I was just going to live the with low oilpressure, but when hot and doing a bit over 100kmh, 2 different mechanical gauges start flickering from 50 to 40 and back to 50 and with a bit more pedal, it gets even more erratic. (I hope its the pump).

With the car on a hoist it is not that difficult. We did it with minimal fuss and frustration. As per Silicon's post, you only need to raise the engine/transmission assembly an inch or so. This will give you enough room to undo the pump bolts after you drop the pan first. Just make sure you remember which way the pump shaft goes back in on reinstallation as there is a circlip on one end. We were scratching our heads for a while before we realised which end was correct.

It may also pay you to go the Hi Energy anti cavitation pick up while you're at it. This will definitley make re installation a lot easier as you can remount the pump and pick up and then slide the sump back on. If you use the old pick up, you'll have to place the pump and pick up in the sump and place the whole assembly back on and then tighten the pump screws. This is a BITCH of a job as you are constantly trying to avoid gasket sealer and gasket. The High energy anti cav pick up is much smaller so it will allow for separate installation................................THE WAY TO GO.

Good Luck...........let us know how you go.
 
#17 ·
xrgt said:
Guys,
I noticed, the pressure drops to 0 !! when turning right, regardless off engine speed!!, and then when you straighten up pressure returns to normal 40 - 80psi depending on engine speed. This does not happen when turning left ??
xrgt, have you found anything yet. I just went and fueled up the XD and tested a few things. When driving along with 40-50 pounds pressure, any turn left or right, it drops to 20 pounds then strait back to 40 odd. It does it slightly on acelleration, but if doing 100 kmh, and a stab the brakes even just slightly, the pressure drops to 20 again, then strait back to 45-50. I am still thinking pump problem, or pickup being too close to the sump floor.
 
#18 ·
xdclevo said:
xrgt, have you found anything yet. I just went and fueled up the XD and tested a few things. When driving along with 40-50 pounds pressure, any turn left or right, it drops to 20 pounds then strait back to 40 odd. It does it slightly on acelleration, but if doing 100 kmh, and a stab the brakes even just slightly, the pressure drops to 20 again, then strait back to 45-50. I am still thinking pump problem, or pickup being too close to the sump floor.

Mate

It'll be the pump, you can bet on it. It's exactly what happened to me.
It's the most bizarre thing................when you tell people they just stare at you like you're a terrorist. Even my engine builder who's been living and breathing Clevos for 20 years kinda looked at me strange. "You get low pressure when you turn right only and when you brake even slightly in a straight line..............????..............Hmmmmmmmm.......You okay son !!! "

When we pulled the pump out, we found it to be grossly scored on the inside. The clearances were totalled and it was having difficulties sucking anything in except for air. It was an amazing transformation when the new pump was put in. The car was quieter, it idled heaps better and I also got slightly better economy by ditching the Hi Volume pump.

It just sound too similar to my situation to be anything else.
 
#19 ·
got the parts from Rocket today... and will be installing on the weekend..

do i need to worry about pickup to pan clearance ?
 
#20 ·
You say that the screen on the pick up was pushed up last time you pulled the sump off, could it be that the pick up tube has been bent / cracked?
Or as mentioned by someone else, maybe the pick up tube has come loose in the pump, therefore leaking air in around the thread when oil surges away from the pump.
 
#26 ·
could have been both pump and pickup... pickup was physically bent, so was not sitting in the correct spot. Its a tapered thread to the pump so i'm sure it was not sucking in air... still can't explain why it only dropped on right hand turns though?

I'd suggest you replace both.

I just got back from WSID!!! time slips... see next thread...
 
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