Ok the engine suffered a complete rebuild about 7000 km ago. Compression is right , no oil leaking , no oil burning but....

When I do 3 or 4 attempts in the same dune , the oil heats up and mi oil preassure light starts blinking.

What kind of oil are you using people I've tried different brands and Api designations always multigrade oil. Once I even used Castrol GTX 10w60 compleatly synthetic and nothing changed , maybe a motorcycle oil will do the trick? What about an oil cooler ?

Help me out here.
Thanks

Douglas

PD : excuse my english please.

It sounds like you might need some extra baffling in the sump. How steep and long are these dunes?

Rhinoman is right....need more info

How long are these dunes?
How much angle?
How high is the outside tempature?

Could be a combo of minor problems from you unique use...

Zag

The problem is not only when climbing steep dunes it's after a big effort , the other day I pulled mi friend's samurai (dead engine)out of the beach and some big bumps and after 3 miles the preassure light was compleatly on.

Any way the dunes are STEEP 42° about 100 meters long

I think you've got a bigger problem....

Get a mechanical guage on it and see whats happening to your oil pressure all the time.

When you did the engine did you replace the oil pump?

My opinion is....if it is doing it when on level ground after a hard pull it's generally one of 2
things
- Oil Pressure sender failing and sending a false signal
- Oil pump not creating enough pressure and volume

The reason I am assuming this is
- If it does it on level ground it's not a baffeling problem
- You've tried a series of good oils so it is unlikely the oil is breaking down and thinning out

That really only leaves the above causes.

Thats where installing a mechanical guage comes in
- If you do not show a pressure problem with the mechanical guage on it then it was the
  sender (if you got one just try another stock sender for a bit, but I would do the mechanical
  guage)
- If you do show a pressure problem with the mechanical guage youo KNOW you have to get
  it out and check the oil pump, pick up and passages.

Hope that helps

Zag

This sounds like what killed my first turbo,
low oil pressure, the problem was the relief
valve got stuck partly open and was blowing
off oil pressure all the time.

I'm afraid you are going to have to pull the
oil pump off and fix the stuck valve, or put
on a new pump, new pump is the best of coarse
but they also are about $100 here in the US

The problem is you are going to have to remove
the front axle to drop the pan, all this so it will not
leak oil after the repair, you might find it easier
to pull the engine out instead, even easier if you
have an engine hoist

Wild

Fuel in the oil......

the membrane in themechanical fuel pump ( you probably don't have sidekicks with that over there)  broke and started leaking into the the oil through th pin in the head.

The fix? electric fuel pump.
thanks to all

Electric is more reliable, good for you
Wild

Fuel in the oil......

the membrane in themechanical fuel pump ( you probably don't have sidekicks with that over there)  broke and started leaking into the the oil through th pin in the head.

The fix? electric fuel pump.
thanks to all

You may want to check your compression and overall "looseness" of things like crankshaft endplay.  The engine may not be as "peppy" as it used to be.  Fuel in the oil via the mechanical fuel pump can be very bad on an  engine! I have personal experience in this on my Samurai!  The 1.3 engine in it has a mechanical pump on the head that is driven by the camshaft -- probably the same engine/head that is in your truck.

I hope you caught this leak it before really bad things happened!

Fuel in the oil......

the membrane in themechanical fuel pump ( you probably don't have sidekicks with that over there)  broke and started leaking into the the oil through th pin in the head.

The fix? electric fuel pump.
thanks to all

We had them on the early models. Is yours a carb model?

Yes , mikuni carb on it , I checked compression in the cylinders and it indicated 165 lb with number 3 indicating 160 , need to check valve lash. What setting do you use for valve lash?
Last time I checked I set it up to 0.20 mm intake and exhaust. seem to work fine. A tighter setting works better but requires to much fuel and the prices are to high right now ( 1.10 us dollars a liter)
OUch!!