V8 County oil temperature rising

[V8Johnno]

I changed the oil cooler hoses on my 3.9 110 V8 County............
normally the water temp sits on 80ish 'c and the oil sits around about the same. It has no pulley fan, only a set of two cowled fans off a Ford.....
Normally (last 4 years) I can drive it up to and at highway speeds and generally around town with no fans on, only needing to put them on for long traffic light stops etc...and both the oil and water remain below 82'c for most driving
With the new oil cooler hoses, there were no probs whe driving it round town......but as son as I started driving up the highway the oil temp started to rise. the water temp started to rise too, and putting the thermo's on dropped the water temp back down to normal, but the oil temp continued to rise. I do not think it is a gauge problem as the oil pressure was dropping, the higher the oil temp rose.

So once I checked the hoses weren't blocked and thus no improvement, I removed the oil cooler which also wasn't blocked.
So I thought id take it for a run with no oil cooler and within 5 k's of 60-80kph driving , the oil temp rose close to 100'c..............
So the oil cooler is working as without one it gets hotter faster... the problem is the oil temp is rising no matter what.............its not using coolant and the rad is full, the water pump is only about 20,000k's old...... I am puzzled as the performance is spot on.............any ideas or thoughts??????
It has a four core radiator which is reasonably new and unblocked.
I think the temp is rising in both water and oil but the thermo fans are keeping only the water temp down. Alas not the oil.
Normally a good ten minute thrashing in the sand and a few dune attempts would get the oil temp up five degrees, but once back to progressing normally, the oil temp would be down to normal within a k. unfortunately now not the case. Im wondering if its completely unrelated to changing the hoses and has just done something at the same time just to confuse me (as landrovers sometimes do)

cheers
V8Johnno

[superquag]

Why did you need to change the hoses ? - Possible to put them back to test the theory ?

[Tank]

Is the oil cooler in the Radiator like the Disco's, or does the County have an oil cooler outside of the radiator? Regards Frank.

[V8Johnno]

I changed the hoses because they were a bit sun faded and slightly perished where they had a little hose exposed on the top of the bullbar
the oil cooler is in the bullbar..............
the new hoses are identical to the old ones so changing them shouldn't do anything, but ill try

[Tank]

Have you some pics, Regards Frank.

[chazza]

What about checking the temperature of the sump and oil-cooler with an infra-red thermometer and see if it really is getting too hot?

However; given that you noticed a pressure drop at the same time as over-heating, it makes sense that you are correct, but by checking both it will at least eliminate the temp. sender and gauge.

The only other thing I can think of is a partially blocked cooler core on the outside - blow it clean with compressed air. How old is the oil? Does it need changing?

Cheers Charlie

[V8Johnno]

Im pretty confident the gauge and sender are good as everything behaves normally until I attempt highway driving The oil pressure is behaving as if the oil were getting hot and dropping within the bounds of what it normally does when the oil is hot ie sand dune attempts etc.. The oil is not very old at all, barely a thousand K. The oil cooler was reasonably mostly clean between the fins, but is now spectacularly clean. I have dismantled and removed the oil pump and cooler and pipes. Once a new oil pump gasket arrives I will re-assemble it all and change the oil. I might have someone take a tank off the radiator and see if there is an untimely blockage of some sort

[chazza]

It may be the case that something is blocking inside the oil cooler pipes such as bits of silastic.

Try taking it off and pouring de-greaser through it and blow some compressed air through it after it has been rinsed in water. You could check the flow by passing water through it with the garden hose,

Cheers Charlie

[V8Johnno]

Thanks for all the ideas guys.
It turned out the new oil cooler pipes were defective and collapsing internally, but only when heat was added to the equation.

Upon running the hosepipe through the cooler hoses the flow was very good, with cold water.
However, flow was more reduced, the hotter the water being passed through them. I ended up cutting the hoses open along their length to find out what was going on and there was a suspect area which, when put in heated water, was delaminating (separating) where the string braid was.......
The net result of me rebuilding the oil pump, new cooler hoses ( full refund from the shop) and getting the radiator core unblocked (about 5% blocked) the county now runs cooler with higher oil pressure than its ever had and nice cool correct temp oil.....thus I am a happy county driver once more..........

cheers guys

V8Johnno

[chazza]

Well done Johnno for persevering and finding the most irritating of all faults - the new part that is crook!

Cheers Charlie