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Oil Pressure high - Please help - tuff one


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Hi Guys,

I have a problem with my 300tdi engine - 120k miles.

i have an aftermarket oil cooler and pipes which has worked fine for 2 years however now its building lots of pressure and blowing the ends off.

couple of points to note:

the oil cooler is not blocked

the pressure is high in both return and flow pipe

i have changed the oil filter

Any ideas why this is happening? - i dont have an oil pressure gauge but i know the flow never used to swell the pipes like that...there must be some reason why the pressure is higher...

Any ideas as im really stuck on this one.

thank you

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Without a gauge you don't know if the pressure _really_ is higher or if the swelling of the pipes is due to the hot oil having reacted with the rubber and caused it to soften.

The other possibility is a stuck oil-pressure relief valve in the pump.

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It's definitely higher as I replaced hoses . a pressure relief valve holds pressure with a spring so if all fails it should lose pressure not build right?

It can stick open, closed, or anywhere in between - very few things are good enough to only have one entirely predictable failure mode.

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Putting my thinking cap back on.

Have you tried removing the pipes to see what and which way the oil flows ? You said it was blowing the pipes off at the cooler. Are the pipes crimped or hose clip fitted ? I always use two clips to each pipe there.

If you check the oil flow. Then you can work through each pipe flow in turn to see if there's a blockage.

You did use a NEW cooler ? Never use a cooler from a blown engine as you can not clean all the bits out.

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Relief valve jammed shut surely.............

OR, is iit at all possible to reverse the connections and the pressure CLOSE the valve instead of opening it ?

Or the connections to an oilstat...............if fitted ?

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No, there is no way to put it together backwards. The oil pump is built around the nose of the crankshaft with the PSV off the bottom of the timing case.

I'm not sure how the 300TDI is all arranged, but normally...the oil from the pump then goes to the filter housing and through the filter and the cooler (or bypasses the cooler if the t.stat is closed) then into the engine. The normal pressure is set by the flow rate and the restrictions in the engine with the maximum set by the PSV. The PSV would normal only come into effect at low temperature or high engine speeds.

You need a pressure gauge on there to see what is happening. The book says 25 to 55 psi.

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