Went out for a nice long drive yesterday evening. Everything running well, but after a long fast drive home (about 20 miles dual-carriageway at 70mph) the oil warning light flashed a few times when the engine went down to tick-over speed. What puzzled me is that the oil pressure gauge was still showing around 40 psi. Took the car out for a blast this morning to get it well warmed up, and everything worked as it should.

I can only think of 3 possible reasons:

1. The oil pressure switch is faulty, maybe when it gets really hot. It's a ~20psi switch, rather than the 'your engine has just trashed itself' standard type.
2. The oil pressure gauge is lying - but I don't think it is, as generally it does show me expected values (60 - 75 psi when the engine is working, 40-ish on tick-over - it's a high-pressure pump).
3. The oil's getting too hot and causing odd effects.

BTW: It's a 1660cc crossflow, mildly tuned. The oil and filter were changed a couple of hundred miles ago, the oil level is correct and the oil is clean.

Any clues or suggestions?

switch sounds knackered.

Glad someone else runs will such high oil pressures, I always felt that my pinto was a bit ott in that department.

My cologne v6 is just the opposite even when I fitted a high pressure pump. Had me real worried but when I ask a good engine shop I was told all was normal. Stupid question but should I have changed the spring in the oil pressure relief valve for a stronger one?

[Edited on 19/4/07 by Mr Whippy]

My oil pump was advertised as a 65psi one. When first fitted the engine was at the tight end of the normal range, and the gauge showed 80psi! It has settled down to where it should be these days, as the engine has run in.

Can't comment on a Cologne - the Xflow pump has the pressure relief valve in the pump casing, and fitting a higher-strength spring on the valve is what makes it a high-pressure pump.




[Edited on 19/4/07 by David Jenkins]

thats how you increase the oil pressure with the V4 tanus so i would imagine fitting a stronger spring would work for a v6 cologne



[Edited on 19/4/07 by trogdor]

cheers, I'll have to have a look where the damn spring is as I had assumed it was in the pump housing, but perhaps not. I also think the high pressure pumps are the ones with the best tolerances but don't quote me on that. One issue that is on my mind is the pump drive shaft, on both engines it is just a hex bar like an Allen key which is driven by the dizzy. Just how strong is that thing??? I had considered replacing the standard ones with very good quality cut down Allen keys as I'm worried that I might strip them and loose oil pressure.

I would say nothing to worry about and my money on the switch telling the truth due to oil becoming thinner when warmed.

What sort of time response is the guage? Is it electrical or mechanical? I would expect there is some delay/damping built in and the switch is responding faster. (or less likley a loose wire?)

If you had fitted the proper oil pressure switch - 2 psi - you would have no worries

Incidentally, crossflow oil pump valve spring sits behind what looks like a small core plug that has been staked right? I assume you took the plug out, fitted new one, and restaked it in place?

A common trick to increase the oil presure spring is to fit spaces such as a metal disc or a bolt between the spring and inside the valve thimble.

... and what is the obsession about increased oil pressure? It is oil flow volume that is more important, a higher pressure saps engine power and accelerates wear in the oil pump. (but not to an extent that you should have sleepless nights)

[Edited on 19/4/07 by 02GF74]

quote:

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Originally posted by 02GF74
... and what is the obsession about increased oil pressure? It is oil flow volume that is more importat, a higher pressure spas engine power and accelerates wear in the oil pump. (but not to an extent that you should have sleepless nights)

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hmm my oil gauge takes less than a second to cover the scale.

pumps only £80 don't care if it wears out. I like the higher pressure cos if I get the oil real hot it still won't drop to low.

I have a cooler.

[Edited on 19/4/07 by Mr Whippy]

Yup, HP oil pumps for Xflos are snake oil, that have the side effect of making starting in wintery weather much more hit or miss.

When the engine is warm and fully run-in what determines the oil pressure is the bearing clearances oil temperature and grade.

quote:

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Originally posted by Mr Whippy
hmm my oil gauge takes less than a second to cover the scale.

pumps only £80 don't care if it wears out. I like the higher pressure cos if I get the oil real hot it still won't drop to low.

I have a cooler.

[Edited on 19/4/07 by Mr Whippy]

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re: High pressure pump

I rebuilt my crossflow using Wallage's book as a guide - he said that a high-pressure pump is the best option, so I did as I was told!

The pump was bought from Burtons as a high-pressure jobbie - I haven't modified it.

Normally I don't have a problem with the oil warning light - I was just wondering why it chose to come up this time.

Regarding the oil cooler - I'm sure that someone on this forum said that over-cooling the oil is a bad thing. Although I was running at a fair speed for quite some time, it was a bl**dy cold evening, so I wouldn't have expected the oil to cook.

Just goes to show - ask anything here and you'll get 101 conflicting answers!


David

[Edited on 19/4/07 by David Jenkins]

quote:

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Originally posted by David Jenkins
...
Regarding the oil cooler - I'm sure that someone on this forum said that over-cooling the oil is a bad thing. Although I was running at a fair speed for quite some time, it was a bl**dy cold evening, so I wouldn't have expected the oil to cook.

Just goes to show - ask anything here and you'll get 101 conflicting answers!


David

[Edited on 19/4/07 by David Jenkins]

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quote:

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Originally posted by iank
As for 101 opinions what size wheels do you consider best

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wooah, how do you know the oil was cooked? did you measure its temperature? as far as you know, maybe it is running at correct temperature and the pressure switch is kicking in becasue it has thinned out to it proper consistency? the engine having been run in, (as somebody said accounts for most of the resistance to oil flow) is not longer creating the smae resistance you had earlie - the high psi switch isn;t helping ya either.

before fitting oil cooler, try to measure oil temp.

If you can gain access to an IR thermometer*, then measuring sump temp would be a good indication - you can buy these one time LCD temp strips cheaply (usually for measuring brake temp).

* I have one I could lend you but you are too far away.

quote:

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Originally posted by 02GF74
wooah, how do you know the oil was cooked? did you measure its temperature?

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I dont know why i know this but i believe it is between 78 and 90

I am sure you will get it sorted.

GAZ

I had a crossflow Escort Estate when they were still common and it always flickered the oil light on tickover after about 50 miles even after an oil change and a new sender. It did it for 4 years with no consequences, try speeding the tickover up if it worries you .

[Edited on 20/4/07 by Peteff]

quote:

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Originally posted by Gaz 1977
I dont know why i know this but i believe it is between 78 and 90

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