David Jenkins
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| posted on 19/4/07 at 09:37 AM |
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Puzzled by oil warning light coming on
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?
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Mr Whippy
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| posted on 19/4/07 at 09:40 AM |
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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]
Fame is when your old car is plastered all over the internet
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David Jenkins
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| posted on 19/4/07 at 09:49 AM |
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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]
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trogdor
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| posted on 19/4/07 at 10:09 AM |
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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]
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Mr Whippy
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| posted on 19/4/07 at 10:17 AM |
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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.
Fame is when your old car is plastered all over the internet
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02GF74
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| posted on 19/4/07 at 10:51 AM |
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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]
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MikeRJ
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| posted on 19/4/07 at 10:56 AM |
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quote:
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)
It also increases oil temperature.
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Mr Whippy
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| posted on 19/4/07 at 11:00 AM |
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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]
Fame is when your old car is plastered all over the internet
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britishtrident
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| posted on 19/4/07 at 12:04 PM |
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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.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 19/4/07 at 12:15 PM |
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quote:
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]
Oil presure dosen't matter other than as symptom that the engine is already gone south --- a plain bearing is actually quite efficient at
drawing in oil and generating its own oil pressure by hydrodynamic action.
What a plain bearing really needs is oil flow at he correct temperature to cool it.
Better to spend money on an oil cooler with an oil thermostat and decent quality oil.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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David Jenkins
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| posted on 19/4/07 at 03:03 PM |
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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]
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iank
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| posted on 19/4/07 at 03:23 PM |
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quote:
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]
Yes, over cooling the oil is a bad idea, that's why you should fit an oil thermostat at the same time.
As for 101 opinions what size wheels do you consider best 
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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David Jenkins
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| posted on 19/4/07 at 05:42 PM |
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quote:
Originally posted by iank
As for 101 opinions what size wheels do you consider best
Oh do behave!
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02GF74
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| posted on 20/4/07 at 12:30 PM |
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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.
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David Jenkins
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| posted on 20/4/07 at 04:04 PM |
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quote:
Originally posted by 02GF74
wooah, how do you know the oil was cooked? did you measure its temperature?
Nope - purely guessing. I'm not going to take any drastic action at the moment - I'll wait and see if it happens again, and do some
checks at that time (it was getting quite dark last time). I am checking out the various options though, just in case (such as an oil cooler - see
elsewhere).
Prime suspect is the switch coming in unexpectedly, especially as the gauge was showing a decent pressure (the gauge does react quite quickly).
Checking the oil temp is a good idea - just another excuse for getting myself an IR spot meter! (I'm up to 3 reasons now - nearly convinced
myself).
BTW: What's 'normal oil temperature'?
cheers,
David
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Gaz 1977
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| posted on 20/4/07 at 06:47 PM |
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oil temp
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
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Peteff
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| posted on 20/4/07 at 07:57 PM |
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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]
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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David Jenkins
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| posted on 21/4/07 at 02:07 PM |
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quote:
Originally posted by Gaz 1977
I dont know why i know this but i believe it is between 78 and 90
Gaz,
I just zoomed over to your dad's place, and we measured 97 degrees off the side of the sump (using an IR temp sensor).
That was after a fairly 'lively' run...
David
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