ianr
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| posted on 23/5/06 at 08:52 PM |
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Low Oil Pressure.
I have a 1700 crossflow and when the engine is warm and the car is idle the oil light flickers on. When the engine revs the light goes out till idle
again. I have just changed the oil pump and replace gaskets.
And have been told that this may be something to do with wear inside block itself, this to me sounds a expensive  .
Is this the likely candidate or should i be looking elsewhere first.
I do have an oil pressure gauge but the adapter is split , so until i source this i cannot see what the pressure is.
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David Jenkins
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| posted on 23/5/06 at 09:00 PM |
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I'm afraid that the only real diagnostic tool is the pressure gauge - until you know for certain what the pressure is you can't make a
decision.
Could you put the gauge connector in place of the pressure switch, just for a few minutes? At least you'll know what's what.
David
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Johnmor
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| posted on 23/5/06 at 09:50 PM |
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Low oil pressure
I dont want to be the bearer of bad news , but it is a good possibility that its caused by excesive wear on the bearings.
As the wear increases the space between the bearing face and the crankshaft increases and therefore the pump can not maintain the pressure required to
provide an effective lubricated surface.
You could try a heavier viscosity of oil but thats is just putting of the inevitable and won't do the rest of the engine any good.
When you replaced the oil pump, did you check the clearence between the impellar and the base of the pump, this is critical in determining the oil
pressure and usually needs feeler gauges to ensure the pump is correct.
Just a thought.
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stevebubs
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| posted on 23/5/06 at 10:20 PM |
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What oil are you using? Modern Magnatec etc isn't ideal for a crossflow. I tried both GTX and Shell Helix, both for conventional engines, and
both were too thin when warm.
Ended up with a big drum of cheap oil from CostCo. Big plastic Drum was cheaper than 4l of either of the above and all problems went away.
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ianr
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| posted on 23/5/06 at 10:25 PM |
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quote:
Originally posted by stevebubs
What oil are you using? Modern Magnatec etc isn't ideal for a crossflow. I tried both GTX and Shell Helix, both for conventional engines, and
both were too thin when warm.
Ended up with a big drum of cheap oil from CostCo. Big plastic Drum was cheaper than 4l of either of the above and all problems went away.
5/40 from memory, Halfords own.
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nitram38
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| posted on 23/5/06 at 10:44 PM |
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Worth checking, but doesn't this pump contain a pressure relief valve controlled by a spring?
If it does, try changing it.
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stevebubs
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| posted on 24/5/06 at 12:05 AM |
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quote:
Originally posted by nitram38
Worth checking, but doesn't this pump contain a pressure relief valve controlled by a spring?
If it does, try changing it.
Yes, it does.
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David Jenkins
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| posted on 24/5/06 at 07:14 AM |
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quote:
Originally posted by ianr
5/40 from memory, Halfords own.
Many x-flow users prefer 20W/50, which is what was originally specified when the motor was new, back in the Middle Ages.
The Haynes Book of Lies suggests 10W/40 I believe, but even that seems light to me.
cheers,
David
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britishtrident
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| posted on 24/5/06 at 07:18 AM |
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Oil pressure switches fail with age, they are also available in different pressure ratings. -- as DJ pointed out the only real check is to screw in a
proper bourdon or other mechanical type gauge.
Most likely cause if not the switch is big end bearing wear, in a Locost it should be possible to change the big end bearing shells without removing
the engine, only tricky bit is dealing with the sump gasket end seal and bolts at the flywheel end.
When the sump is off take the oppertunity to clean the oil suction strainer as restricted flow at this point is a frequent cause of reduced oil
pressure.
Falling oil pressure is only a symptom --- oil pump output pressure in itself dosen't matter its the flow of oil to the bearing that matters,
the bearing generates its own much higher oil pressure internally but it needs sufficient oil flow to generate this pressure and cool the bearing.
Don't get side tracked by oil grades when hot a 5w/40 has the same viscoscity as 15w/40, using a 20w/50 in an Xflo will make it much more
difficult to start in cold weather.
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Macbeast
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| posted on 24/5/06 at 09:08 AM |
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I had exactly this years ago on a BMC A-series engine. I tried all the quick fixes and of course they didn't work. Eventually accepted the
inevitable and got recon crankshaft, main and big end bearings which was what I should have done in the first place.
I guess if you can hear a muted rumble at idle from inside the engine (not the exhaust note ) that would confirm big end bearings are worn.
[Edited on 24/5/06 by Macbeast]
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David Jenkins
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| posted on 24/5/06 at 09:12 AM |
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quote:
Originally posted by britishtrident
Don't get side tracked by oil grades when hot a 5w/40 has the same viscoscity as 15w/40, using a 20w/50 in an Xflo will make it much more
difficult to start in cold weather.
Get a bigger battery!   
David
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ianr
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| posted on 24/5/06 at 11:13 AM |
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quote:
I guess if you can hear a muted rumble at idle from inside the engine (not the exhaust note ) that would confirm big end bearings are worn.
Cannot hear any rumble or knocking from engine
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Macbeast
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| posted on 24/5/06 at 02:20 PM |
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Well there's hope maybe
Really, only sure thing, as has been said, is get a pressure gauge onto it.
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britishtrident
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| posted on 25/5/06 at 05:12 PM |
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quote:
Originally posted by ianr
quote:
I guess if you can hear a muted rumble at idle from inside the engine (not the exhaust note ) that would confirm big end bearings are worn.
Cannot hear any rumble or knocking from engine
The signs are you have bearing wear rather than the bearings having run, do it now and you might gat away without a crank regrind for few years at
least.
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02GF74
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| posted on 26/5/06 at 01:42 PM |
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quote:
Originally posted by britishtrident
Falling oil pressure is only a symptom --- oil pump output pressure in itself dosen't matter its the flow of oil to the bearing that matters,
the bearing generates its own much higher oil pressure internally but it needs sufficient oil flow to generate this pressure and cool the bearing.
quote:
Originally posted by Johnmor
As the wear increases the space between the bearing face and the crankshaft increases and therefore the pump can not maintain the pressure required to
provide an effective lubricated surface.
some interesting points.
The pump produces flow not pressure, that is produced by the resistance to the flow, in this case the crankshaft and other bearings.
If you don't believe me, trying blowing air out of you mouth, then repeat blwoing into a ballooon. In the second case the flow of air coud be
the same but it becomes hard to blow due to the "resistance" offered by the ballon - you are working against pressure.
That is what the oil pump is doing; there is a relief valve to prevent the presure going to high.
Interesting second point ^^^ about the flow; that would mean that once the oil pressure lamp is low, the engine should still keep going on, whcih I
believe it does, eventually the bearing disintegrates or something breaks big time; having lower presure means the oil won;t be squirted as far, say
to cool piston undersides.
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Marcus
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| posted on 30/5/06 at 08:12 AM |
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I use Halfords Classic 20 / 50 oil. Looks and smells like original Duckhams. My oil pressure runs at about 20psi when hot - right on the limit of the
switch - and has had new bearings 10k miles ago.
Marcus
Marcus
Because kits are for girls!!
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