Low Oil Pressure, Ish.

[hexhamstu 9]

I haven't done a hot oil test BUT the mechanical gauge behaved wildly differently to the dash gauge. It showed higher pressure for one, but also rose instantly with the revs whereas the dash gauge lagged and sometimes didnt really move at all.

[dcc 855]

I was with Stu when he mentioned his stop light was flickering, it was idling about 850rpm. Luckily I had some pliers so we turned up his idle to 1200rpm, the light stop flickering. I set his idle to what mine was roughly set at by Sandy.

 

I advised Stu that it is likely to be the sensor / switch or the wiring. Couldn't test it there and then but I can have a look tomorrow night Stu.

 

The only thing which cancerned me was the gauge was reading on the bottom mark, and with the revs so low at 800rpm, the light flickered. Something HAS to be working as it got far better when changed to a higher idle.

[hexhamstu 9]

If it stops raining I'll plumb the mechanical gauge back in and zip tie it under the bonnet. Can do a hot oil test then. any idea of a normal hot idle pressure?

[RossD 43]

The screenshot from Autodata earlier in this thread gives the pressure for 90 and 120 degrees.

[hexhamstu 9]

It doesn't give a 90 degree idle pressure. (but fair point I'll work off 1.8 bar)

Edited April 23, 2014 by hexhamstu

[RossD 43]

Yep, 1.8 - 2 bar pressure when hot is a healthy engine.

My french manual also says a drop of 0.4 bar from ideal pressures is acceptable for a worn engine, so really anything down to 1.4 - 1.6 bar at a hot idle.

[hexhamstu 9]

Bugger it, just bought a stack mechanical gauge and relevant adapter for m10x1.0. So will fit that next week along with new inlet manifold gasket. I'll just sack off the OE gauge for now, haven't bothered with a t-piece.

[hexhamstu 9]

Hahahaha.... Aren't 205s fun?

 

So went to fit the Stack gauge I bought. Started off by shearing the bonnet hinge bolt when I open the bonnet. GREAT START. Get the gauge fitted with no real issues. Start car up and set off to test oil pressure. Stop at petrol station, car won't start...... Bump start it down the hill and seems to start up OK. Then the accelerator gets caught on something and engine revs to limiter so have to turn ignition off. Turns out the pipe obviously stiffens with pressure and got in the way of the pedal. Go to start car again and guess what?!?! This time there's no hill. So got a mate to come with jump leads. Headed home as I was sick of the whole thing.

 

But the brief look I got I think the pressure was showing below 1.5 so possible is an issue. Will go buy some new oil and a filter and see what happens.

 

Need to add some ptfe tape to the threads on the oil pressure gauge as they were weeping slightly.

Edited April 29, 2014 by hexhamstu

[Edp 67 3 Cars]

Have you checked the pulley bolt for tightness? the oil pump works on friction so if its loose the pump won't be turning as fast as it should. I checked this out recently when replacing my oil pump as I have a low oil pressure problem on my mi16.

 

 

By the way what you just posted normally only happens to me! catalogue of errors

Edited May 2, 2014 by Edp

[hexhamstu 9]

I haven't had a torque wrench on it, but I did put a socket set on it and pushed it with my foot with the car in gear. I'll try jamming it at the fly wheel and have another go. Is it a breaker bar amount of torque?

[dcc 855]

If the bolt was loose you wouldn't get a consistent rise in oil pressure with revs (like you do) imho.

 

give us a call Stu to let me know your plans tonight / tomorrow.

[welshpug 1,622]

PUB!

[hexhamstu 9]

[hexhamstu 9]

New oil and filter. Good pressure when cold terrible when hot. Guess it's time to have a look at the oil pump.

Edited May 12, 2014 by hexhamstu

[mhyphenl 10 1 Cars]

I have this problem, great pressure when cold but on the bottom line when hot. Changed oil making sure it was 10w40 and stilll the same, rises well when revved but very low on tickover! I'm going with the idea that as long as there's pressure when driving and the light doesn't come on when idleing then we're ok!!

[hexhamstu 9]

I'm going to stick a higher pressure spring in there and check the oil pump while i'm at it. See if that magically solves my issue.

[Anthony 1,000]

What is the pressure showing with hot oil at idle (say 1000rpm)? The 1.5 bar on that picture on the last page is plenty good enough IMO if that's what it was showing.

 

Higher pressure spring won't do anything for low oil pressure at idle or low revs - it only comes into play once the pump is spinning fast enough that it's reached sufficient pressure.

 

Strip the pump down, check for any wear, clean out the pickup, check the relief valve, and if in any doubt, replace the whole pump with a known good OE one from a late XU10 engine.

 

As a cheat you could fit the drive cog and chain from an XU10 to spin the pump faster for a given rpm, thus generating more pressure, but personally I'd rather know why the pressure was lower than expected in the first place.

[dcc 855]

It was down between 0.5 and 1bar iirc

[hexhamstu 9]

What is the pressure showing with hot oil at idle (say 1000rpm)? The 1.5 bar on that picture on the last page is plenty good enough IMO if that's what it was showing.

 

Higher pressure spring won't do anything for low oil pressure at idle or low revs - it only comes into play once the pump is spinning fast enough that it's reached sufficient pressure.

 

Strip the pump down, check for any wear, clean out the pickup, check the relief valve, and if in any doubt, replace the whole pump with a known good OE one from a late XU10 engine.

 

As a cheat you could fit the drive cog and chain from an XU10 to spin the pump faster for a given rpm, thus generating more pressure, but personally I'd rather know why the pressure was lower than expected in the first place.

 

To fit an XU10 pump will I need the chain to go with it?

[DamirGTI 325]

Oil pump doesn't really "create pressure" , mainly it just shifts volume , thus i wouldn't waste time/money on replacing it cos doubt it to be the pump problem (unless it's blocked .. but guess that'll make low pressure all the time hot or cold) - it's the bottom end bearings to crank journal clearances (mains and big ends) where the actual oil pressure creates .. so i'd pop down the sump and have a look at the bearings .

 

But first check/measure the oil pressure with the proper manual gauge , as the OE gauge on the instrument cluster isn't so accurate .. though not massively inaccurate either from my experience but also they're accuracy do vary from one to another car .

 

Aside from pressure readings , when measuring , the gauge needle must be stable .. if it bounces around that'll mean that the pressure is leaking somewhere within the engine internals .

 

D

 

D

[Anthony 1,000]

The oil pump doesn't create pressure I agree and that was perhaps a poor choice of wording on my part, but if the pump is worn internally or the relief valve is leaking then it will have an impact on oil pressure.

[mhyphenl 10 1 Cars]

Spot on D, the newer springs we're just to up the relief pressure as the newer bearings had tighter tolerance. I think my issue is bearing wear but she runs really well at the mo. Might try a manual pressure guage but as I've got Air con etc etc I cant get to the damn guage without either removing the alternator and power steering or the inlet manifold etc.

[DamirGTI 325]

The oil pump doesn't create pressure I agree and that was perhaps a poor choice of wording on my part, but if the pump is worn internally or the relief valve is leaking then it will have an impact on oil pressure.

 

Ditto , agreed on that one .. it's a combination of the two actually - oil pump and bearing clearances , but the bottom end clearances (in fact all the moving metal parts within the engine) being the major part in creating oil pressure .

 

Not saying it could be a pump , but to me it seems more like a bearing issue (clearances getting bigger ..) .

 

D

[hexhamstu 9]

Would a bearing issue mean low oil pressure at idle only?

[welshpug 1,622]

It would mean lower pressure typically all through the revs and take more revs to get to peak pressure, IF it reaches it.