Oil light on when braking

[cliff.b]

Out for a nice drive this afternoon when I had to brake hard for traffic lights and noticed the oil light came on momentarily. Never noticed this before but don't usually get into a situation where I need to brake hard.

Tried it again on an empty road & same thing happened. Oil pressure gauge never dropped below 10lb but it seems to have a lag in it anyway so it may have been too quick to register.

Checked the oil level and about 3/4 full so wondering if this is not unusual or indicating a possible problem developing?

[johny]

I would get the oil level up to full and try again. If its oil starvation Ive never heard of it outside of racing...

[Pete Lewis]

being a 1500 spitty the oil pressure warning lamp is siamesed into the brake PDWA valve to test the brake warning light 

you may be seeing this lamp flash if the valve is operating due to some imbalance in the two brake hydraulic systems 

so it can be more brake related than engine oil pressure 

hence you used the brakes quite hard but no drop in the oil gauge  says this is brakes you have a problem with

Pete

[cliff.b]

5 minutes ago, Pete Lewis said:

being a 1500 spitty the oil pressure warning lamp is siamesed into the brake PDWA valve to test the brake warning light 

you may be seeing this lamp flash if the valve is operating due to some imbalance in the two brake hydraulic systems 

so it can be more brake related than engine oil pressure 

hence you used the brakes quite hard but no drop in the oil gauge  says this is brakes you have a problem with

Pete

Hmm, that's interesting and would be plausible however, I only have single circuit brakes. Should it be dual circuit on a 78 Spit?

[cliff.b]

9 minutes ago, johny said:

I would get the oil level up to full and try again. If its oil starvation Ive never heard of it outside of racing...

Yes, I've just filled it and will test again tomorrow. I was thinking the oil pickup is towards the rear of the sump and possibly if braking hard, some of the oil isn't. But maybe I'm deluding myself.

[Pete Lewis]

aha  single line   Hmmmm  

another idea would be to recalibrate./check the dipstick when you change the oil next time 

fill the specified amount less a 1 litre  , mark stick    as low   add the 1 ltr mark as High  

does it tally with what you have ???

wrong dipstick wont be the first time 

cant think of anything on the pump pick up that would cause a loss on wash slosh 

unless the pump body screws are coming loose and its sucking air when the level drops ???

whats the pressure like when running as normal ????

Pete

 

 

[cliff.b]

14 minutes ago, Pete Lewis said:

aha  single line   Hmmmm  

another idea would be to recalibrate./check the dipstick when you change the oil next time 

fill the specified amount less a 1 litre  , mark stick    as low   add the 1 ltr mark as High  

does it tally with what you have ???

wrong dipstick wont be the first time 

cant think of anything on the pump pick up that would cause a loss on wash slosh 

Pete

 

 

Yes, that's a good idea 👍

[Colin Lindsay]

Is it possible it's an electric issue ie the connection being broken on hard braking? 

[cliff.b]

27 minutes ago, Colin Lindsay said:

Is it possible it's an electric issue ie the connection being broken on hard braking? 

I thought about that but as far as I am aware, 12v is applied through the bulb to the oil switch which grounds  it, turning the light on.  When oil pressure breaks the switch the light goes out but any other break on the circuit would have the same effect.

Although I suppose if any part of the connection between the lamp and the pressure switch shorted to ground then that would light the lamp 🤔

And of course, I have recently had all my dashboard out to refurbish it. 

So it could possibly be a short on hard braking. 

[cliff.b]

1 hour ago, cliff.b said:

Hmm, that's interesting and would be plausible however, I only have single circuit brakes. Should it be dual circuit on a 78 Spit?

As far as I can see, the Spit got dual circuit braking from FH130000 in late 78, so my one just missed out.

[NonMember]

1 hour ago, cliff.b said:

when I had to brake hard for traffic lights and noticed the oil light came on momentarily.

Mine does that, too. Not always, and generally not when the oil level is above the maximum mark, but at 3/4 or below it will. I think it's because the pick-up is towards the rear of the sump and heavy braking can create enough slosh to expose it to air.

[cliff.b]

9 minutes ago, NonMember said:

Mine does that, too. Not always, and generally not when the oil level is above the maximum mark, but at 3/4 or below it will. I think it's because the pick-up is towards the rear of the sump and heavy braking can create enough slosh to expose it to air.

Ok, thanks for letting me know. That's either reassuring or possibly we both have something to worry about lol.

Will be interesting to see if it still does it tomorrow after topping the oil up.

[Pete Lewis]

is the oil level a bit low then ???  even down to the min mark it should cope with most driving situations

as anything between min and high is supposed to be ok , 

Pete

[cliff.b]

22 minutes ago, Pete Lewis said:

is the oil level a bit low then ???  even down to the min mark it should cope with most driving situations

as anything between min and high is supposed to be ok , 

Pete

It was at about 3/4 on the dipstick. If it doesn't do it after I topped it up then I assume it's not an electrical issue but it could be what you suggested, low level due to incorrect dipstick. 

[Pete Lewis]

i first came across dipstick problems with my Vit6  it let you overfill by over  litre 

th e 2000  is spot on     so its just a thought     add what it says see what the stick shows  

Pete

[cliff.b]

4 hours ago, Pete Lewis said:

i first came across dipstick problems with my Vit6  it let you overfill by over  litre 

th e 2000  is spot on     so its just a thought     add what it says see what the stick shows  

Pete

It still happened today after I had topped up the oil so I will definitely do as you suggest when I change it next. 

[RogerH]

Hi Cliff,

are you sure you do not have the oil level and brake lights swopped over !!!

 

Roger

[cliff.b]

51 minutes ago, RogerH said:

Hi Cliff,

are you sure you do not have the oil level and brake lights swopped over !!!

 

Roger

Do you mean the light that indicates a fault with the dual circuit brakes? If so my car doesn't have one as it has a single circuit. 

 

[Pete Lewis]

think i would disconnect the low press switch and do a brake test if it still lights you have a short in the warning harness somewhere 

Pete

[cliff.b]

2 hours ago, Pete Lewis said:

think i would disconnect the low press switch and do a brake test if it still lights you have a short in the warning harness somewhere 

Pete

Yes, that's a great idea. Why didn't I think of that 🤔

[PeteH]

Have you thought of swapping out the oil pressure switch?. It would (help) prove the switch itself was not the issue?. Not a common fault, but at least in theory it could be the issue, most have a spring internally which can degrade, and over time oil could byepass the plunger.

Pete

[cliff.b]

2 hours ago, PeteH said:

Have you thought of swapping out the oil pressure switch?. It would (help) prove the switch itself was not the issue?. Not a common fault, but at least in theory it could be the issue, most have a spring internally which can degrade, and over time oil could byepass the plunger.

Pete

Yes, I thought about that, although not sure why it would cause an issue when braking hard.

Another thing that has occurred to me is that I recently replaced my distributor which, amongst other things, has cured my erratic idling issue. Previously, I had tickover set at just above 1000RPM but now it is happy at 600.

So I'm wondering, as I am effectively making an emergency stop with the clutch depressed, the engine speed is dropping to 600RPM, with presumably reduced oil pump scavenging, while the car is still decelerating hard with possible significant oil "slosh". 

Any thoughts?

[Colin Lindsay]

14 minutes ago, cliff.b said:

So I'm wondering, as I am effectively making an emergency stop with the clutch depressed, the engine speed is dropping to 600RPM, with presumably reduced oil pump scavenging, while the car is still decelerating hard with possible significant oil "slosh". 

Any thoughts?

 

Are you really braking THAT hard all the time?

I'm just wondering, if the engine is dropping to 600rpm, then the oil pressure is seriously reduced - nothing to do with braking but that's coincidentally when it happens. Worn pump, worn bearings, the pressure drops as the engine revs drop and correspondingly the pump rotation. Can you replicate it with the engine at normal temperature, maybe after a fast run, and by dropping the revs right down when static?

[cliff.b]

15 minutes ago, Colin Lindsay said:

Are you really braking THAT hard all the time?

I'm just wondering, if the engine is dropping to 600rpm, then the oil pressure is seriously reduced - nothing to do with braking but that's coincidentally when it happens. Worn pump, worn bearings, the pressure drops as the engine revs drop and correspondingly the pump rotation. Can you replicate it with the engine at normal temperature, maybe after a fast run, and by dropping the revs right down when static?

No, I don't usually brake much at all but I have only seen the light come on when emergency braking from speed. I don't plan to do that on a regular basis (ideally not at all)

Also, as it is only for a second and when the engine is at low revs and no load, I doubt it is any more damaging than a cold start.

My only concern really is if it indicates something not right or the start of an issue so interested in people's thoughts and if others have seen the same thing.

 

[johny]

What pressures do you see on the gauge when hot at 2000rpm and tick over? I used to get the light flickering at low revs on hot days in traffic before replacing bearings/oil pump and improving cooling...