Oil light puzzle...

[rikvdub]

hey everyone, my 2001 slk 320 has a temperamental problem with the oil light? It lights up on and off every now and then........what’s causing this? Thanks Rik

 

[EmilysDad]

hopefully it's an iffy pressure switch, but it could actually be low oil pressure

 

[rikvdub]

hopefully it's an iffy pressure switch, but it could actually be low oil pressure

Fingers crossed it’s a dodgy switch!! Thanks for your response

 

[Botus]

is there any oil in the engine ?

people get very muddled over this light... its really very simple and basic.....

Light On = engine damage... because there is NO (or extremely low) oil pressure... the main driver of low pressure is because there NO oil in the engine for the pump to pressurise

therefore Light On = turn engine OFF straight away and resolve the cause before ever starting it again



the reason it matters, is if the warning system is functioning correctly (i.e. its correctly indicating low engine oil pressure) the lack of oil going through the pump will quickly damage the pump till its unable to provide adequate pressure.... and together with the limited oil capacity means the oil can't cool down enough to keep the engine in good shape.... the oil gets hotter, the engine gets dangerously hot in critical places (requiring higher lubricating properties than the right oil in the right quantity at the right temperature can provide) and what little oil is left soon collapses under the strain, resulting in no lubrication, no cooling and a large gap around the shell bearings.... which very shortly leads to total unrecoverable engine failure (without major expense …. usually much more than total engine replacement)

 

[EmilysDad]

is there any oil in the engine ?

.....

I used to work with a spark that used the low pressure warning as a low level warning ie when he went round a bend and the light came on due to lack of pressure ..... that's when he checked the level. No surprise that his car eventually suffered from upper end oil starvation problems.

 

[Uncle Benz]

Afaik there is no oil pressure warning light or oil pressure sensor on this engine. It has an oil level warning, but not a pressure warning. Mercedes are in their own field with this it seems.

 

[EmilysDad]

Afaik there is no oil pressure warning light or oil pressure sensor on this engine. It has an oil level warning, but not a pressure warning. Mercedes are in their own field with this it seems.

Surely all cars, whether they have a 3 point star or not, still have an oil pressure warning ....

 

[Uncle Benz]

Surely all cars, whether they have a 3 point star or not, still have an oil pressure warning ....

Nope

 

[EmilysDad]

Nope

I can't argue against as I don't know, but I don't agree

 

[rikvdub]

Ok so my light comes on after driving for about ten minutes but then goes off. It then keeps turning off and on several times randomly. I’ve checked the oil and it’s so clear I can’t tell if it’s low or not. I think I’ll change the oil and filter tomorrow and then I’ll know that it has the right amount. Is there a switch for the oil pressure or oil level that I could replace to se if either of these are faulty too? Thanks

 

[Larkone]

Wouldn't getting the data read that causes the light to come on be the best way to go? Anything else is just a guess = ££

 

[rikvdub]

Wouldn't getting the data read that causes the light to come on be the best way to go? Anything else is just a guess = ££

That’s a good idea, I wasn’t sure if running it through the diagnostics thy it would read an issue like this? I’m still going to change the oil today then I’ll go get the data read tomorrow. Fingers crossed it’s just a simple fix.

 

[LostKiwi]

Take a pic of the light you're talking about. They all come on when the ignition switched on before starting.

 

[ajlsl600]

if thats oil press light .check/change switch and fit a manual press guage and see what it says ! most come on at about o.7 bar and if that happens and the switch is ok its basically telling you to find another engine!!!!! because at 0.7 buxxer all is getting lubricated in any useful fashion. ! are we getting confussed with some ,check oil level light ? anyway if that was my eng . manual oil press test and oil filter biopsy ,all good there sweating over change oil/filter and press switch ,rock on .

 

[mattkh]

try reseating the oil filler cap.

 

[tttonyyy]

I used to work with a spark that used the low pressure warning as a low level warning ie when he went round a bend and the light came on due to lack of pressure ..... that's when he checked the level. No surprise that his car eventually suffered from upper end oil starvation problems.

I had a Pug 405 SRI like that when I was younger. Paid 300 quid for it because the starter was broken and the seller lived at the top of a hill so it could be bump started to get it home.

Anyway, it used to burn oil because the valve stems weren't meant for unleaded. Could tell when the oil needed topping up because cornering to the opposite side of where the oil pickup was would put the oil light on and the engine would rattle a bit more loudly until you got it straight again. Never seemed to cause it any harm, but then it only lasted a couple of years until I broke the diff pulling away a bit violently. Put a diff tooth clean through the diff housing.

But back to oil lights, certainly it is possible that it is the sensor. Some GM engines are known for it.

The other possibility is the oil - if it's low quality could it have broken down into a thinner oil which may result in lower pressure from the oil pump (may leak past closely machined surfaces of a gear pump more easily).

Does it do it from cold or only when the oil is hot? Any change to engine noise?

Does the light go out again when (gently) revved?

The other issue could be sludge on the pickup mesh blocking the intake. Only dropping the sump would show that though.

 

[rikvdub]

Thanks to all of you for your help and advice. But I’ve finally found the fault and got the issue resolved!

It was the oil level sender that is positioned in under the lower sump. Unfortunately it came at a cost of £155 inc vat from MB, but it was well worth it as I had all kinds of nightmares over this, thinking it could well be in need of a new engine. But thankfully it isn’t and I can relax and get back to enjoying it. Again thank you all

 

[Uncle Benz]

Nice result, well done!

 

[ernieh]

Thanks to all of you for your help and advice. But I’ve finally found the fault and got the issue resolved!

It was the oil level sender that is positioned in under the lower sump. Unfortunately it came at a cost of £155 inc vat from MB, but it was well worth it as I had all kinds of nightmares over this, thinking it could well be in need of a new engine. But thankfully it isn’t and I can relax and get back to enjoying it. Again thank you all

so...it was a level sensor and not a pressure sensor. I had 2 of them replaced on my 203 petrol because at that time they were prone to leakage.

Wonder why MB don't have pressure sensors?

Ernie

 

[rikvdub]

so...it was a level sensor and not a pressure sensor. I had 2 of them replaced on my 203 petrol because at that time they were prone to leakage.

Wonder why MB don't have pressure sensors?

Ernie

Yes mate. I asked the guy this question and he couldn’t answer me. But I still don’t understand why they didn’t fit this??