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Oil pressure warning light

6.6K views 11 replies 7 participants last post by  gerontius  
#1 ·
Hello guys,

i know this topic has been talked about a lot of times but I seem to have a rather special issue with this in my TT.
I've done all the things you may find on forums or internet to resolve this but still i get the warning light. So I'm
kinda desperate for another solution since this is quite irritating.

It's an 2000 year APX engine with 100000miles. First time I got the horrible red oil pressure warning I stopped the car and
towed it to the garage. Since car was not serviced properly with the past owners i wanted to replace every part that was related to oil pressure and do the full service on the car. On that service I've flushed the engine before doing anything else. Then i replaced all of these:

- Oil pump and the oil pickup tube
- Cleaned the sump
- Conrod bearings
- Turbo feed oil line
- Reconditioned the Turbocharger
- Oil pressure switch
- All PCV hoses (and i mean every last one) and replaced them with silicone replacements from Forge/Samco and similar
- PRV valve
- PCV Non-return valve on the T-junction
- Put in new Castrol Edge oil and filter
... the list goes on, but this is all regarding parts related possibly to oil pressure.

However with all those parts brand new I'm still getting the oil pressure warning light. It's driving me crazy... It only comes on at about 1500rpm when engine is hot (car is running at least 10min), but it never shows when car is cold. When rpms go 1800 or above the warning light goes away. It never shows on idiling if revs drop slowly so i don't know if that means anything. VCDS does not show any fault code in ECU. Engine runs smoothly with no weird noise whatsoever.

Does anybody have a suggestion what to look at to solve this ? Any other parts that could cause this ?

Could this be an electrical issue ? I've read a temperature sensor could cause it.... i did get an coolant red warning light a few times,but it never appeared again since then. Coolant is also new and level is up to specification in the tank.

Thanks
 
#3 ·
Did you buy genuine audi/vag oil pressure switch? If not replace as Hoggy says.

Seeing what you have spent so far I would be tempted to get an additional oil gauge and run in temporary through to cabin so you can confirm actual pressure.

Does a dash pod fault cause this?
 
#5 ·
Hello again,
i've checked the pressure sensor again, the dashpod and it all functions normally.

We even replaced the main crankshaft bearings and still the beep at 1500rpm when hot. The bearings were a bit scored, but the crankshaft is like new. In with the new bearings.

Measured oil pressure at hot idle was 11-12psi (or 0.8bar). How is this even possible with all the main parts in the oil system brand new ?

What can be the cause of this ? I don't have a clue...
 
#6 ·
You mentioned low coolant. I'm assuming there's no mixing of oil & coolant ?

I say this because looking at some images of the 1.8T engine, it looks like they use the oil cooler / coolant block that the oil filter screws onto - part of the oil filter mounting.

I do know that sometimes these blocks can allow coolant & oil to mix, which could also contribute, (I'm guessing here), to low oil pressure. The VW 1.9 diesels also use this part and failure is a known fault.

Just a thought as you've eliminated most of the usual things.
 
#7 ·
Actualy i forgot to write. I put in a new temperature sensor also, obviously that did not help either.

If it was mixing oil with coolant it would be visible like an milky emulsion in the coolant bottle.
 
#8 ·
Hi, Camshaft bearings can be the first to suffer if running on reduced oil pressure for long periods. Oil pressure can be above the oil pressure switch of 15psi but low enough to cause wear at top of engine. I wonder if you are losing oil pressure from top of engine. Oil pressure relief valve in oil filter bracket is another possibility.
Hoggy. :D
 
#9 ·
Did you use a vag oil pump? I bought an aftermarket one and found the endfloat was excessive when it was new whereas the 147000 mile vag used component in my engine had negligible end float so the old one stayed in.
Also did you renew the seal between the pick up pipe and the oil pump with a new vag component?
Note there is no provision for a seal between the oil pump discharge port and the block, iirc I put a bead of blue threadlock around the hole when I refitted the oil pump.
All these are very small potential leaks in isolation but in summation they can contribute quite a lot at tickover speed, especially the pump end float.
A couple of other places where high mileage may affect the seals (either O ring or normal gasket) is in the hydraulic chain tensioner internal oil seal, it's quite a fine O ring. The gasket that fits beneath this component may be leaking as well.
Finally did you check the piston oil spray pipes for security or breakage? These are right on the oil main and any extra leakage can affect the oil pressure at tickover.
You didn't mention if you checked the crankshaft thrust bearings for end float.
The only other component that may cause problems is, as hoggy indicated, the pressure relief valve, springs for which are not available but you can clean the plunger as it may be coked up. If you wish to renew the spring you have to replace the whole bracket.
 
#10 ·
ivekgt said:
Hello again,
i've checked the pressure sensor again, the dashpod and it all functions normally.

We even replaced the main crankshaft bearings and still the beep at 1500rpm when hot. The bearings were a bit scored, but the crankshaft is like new. In with the new bearings.

Measured oil pressure at hot idle was 11-12psi (or 0.8bar). How is this even possible with all the main parts in the oil system brand new ?

What can be the cause of this ? I don't have a clue...
Since you have an accurate measurement of oil pressure,you now know the engine/oil pressure system is worn out.
As suggested by Hoggy etc, just cos you replaced a sheetload of parts doesnt mean you have solved the problem and you are now wearing out the bits youve replaced :(

Like for example , if the journal bearings were so bad you felt you had to replace them,having a shiny good looking crank doesnt mean anything. The crank is the hard part ,the bearings are the soft bits.
On an audi 80 my journal bearings were fooked, crank itself didnt look too bad , but with ovality etc , I had to go to the next size up on bearings and get the crank reground.
Same engine ,the sohc was just about in limits for camshaft and camshaft bearings.If it hadnt been..new cyl head minimum cos no seperate bearings.. and so on etc.

Youve got no real oil pressure :( , youve replaced parts but pressure is still bad..investigate other components(which might have been worn out before you even got the car)
:(
 
#11 ·
I don't think anyone is trying to give you a hard time with this as clearly it must be a massive PITA and ÂŁÂŁshed loads but you didn't say what condition the oil pick up pipe and sump etc were in when you took them apart :?

If the engine has had years of neglect before you got it then as the others say even with a box full of new parts it may be beyond economical repair and that from me is saying something! Maybe you need to ask an engineering company to look at the head and as mentioned did you replace the thrust bearings on the crank as every time you press in the clutch these load up.