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View Full Version : bought a used built/stroked short block...low oil pressure light is on.



b5v6
10-22-2011, 08:14 AM
At idle my oil pressure gauge is somewhere between 3-8 psi (analog, who knows what the uncertainty is). As soon as the engine rev's above idle the oil pressure light comes on.

I don't think this is a sludge issue but I'm going to throw in a bottle of auto rx. I don't imagine someone with a built engine (previous owner) running something other than quality oil. Any thoughts on where to start troubleshooting this? What are potential causes? Is there anything I can do to start eliminating possibilities without pulling things apart?

Seerlah
10-22-2011, 08:26 AM
Hook up an oil pressure gauge and check your oil pressure that way. If your engine is making a strange noise (low oil pressure engines run like complete sh*t (I should know) you should be very cautious of having it actually run. It could just be a faulty oil pressure gauge. If the gauge shows you are actually having low oil pressure, then drop the pan and replace the pick up tube and the pump if you feel neccesary.

walky_talky20
10-22-2011, 08:38 AM
Since both the gauge and the pressure switch are confirming low pressure, it would be hard to believe that both are bad. It will probably be quite noisy at such low pressure. If you really think it is fine, start it 1 more time with a different oil pressure gauge attached. When cold you should see over well 50 psi at idle, when hot at least 20 psi at idle. In any case, don't run the engine any more until you get it figured out.

The reason the oil pressure warning does not alert until revved is because it is not active at idle. The pressure switch is a 23 psi switch or so. So there is an expectation it will not close at hot idle ("hot" based on coolant temp of 60C). So when "hot", the oil pressure warning system is only active over 1500 RPM. So if the car is hot idling and you pull the drain plug, it will *not* give any warning. It will just get noisy and lock up the engine after a bit.

b5v6
10-23-2011, 02:19 PM
what kind of damage have I probably done to the engine by letting it idle for a combined 2-3 hours thus far? This is my build so it only has a test pipe (no exhaust), couldn't really hear how noisy the engine was. Will idling with no oil pressure kill my turbo as well?

walky_talky20
10-24-2011, 07:22 AM
If it had some oil pressure and just idling, it is probably ok. A lot of engines only have like 5 psi at idle from the factory. You could pull the VC and remove one of the cam bearing caps. That is usually the first place to show damage. If there is milky gray material there, that's no good. I think with no oil, it could surely kill the turbo yes. But it would probably be fine with even just a little bit if it was just idling. I would proceed as if it's fine for now.

Wet0willy01
10-25-2011, 02:00 PM
what oil are you running? coated bearings?

Audi Skate Snow
10-25-2011, 03:01 PM
what oil are you running? coated bearings?

Was going to be my exact questions.

If you have coated bearings and you are running say 5w-30 the oil light will probably come on. Same thing happen to me after my 2 liter build. Threw in some 10w and never saw it again.

Seerlah
10-25-2011, 03:17 PM
^Never knew that happens. Same thing if it is just drop on rods using coated bearings (if the upped displacement played a role)?

Audi Skate Snow
10-25-2011, 03:24 PM
^Never knew that happens. Same thing if it is just drop on rods using coated bearings (if the upped displacement played a role)?

Displacement doesn't play a role. Just the coated bearings do not like the lower weight oil. It is mainly when it gets to full operating temp. Myself and many others have had this issue with the coated bearings... there are people who have not though.

JumboBlack1.8
10-25-2011, 06:24 PM
^^Yup....My freshly built stroker motor with coated rod and main bearings did NOT like the 5w30 oil I used for break in.....especially on hot days. Changed to 10w40 and never saw the oil pressure light again.

b5v6
10-26-2011, 05:03 AM
I think I used 5w-30 just to get it up and running. I'll drain and try some 10w-40, hopefully that is all it is.

Audi Skate Snow
10-26-2011, 08:03 AM
yep.. i use DINO OIL.. .usually 5w-30 castro but the coated bearings do not like it at all.. so after a quick 20-100 break in i switched to thicker oil.

S4NIK8
10-26-2011, 10:06 AM
had the same problem with my S4, when it was at full temp on hot days the idle oil pressure was just low enough to trip the light. Super annoying, switched to a thicker oil for the summer and no more light.

Crispy222
10-26-2011, 10:10 AM
Haven't had an issue with low oil pressure. Coated Mains +1 over, Coated Rods std sized. 300 mile on Castrol 5w30, the last 5000 miles on Motul 5w30. I see 18-20 psi fully warm at idle, 920 on the tach. Brand new oil pump/pick up. Hot tanked cleaned block.

Maybe the PO put in +1 oversized bearings when he should have used standard sized. Now the clearance is to large and its dumping oil pressure out. I've heard of it before.

Audi Skate Snow
10-26-2011, 10:17 AM
Haven't had an issue with low oil pressure. Coated Mains +1 over, Coated Rods std sized. 300 mile on Castrol 5w30, the last 5000 miles on Motul 5w30. I see 18-20 psi fully warm at idle, 920 on the tach. Brand new oil pump/pick up. Hot tanked cleaned block.

Maybe the PO put in +1 oversized bearings when he should have used standard sized. Now the clearance is to large and its dumping oil pressure out. I've heard of it before.

Yea there are people with coated that have not had the issue. Most that do have the issue have both coated mains and rods. Pretty common issue. Scares the shit out of you after a freshly built motor throws a low oil pressure light ahah.

My bearings are STD size.

b5v6
10-26-2011, 10:24 AM
...Scares the shit out of you after a freshly built motor throws a low oil pressure light ahah...

yes it does...

Wet0willy01
10-26-2011, 10:58 AM
x3 I was very worried

Aragorn
10-26-2011, 01:14 PM
Maybe the PO put in +1 oversized bearings when he should have used standard sized. Now the clearance is to large and its dumping oil pressure out. I've heard of it before.

+1 bearings and a stock crank would lock up solid.

You grind the crank smaller to use +1 bearings.

Crispy222
10-26-2011, 01:39 PM
+1 bearings and a stock crank would lock up solid.

You grind the crank smaller to use +1 bearings.

Oversized bearings would give more clearance. Undersized bearings on a ground crank, but that is rare.

Aragorn
10-26-2011, 02:47 PM
Never heard of oversize bearings, components tend to wear out, not get larger! Why would you want slacker bearings?!

I had the undersize issue recently when rebuilding a 06A for a friend. He'd purchased a used set of rods and pistons which were supplied with new bearings. Quite randomly they supplied undersize ones, and never thaught to mention it. Only got one rod installed and realised something was seriously wrong.

b5v6
10-28-2011, 05:29 PM
10W-40 had no affect, still low oil pressure.

Audi Skate Snow
10-28-2011, 06:16 PM
10W-40 had no affect, still low oil pressure.

so it happened right away after putting the motor in? Hopefully clearances were all within spec. Get a oil pressure gauge and check it... hopefully it is just a faulty sensor... double check and make sure the pressure sensor is plugged in well.

b5v6
10-28-2011, 07:15 PM
so it happened right away after putting the motor in? Hopefully clearances were all within spec. Get a oil pressure gauge and check it... hopefully it is just a faulty sensor... double check and make sure the pressure sensor is plugged in well.

I have an oil pressure gauge, needle barely comes up past 0.

b5v6
11-30-2011, 05:25 AM
Houston, we have oil pressure...

New oil pump installed, though I probably could have gotten away with just replacing the pickup screen.
http://i84.photobucket.com/albums/k23/turboavant/IMG_00571.jpg

walky_talky20
11-30-2011, 06:26 AM
Wow. That is nasty. Glad you got it taken care of.

This is why we drop the pan on every 1.8T motor we ever have out of a car. Even if it isn't causing problems now, you want to clean the screen whenever you get the opportunity. It is just too common for these to eventually clog up.

Seerlah
11-30-2011, 06:54 AM
WTF is that?


Houston, we have oil pressure...

New oil pump installed, though I probably could have gotten away with just replacing the pickup screen.
http://i84.photobucket.com/albums/k23/turboavant/IMG_00571.jpg

b5v6
11-30-2011, 10:03 AM
I feel like a fool for not pulling the oil pan while the engine was sitting in my basement, won't let that happen again. Not sure what the clog was, but it was slimey and thick.

redline380
11-30-2011, 10:40 AM
I feel like a fool for not pulling the oil pan while the engine was sitting in my basement, won't let that happen again. Not sure what the clog was, but it was slimey and thick.

there are a few things that are standard things to do to a motor when it is pulled out. oil seals, internal bearings, and an oil pump, among other things. these are the most critical engine parts. sounds like you found out the hard way

Audi Skate Snow
11-30-2011, 11:51 AM
wow! glad you fixed this problem!