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Oil Leaks... Again

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BLACK'98DSM

5+ Year Contributor
4,450
1,889
Feb 9, 2019
Alabama
I've already fixed 5 oil leaks since I bought the car. Last week there was another spot in the driveway... I already replaced crankshaft seal, valve cover seal, camshaft position seal, oil filter, and a couple others I can't think of off the top of my head. I've tried degreasing and idling for minutes to hours to see where the oil comes from, but it only seems to leak out when I drive it and have pressure on the engine. By the time I get home to check it, there is oil everywhere making it impossible to see where it came from. It is a very small and minor leak, but its nasty and annoying. My only 2 thoughts is that it could be the oil pump or the main seal, both of which are hard to replace. I'm tired of diagnosing this engine so your thoughts are greatly appreciated.
 
I've already fixed 5 oil leaks since I bought the car.
The joys of driving a 21 year old car...

I already replaced crankshaft seal
Front or rear main seal? I'm guessing you've replaced the rear (the one nearest to the transmission). If you've never replaced the front, there's a possibility it's the culprit. It could also be crankshaft position sensor, or more likely, the oil pressure sending unit. Have you ever rebuilt the engine? The bedplate is notorious for leaking if you don't use the right anaerobic sealant or forget to install the O-ring. I think your best bet is to continue tracking down the leak, rather than replacing parts, hoping one will fix the issue. Maybe you can degrease the engine, then drive it progressively further, checking every 1/4 mile or so until you spot the source.
 
Camshaft seals are a high priority leak area on the 4g63, did you use sealant on the valve cover gasket in the corners and around the rounded cam ends like your supposed to? it will leak if you didnt. You can de-grease it and buy a bottle of uv oil dye at Autozone, add it to the oil, drive it, bring it in to a dark garage, shut it off and shine a black light on it to see the oil leak glow neon green/neon yellow to tell you where its coming from.
 
agree with cam shaft seals, guaranteed leak if not replaced at some point in the cars life.

Same goes for every seal under the timing cover......all of them, oil pump shaft, balance shaft, cam shaft, crank. Change every one of them with new OEM if your ever in there as they will leak for sure at some point if original. Any of these leaking should be pretty easy to figure out though, just clean things up like you have been and watch for oil to collect and drip from the bottom of the lower timing cover.
 
Ad some oil dye (just a little) to the oil. Run for 5 mins and take a black (ultra-violet) light around the motor and look for green/yellow oil. The dye can be very helpful but you can't let it spread all over the place or you wont find its origin.
 
@motomattx @EVLGSX op's car is a 420a, though most of your recommendations still apply.

I'll throw another hefty vote in with @1990TSIAWDTALON and say throw some dye in there, should make fairly quick work of tracking down the source(s) of the leak.

Couple questions for @BLACK'98DSM :
What's your pcv setup like? Do you have any pics of the general area you're seeing oil accumulate/leak from?
Being that you can seem to get it to leak during idling, crank case pressure seems to be a likely contibuter. Rpm+oil volume could be allowing oil to find a path not possible during idle/high vacuum, but there are few places i can think that would be affected, bed-plate seam being the main one.

I'd recommend checking your pcv valve and fresh air line, as well as making sure the ports themselves aren't gunked up with carbon/oil residue.
 
any pics of the general area you're seeing oil accumulate/leak from?
The oil drips from the oil filter, so I assume it is leaking on the passenger side of the engine. The whole timing system appears dry, so it should be coming from the rear of the engine (part closest to firewall).
 
Everything I have replaced was a cause of the leak, it wasn't at random.
Yes, I wasn't accusing you of doing that, just advising against it.

Yes, and only quality parts were used. Mostly performance ones.
The oil drips from the oil filter, so I assume it is leaking on the passenger side of the engine. The whole timing system appears dry, so it should be coming from the rear of the engine (part closest to firewall).
Is there a possibility that O-ring I mentioned was omitted, or that anaerobic sealant wsan't applied correctly to the bedplate? The area you're describing is exactly where the O-ring is. The crank angle sensor is also around there, which could leak if its O-ring failed.
 
ON 97-99 The crank position sensor is under the timing cover and does not hold back oil.

Image copied from another thread:

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ON 97-99 The crank position sensor is under the timing cover and does not hold back oil.
Nope, that's not where it is on the 420A--please keep in mind the sub-forum you're in. @BLACK'98DSM, it's right above the oil filter.

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@EVLGSX 420a man, not 4g63...haha

The cranks sensor is a possibility, it's definitely a good one to check and at least replace the o-ring or the whole sensor itself.

I have a worry: IIRC, it's possible for the head bolt on that corner of the block to not have the threads in the block cut deep enough, and it doesn't compress the gasket correctly. Did you use old, new head bolts, or ARP head studs?
 
I have a worry: IIRC, it's possible for the head bolt on that corner of the block to not have the threads in the block cut deep enough, and it doesn't compress the gasket correctly. Did you use old, new head bolts, or ARP head studs?
Good thought, but I think that problem was on the driver's side of the block.
 
Good thought, but I think that problem was on the driver's side of the block.

You are correct!
If the OP could get us some pictures, that would probably help the most
 
@EVLGSX 420a man, not 4g63...haha

The cranks sensor is a possibility, it's definitely a good one to check and at least replace the o-ring or the whole sensor itself.

I have a worry: IIRC, it's possible for the head bolt on that corner of the block to not have the threads in the block cut deep enough, and it doesn't compress the gasket correctly. Did you use old, new head bolts, or ARP head studs?




and I missed this too wow
 
I've already fixed 5 oil leaks since I bought the car. Last week there was another spot in the driveway... I already replaced crankshaft seal, valve cover seal, camshaft position seal, oil filter, and a couple others I can't think of off the top of my head. I've tried degreasing and idling for minutes to hours to see where the oil comes from, but it only seems to leak out when I drive it and have pressure on the engine. By the time I get home to check it, there is oil everywhere making it impossible to see where it came from. It is a very small and minor leak, but its nasty and annoying. My only 2 thoughts is that it could be the oil pump or the main seal, both of which are hard to replace. I'm tired of diagnosing this engine so your thoughts are greatly appreciated.
Are you watching the cam seals to make sure they aren't leaking on you? Are you seeing signs of oil on the timing belt? Do you have an external oil cooler? I've had one not seat properly and started leaking on me which sucks since there doesnt seem to be an easy way to change it without pulling the timing belt off. If you're getting that much oil accumulating before you get back home maybe clean everything as good as possible and then put the car up on some stands...let it run and see if you can spot the source.
 
Are you watching the cam seals to make sure they aren't leaking on you? Are you seeing signs of oil on the timing belt? Do you have an external oil cooler? I've had one not seat properly and started leaking on me which sucks since there doesnt seem to be an easy way to change it without pulling the timing belt off. If you're getting that much oil accumulating before you get back home maybe clean everything as good as possible and then put the car up on some stands...let it run and see if you can spot the source.
Dang.....maybe I should have read everyone elses replies before I chimed in...sorry hahaha
 
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