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Burning Oil Smell

1 February 2018
Richmond, VA
Hey all,

This is going to be a little lengthy, but that is to provide details.

Short Summary: Car smells of burning oil, even after turning off with less than 2 miles driving.
Request: Things to check? Common occurrence? Odd-ball things to look for?

Ok, so now on to the crazy-detail stuff.

About mid-2019, I noticed low oil pressure on my 1991 5MT vehicle. This was a known issue (by the gauge in the instrument panel) on these cars.

I had the car hooked up to an oil pressure gauge on the side of the block and it was confirmed to be low oil pressure.

The engine was taken apart and rebuilt over the course of 2+ years (long story, won't get into those details). Confirmed something small had gone through a rod bearing.

Because of some disagreement between me and the person who rebuilt it, I had to have the car inspected at an Acura dealership after the rebuild.

The Acura dealer confirmed oil pressure was good with a mechanical gauge on the side of the block. But also said that the VTEC solenoids were leaking.

So I had them replace the gaskets/seals on the solenoids.

After that repair, I drove the car about 50 miles to where it would be stored until I could get it shipped home. I smelled the oil then, but figured it is probably from the gauge check and/or the remnants of the leaking solenoids.

So since then, the car got shipped home and I've been driving it short distances about once per week. Probably have 200 miles on it since the dealer had it.

But still, that burning oil smell penetrates the car.

1) Could this still be remnants from the solenoid rebuild?
2) Is there something that could have been easily missed by supposed NSX-certified technician?
3) Is there an easy way to find something like this? I was thinking maybe the fluorescent fluid and black light method, but I'm unsure if it would stay around long enough to see with the heat burning it up.
4) Any suggestions for how, what, where to check for what seems like oil on the headers? Maybe a borescope or one of those auction website fiber-optic cameras?
5) Anyone had to fight this fight? If yes, what did you find was the cause?
6) Are there any common oil-leak sites (outside of the solenoids)?
7) If the solenoids are still leaking, any advice for how to bring this up to a dealer that is 900 miles away? Would a local dealer warranty another dealership's work?

Thanks for reading this far. I'm hopeful that someone here can help.

If you need more info that I haven't provided, please ask.
Could be remnants of the previous work; but, 200 miles does seem to be a bit long for it not to burn off of hot surfaces. Have you checked for fresh oil spots on the garage floor which might give you some indication of where the leak is located.

Possible oil leak sources;

- As I recall, the cam end plugs have a bit of a reputation for leaking oil. Problems during assembly or reassembly with old plugs that have deteriorated can result in leaking.
- It is not too hard to mess up the valve cover gasket if you are in a hurry
- Since the engine was taken apart I will assume the pan was off. Poor reassembly (overtightening the pan bolts) can cause the pan to leak.
- The oil filter pedestal can leak.
- Probably a lot of other places (including the solenoids)

I read into your comments that the engine probably has something over 200 miles since the rebuild. I am assuming that the outside would be decently clean which should make spotting fresh oil leaks easier. If the engine is not clean then external cleaning will facilitate spotting a fresh oil leak. Be careful with cleaning. You don't want to precipitate an ignition coil failure or some other problem by going crazy with a pressure washer.

Visually inspecting a C30 / C32 from the top is just a pain because it is so tightly packed into the engine compartment. A 1.5" - 2" telescoping inspection mirror is an option; but, you will also need a sharp focused LED flashlight because its dark down there! The alternative is an endoscopic camera. I have a Depstech DS 300 that I picked up on Amazon on sale for about $75 Cdn. 16' probe with dual cameras (front and side) and very bright illumination. There are probably others out there that are just as good and just as cheap. You will really need to have the car up on a hoist or jack stands in order to do a thorough inspection.

I would start with a visible light external inspection of the engine just because it does not cost $. On a clean engine you may luck out and find the wet spot. If that does not work then I would go for the UV dye in the oil. You are probably correct that the dye won't survive contact with a really hot surface like an exhaust system part; but, that is not where you will be looking. You will be looking at seams and mating surfaces on the block, anything where something is bolted together, to see where the oil is escaping. The oil (and the dye) will persist on the surface at the leak site even with the engine at operating temperature - been there, done that, got the Tee shirt (not on the NSX). Depending on the magnitude of the leak the engine may need a number of hours of operation to accumulate enough dye at the leak site to make it visible.

As a first step, I suggest a simple inspection from the top side. If nothing is obvious, despite my previous comment about 200 miles being a lot for the smell to persist, I suggest driving the car for a while to see if the problem persists. To be safe, monitor oil levels; but, based upon your description this leak does not seem like the type of leak that is going to show up on the dip stick. If after a couple hundred more miles the smell persists, then its up on the hoist / jack stands with a mirror or inspection camera and perhaps a dose of dye.

Good luck. Best case it resolves itself without intervention.
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Thanks for the input Old Guy. That is super helpful.
I'll do some shopping around and see what can be found for cheap and then start poking around, as you suggested.
Small update (for me to remember, but also hopefully for future searches).

Took car to another Acura dealer to have the work from the last dealer confirmed.
This new dealer found more (new) leaks, but said the solenoids were not leaking. This was confirmed with fluorescent oil dye. I will be unable to drive the car in the near future because of a personal trip out of town, but when I get back, I'll put some miles on it and see how it goes.

It smelled less like burning oil than I remember, so hopefully this time it is just the remnants, like I was hoping it was last time.

Where were the other leaks?
- Front valve cover gasket
- Front Plug Well seals

I'll have to get in there with the mirrors and borescope when I get back from my trip. But hopefully this is repaired. At least it is under warranty if it goes wrong again.
The leaking valve cover gasket isn't a surprise. It is not technically hard; but, does take some attention to make sure that the gasket is properly fitted in the cover. I like to use a little Hylomar blue as insurance in areas like that. Helps to keep the gasket in place when assembling.

Front plug well seals - do you mean the seals on the spark plug wells? I can see that they could leak; but, I am having some trouble figuring out how the oil could get up out of the spark plug well and on to the outside of the engine.

I would have assumed that when the engine was rebuilt new gaskets were installed. However, once a valve cover gasket has been mis-installed and left in that position for a while its probably toast. Best to get a new set. Rockauto sells a Mahle valve cover gasket set for the NSX for a very nice price

More Information for MAHLE VS50400 (rockauto.com)

Includes front and back cover gaskets, the seals for the retention bolts (which can be leakers) and your spark plug seals.
Just a reference note- the valve cover gaskets can be re-used up to about 6 months. After that, the rubber takes a set and will no longer be "squishy" enough to seal properly. The most important thing, however, is clean, clean, clean. Both gasket and mating surface. # 1 cause of cover leaks on the NSX is poor surface prep. # 2 is a pinched or folded gasket. It's due to the very difficult access when the engine is in the car. Most techs don't bother to clean it very well because it's so hard to reach back there. They just kind of wipe it with a dirty rag and install the cover. Then a year later- bam you've got a seeping leak.
Small Update (and sorry for taking so long to respond to the awesome info)

1) The Acura dealership replaced the front valve cover gasket.
2) The Acura dealership also replaced the "Front Plugs". I assume they mean the caps on the ends of the cams, on the front bank, but it is an assumption.

Result: Significant reduction in burning oil smell. I'm hoping what I smell now (which is VERY faint, is just remnants).

So, on to the next issue, which was the surging Idle.
I will put that in my other thread related to this specific car to keep us on topic though.