Found Oil Leak While Inspecting Timing Belt & Changing Clutch Slave

[99 rs]

I was changing out my clutch master and slave cylinders and after I got to the point in the first picture below, I looked up at the engine side and saw a dreaded oil leak. I tried to find where it was coming from but can’t seem to pinpoint it. It seems to be pooling up on some mini exhaust looking piping (it has an expansion joint in it) at the very front of the engine in front of the forward cylinder head. At first I was just going to snug it down a little more but figured I should run it by you guys first.

The actual question is can you identify where this oil leak is coming from? If you want more pictures I can run out and grab them.

The original work:

Now the actual leak, this next picture is looking down from the top of the engine, front cylinder head, on the corner closest to the interior and center of the car. The oil is pooling on the bottom of this flange.

The next few pictures I basically put my phone up as high as I could and just started blindly shooting as I couldn’t really get my arms in there and still push the picture button. The bottom of the picture above is shown next. It almost looked to me as if that lower threaded plug was the culprit but that wouldn’t make sense from where the oil bubble is. I was thinking of just cave man tightening those 2 down but will hold off for now.

In the back of the picture below you can see the expansion joint.

The oil is also pooling near that oil pressure sensor looking thing.

If you guys know of a place I can start to look for the leak please share.

 

[99 rs]

I didn’t want to post this in any of the timing belt threads as I don’t want to re-light the timing belt fire/witch hunt. I’m willing to become a statistic and you guys can properly pitch fork me if it comes down do it. I inspected the timing belt and it looks absolutely mint but I know the bearings in the rotating stuff could go on me at any time. I won’t list my mileage or year as I’m curious to what you guys guess as to what mine is at. I’m going to run this belt for this season and then do the full belt, water pump, and coolant hoses next spring. My primary focus is that oil leak above though!

Magnesium goodness

Do you guys know what the coating is on the cam lobes? Mine is wearing away but it could be since I cold start this car all the time.

 

[goldNSX]

Guess: 8 years and 50k miles. But it won't help.
Every engine shows some kind of sweating oil here and there. After some time people notice it but it looks worse than it is. As long as it's not excessiv...

 

[Chase_acura]

Looks like vtec seals and or oil pressure gauge seals. Both are common

Sent from my SM-G950U using Tapatalk

 

[MotorMouth93]

The cam lobes being shiny with the dark coating worn off is normal.

I won’t list my mileage or year as I’m curious to what you guys guess as to what mine is at.

No thanks I'm good.

 

[Bram]

I just had my T/B replaced last month after 20K and 10 years, all the marking on the belts are quite visible and complete, so based on that I'll say your belt is way beyond that milage.

As for the leak, dunno....could be the head cover gaskets.

Bram

 

[Honcho]

It's almost certainly a valve cover gasket leak- your 4th picture is the giveaway to me. A long time ago, LarryB taught me that when you see oil on the NSX engine, "look up." His point was that while things like the spool valves and cam caps can leak, it almost always is the valve covers. There's not a lot of torque on the nuts, so any defect (pinched or misaligned gasket) or dirty spot can result in a slow, seeping oil leak. I would replace the gaskets (they take a set after about 6 months) and make 100% sure that the mating surface on the head is flat (scrape off debris) and surgically clean. It's really easy to roll and/or pinch the rear gasket if you are installing with the engine still in the car(been there done that lol), so I would get it on there and then inspect all the way around with a flashlight to make sure the gasket is sitting flat. Then torque it down. Should solve it. Won't hurt either to replace the spool valve gaskets and oil pressure o-ring. Cheap parts.

 

[99 rs]

Thanks guys for the responses. I'm hoping it was the valve cover gasket too. I put it back on over the weekend and wiped everything down really good so I'll wait and see where the drips show up.

The belt is original to the car. It is 15 years old in 2020 (car is a 2005 model) and the current mileage is 19,861 miles. We have a very short season up here so it doesn't get driven too much.

 

[JackMikk]

Are there any changes?

 

[goldNSX]

I bump this one because it shows the two screws.

What the bloddy hell are these for?

Are they prone to leak? I'm hunting down an oil leak.

 

[Big McLargeHuge]

Those are plugs for the oil galley holes, hex heads. I had a decent leak from them, so during my clutch install I took them out and installed them again with PTFE tape or oil/heat resistant sealant and they've been dry since. [MENTION=33247]MotorMouth93[/MENTION] answered that for me in my build thread. Actually a decently common issue it seems.

The oil drips down the plugs and onto the front engine mount then drips down onto the bottom of the transmission cover where wind blows it along the bottom of the trans. I thought it was VTEC gaskets initially. The rear head has 2 more plugs but I couldn't even get to them with the transmission removed.

 

[goldNSX]

Thanks very much for your reply. Good to know that oil is behind them (and not coolant). My friend thought about coolant as their hex inside is somewhat greenish.
I first thought about a leaking edge of the valve cover gasket but it's pretty dry up there. In the rear, the oil is dripping onto the coolant line (color bronze) and finds it's way onto the front header end. I've the cats out right now and will give it a try in the next days.

What amount of oil to expect when removing them?
What torque? I couldn't find any specs in the SM nor a replacement part in the parts catalog.

 

[Big McLargeHuge]

Yep, just oil. My rear plugs were not leaking though I tried to re-thread them anyways, I just couldn't find a way to remove them without bending the coolant lines far away so I just left them be.

They'll dribble a bit of old oil that can be caught with a rag. I don't think they have any torque specs or a P/N I know of, "gutentight" with a normal length allen/hex key wrench should be fine. They'll be a bit tight with a lot of thread tape but you'll feel when it's tight enough/bottomed out.

 

[Old Guy]

I do recall that Kaz responded to a post on oil leaks and identified the plugs as the culprit. I can't remember whether he provided any guidance on fixing the leak and I can't find the post.

 

[goldNSX]

I do recall that Kaz responded to a post on oil leaks and identified the plugs as the culprit. I can't remember whether he provided any guidance on fixing the leak and I can't find the post.

Thanks for the hint. I've searched both forums but couldn't find anything.

On the rear, the lower one is a bit tricky to get to. Flexing a hex wrench will do the trick.

 

[MotorMouth93]

They are taper plugs, and taper threads often don't have a torque value specified for a variety of good reasons.

I'd find a "turns from finger tight" table for the thread pitch in question and use that as a starting point.

 

[goldNSX]

The bad news is that the rear 97+ header has to be dismounted.
The other bad news is that I've found 18115 gaskets but with the ending -A02 while in the parts catalog it says -J02. Back in 2012 I guess I was using -A02 with a modification, not sure.
The other quite embarassing question is where the washer goes to - screw or nut?

 

[Kaz-kzukNA1]

Regarding the metal gasket, strictly speaking, should be replaced but can be re-used.

The gasket ending with -A0x (-A01 superseded to -A02) is for the 3.0L C30A spec.
The -J0x (-J01 superseded to -J02) was introduced since 97 for 3.2L C32B spec but can be used on the 3.0L as well.

The opening of the -J02 gasket is slightly larger than the -A02 one and due to the deviation in the geometry of the cyl head exh port opening, I normally recommend using the -J0x for any engine.
It's a tiny difference so may be on this occasion, just re-use your existing -A0x one and replace it to -J02 next time when you carry out majour engine service???


Not sure whether we are on the same subject or not and possibly I missed something as I'm slow to catch up these days with the Forum here and back in UK....
Are these for the CAT, etc???

The nut looked to be the OEM self-locking flanged one.
The flange should make direct contact against the mating surface without the washer unless there is another reason not to do so.

Not sure about the washer.

The bolt looked to be the aftermarket stainless one.

Not sure where you are using these but if at the CAT, the OEM is spring loaded swivel doughnut gasket setup so I can see the nut in use but not these washer and the bolt.
Or, are you using NA2 OEM header with the NA1 3 stud bolts CAT???


As a side note, please avoid using same stainless material for the bolt and the nut under high temperature vibration environment.
100% guaranteed to bond and seize together and you don't want ending up cutting stainless material under limited space....


Kaz

 

[goldNSX]

Thanks very much for the info, Kaz.

I'm using 97+ headers on a 91 engine, mounted in 2011. There was a problem back then but I don't know exactly how I solved it. There were three pins in a gasket and they interfered with the header. I had to remove the pins which held the gasket together and make sure the 3 layer gasket was positioned correctly. All worked fine back then an no leaks until now. I've had a look in my parts ordering spreadsheet and didn't find any -J0x gaskets, just some -A02. Not sure if I reused the old modified ones...going to use new ones for sure. I have time but ordering only gaskets is too expensive.
Well, I hope I don't have to remove it during the next 10 years.



The screw/washer/nut came with the SARD cats. I'm running adapters and still the 91-94 cats. I guess they're ok to be mounted.

 

[goldNSX]

Corpus delicti and pretty rare picture I believe.



There's nothing up there, no conical seal. You can see a conical part on the screw but no counterpart in the hole. It's held by a thread locking sealant > Loctite red and it's a PITA to remove. 10 deg. -, 10 deg. +, 10 deg. - ... seized? No. Use heat? Better not. It needs 50 Nm to remove, after it's broken free, it's ok. Threads cleaned, no problem screwing it in.

As for the rear has to come out everything of the exhaust system, I'm not sure if PTFE is holding long enough. I'm searching for the longest living solution. I wish Honda did not design these bolts. What for?



I won't have a chance to do it on the smaller one. But I think the bigger one has a much greater (6-8x) higher area to let it leak.

 

[Honcho]

Corpus delicti and pretty rare picture I believe.

There's nothing up there, no conical seal. You can see a conical part on the screw but no counterpart in the hole. It's held by a thread locking sealant > Loctite red and it's a PITA to remove. 10 deg. -, 10 deg. +, 10 deg. - ... seized? No. Use heat? Better not. It needs 50 Nm to remove, after it's broken free, it's ok. Threads cleaned, no problem screwing it in.

As for the rear has to come out everything of the exhaust system, I'm not sure if PTFE is holding long enough. I'm searching for the longest living solution. I wish Honda did not design these bolts. What for?

I won't have a chance to do it on the smaller one. But I think the bigger one has a much greater (6-8x) higher area to let it leak.

BTW the threads are 16x1.25.

Very helpful pictures, Gold. The machine shop is going to remove these for cleaning on my heads. What sealing solution did you settle on? I wonder if Hondabond HT might work better than PTFE tape? I wish we knew what material Honda uses at the factory. Maybe [MENTION=25737]Kaz-kzukNA1[/MENTION] can help here, since I imagine the Honda Refresh Center must perform this task on their engine overhaul service. I believe these plugs are used to seal the oil galleys that are cut as part of the machining process when the heads are made.

 

[goldNSX]

Very helpful pictures, Gold. The machine shop is going to remove these for cleaning on my heads. What sealing solution did you settle on? I wonder if Hondabond HT might work better than PTFE tape? I wish we knew what material Honda uses at the factory. Maybe [MENTION=25737]Kaz-kzukNA1[/MENTION] can help here, since I imagine the Honda Refresh Center must perform this task on their engine overhaul service. I believe these plugs are used to seal the oil galleys that are cut as part of the machining process when the heads are made.

I thought about Hondabond HT and PTFE (Teflon) tape but regarding the work to get there I'm having a look at the Loctite product line right now.
For sure it must be sealing, resistant to oil, heat AND vibration. It must be a combo of sealant and theadlocking.

 

[goldNSX]

A01 gasket on 97+ header.

1. Flexing it off.
2. Install like this.
3. Drill holes in the header (no).
(3. ordering a 97+ gasket is not an option)

 

[Honcho]

A01 gasket on 97+ header.

1. Flexing it off.
2. Install like this.
3. Drill holes in the header (no).
(3. ordering a 97+ gasket is not an option)

View attachment 168837

I'd just remove it (drill or pop out)- it's nowhere near the exhaust port.

 

[MotorMouth93]

Corpus delicti and pretty rare picture I believe.

View attachment 168828

There's nothing up there, no conical seal. You can see a conical part on the screw but no counterpart in the hole. It's held by a thread locking sealant > Loctite red and it's a PITA to remove. 10 deg. -, 10 deg. +, 10 deg. - ... seized? No. Use heat? Better not. It needs 50 Nm to remove, after it's broken free, it's ok. Threads cleaned, no problem screwing it in.

What do you mean? It's just a taper thread plug, there is no conical seal involved. I'm fairly certain it is a 3/8" BSPT plug so no need to over complicate things, you can either use teflon pipe tape, Hondabond, or Permatex makes a thread sealant that would work as well.

As for the rear has to come out everything of the exhaust system, I'm not sure if PTFE is holding long enough. I'm searching for the longest living solution. I wish Honda did not design these bolts. What for?

Honcho is correct, these holes were necessary to drill the oil galleys in the heads during manufacturing.