Pesky oil leak, rear bank

S

shern

Contributing Member
Joined
29 February 2012
Messages
195
Location
Chandler, AZ
I've been fighting an oil leak on the rear bank for quite some time now. The car is a 98 NA2. The oil is leaking and dropping onto the exhaust manifold causing burned oil smoke.

I've replaced both of the usual suspects including the spool valve gaskets as well as the rear valve cover gaskets to no avail (full gasket set). The leak does not appear to be coming from the rear cam seal.

With the car on the lift yesterday, I did notice some oil at the lower side of the head right above the exhaust manifold heat shield on the driver's side (trans side). Because the manifold sweeps up, it's really tough to see the lower section of the valve cover to source the leak. I've run my finger along the valve cover and can't find oil.

Therefore, the leak is either coming from the valve cover gasket (potentially install issue?) or some other source. What other sources exist in this area?

Any help is appreciated.

Steve
 
Clean the entire area completely, then look for the highest wet spot. Did you use Hondabond when you installed the new VC gasket, as specified?

Regards,
LarryB
 
Larry Bastanza said:
Clean the entire area completely, then look for the highest wet spot. Did you use Hondabond when you installed the new VC gasket, as specified?
Click to expand...

Because of the impeding exhaust manifold and associated heat shields, the whole area is covered up and impossible to clean. I could start by removing the shields and give it a shot.

I didn't follow the full process for VC installation including hondabond. I will pull again and follow exactly.

But it doesn't sound like there is another source for oil in the area? It must be the VC?

Thanks
 
Get a can of BrakeKleen and srray the heck out of the area to get it clean;).
 
the best way I have found to fix a pesky rear bank oil/valve cover leak is to remove the old gasket and with some hondabond glue-down the new one in a few spots, particularly around the corners. don't let the hondabond dry overnight to a hardened state but for a couple of hours to set it. its easiest to install the rear bank valve cover if you have the plastic upper air dam removed,(right behind the glass). it has proved me well for many nsx's I have worked on.
 
Hondabond arrived yesterday. I'll dig into it this weekend and let you know.

Thanks for the suggestion on removing the upper air dam/deflector. Hadn't even thought about that.
 
Briank said:
You do have new rubber backed hold down washers? They do flatten out with time and don't properly hold the cover down.
Click to expand...

Yes

Full valve cover kit used inclusive of VC gasket, hold down washers and spark plug tubes. Also replaced the TB cover gasket.
 
Update (and associated question)

Recently had the TB/WP done inclusive of VC gasket replacement (by the dealer this time). Received the vehicle back and the oil leak is still there and burning on the exhaust manifolds. The car went back in and is still burning oil, mostly on the rear bank.

The dealer tells me that there are a number of "head seals or plugs" that are located on the head in the vicinity of the exhaust manifold that need to be replaced. There is a number of these head seals in both the front/rear banks that require manifold removal and replacement.

Is this common? I can't find any info on exploded diagrams of the NSX head.

Steve
 
No No, not cam plugs at the end of the head (4 in total, 2 on each head). That was the first question I asked when I received the ~$900 quote.

These are "plugs or seals" located in the vicinity of the exhaust manifolds. That's the communication I received. I'm scratching my head here.

- - - Updated - - -

Received a pic from dealer. These look to be threaded plugs along the lower side of the head, close to the manifolds.
 
Something I've always done on valve covers, including the NSX, is when tightening the cover down loosely (using just a socket in my hand, and way before final torque), tighten the lowest bolts first, then the upper ones. Then torque to spec and per specified order. That gives a slight bias to a better seal at the bottom.

However, that rear cover is a @#!*! to get into place without hitting the gasket on one of the studs. I agree with all on the use of Hondabond and with arny213213 on removing the plastic trim to get all the wiggle room possible.
 
I have never heard of those plugs leaking, since they are down hill from the leaking head cover its going to look like they are leaking. Take is back and tell them to find and fix the problem with the head cover gaskets, they are the obvious problem.
 
Last edited:
Yes it is. Easier to see and capture problem statement. I couldn't for the life of me see anything on rear bank due to routing of the manifold. Tech mentioned with mirrors he was able to see it on rear bank.

I'm quite skeptical myself. We'll see.
 
UPDATE

The tech was correct on the diagnosis. The manifolds were dropped and these "sealing screws" were replaced. Both front and rear heads were completed as they both showed leakage. I've had the car for approximately 2 weeks now and not a hint of oil burning or smoke.

The part numbers are:
- 12208-PG6-300 Screw, Sealing x4 (#3 below)
- 12206-PH7-300 Bolt, Sealing x2
- 90004-PE2-005 Bolt, Sealing x2 (#11 below)


nsxhead.gif
 
wow! this is something new!! .... great job on the tech's part to think outside the box of usual suspects.

please keep us posted if the leak returns.
 
Bummed this pic off a fellow primer that clearly shows the sealing plugs that were leaking and replaced.

qa3ygaqy.jpg
 

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