Valve cover (rear) leaking oil

[goldNSX]

Last year I did a valve adjustment with new gaskets/Hondabond etc. Kit #4 in the pic. During the year it has been leaking from the lower edge (towards the header) the rear valve cover on the TB side. It's not leaking badly but got annoying. Within a year the inner boot of the right axle is covered with engine oil, so I took it off, analysed it with confusing results.

The TB gasket (#7 in the pic) in the cover is about 1/2'' too long, I also suspect that TB gasket takes pressure off the main cover gasket of #4 -> oil leak.

The TB gaskets are two different part no (#6+7). Is it possible to mix them up? The other edge of the rear (same) cover just fits fine.

Solutions?
Hondabond in that area too?
Cut 1 mm off the TB gasket?

 

[Old Guy]

I can't comment on the part number mix-up.

I would advise against the copious application of Hondabond (if that was what you were thinking about).

In the absence of somebody confirming that you obviously have the wrong part, if you are thinking about shortening the timing belt cover gasket (which really does look to be about 10 mm too long), I have had good results fabricating O-rings by cutting the O-ring cord diagonally and then bonding the rubber back together using Loctite 406. 406 is not cheap; but, not ridiculous in price. I have heard that Loctite 404 is also a very good product for elastomers; but, its price does tend to approach the ridiculous region.

 

[goldNSX]

Thanks for your opinion. If I cut the gasket the next question is where? That's why I did another measure. The distance between the gasket being fitted/not fitted is 5 mm regarding where the higher part of it sits finally. I'll have to compare to the counterpart, means the TB cover itself. You can't see it in the picture but the gasket seems to have had more pressure for exactly the same 5mm right in that area. I'm curious what to find (tomorrow)...

 

[Mac Attack]

The TB gaskets are two different part no (#6+7). Is it possible to mix them up? The other edge of the rear (same) cover just fits fine.

You could not install these in the wrong places due to the way the OEM engineers made the positioning tabs and the physical size differences between them. See this for-sale thread for a nice comparison underneath the covers:
http://www.nsxprime.com/forum/showthread.php/206339-NSX-NA1-Red-Valve-Cover-pair-400?

But, that gasket #7 does not look right either. Counterfeit part? Can you buy a new one separately? That's what I would do (as long as this one fit better). I've run into OEM Honda supplier quality problems in the past (bad rod bearings for example).

I don't think you want to shorten the thick part of the rubber in your picture. If anything, you want to cut and shorten the thin part of the rubber. Look at the top of your rear plastic TB cover. The thick part of the rubber gasket should begin where the plastic TB cover drops down. At least that is how mine is. I've modified your picture to show where the thick part of the rubber should begin, but measure yours to confirm.

View attachment 158610

Also, cutting that gasket and getting a good seal later is not that important here. I'm looking at buying cheap mag covers so I can cut them and expose the cam gears to make timing changes easier. Sure, it's to keep debris away from the gears and belt, but the opening between the crankshaft and the lower plastic cover would allow more contaminates to enter the TB area than if you just cut it, put some Hondabond between the cuts, and reinstall it.

Sorry. Working on the rear valve cover is a pain - especially as you get older. I did mine with the engine out of the car, and I'm thinking about dropping the engine subframe again the next time I need to do the TB.

Edit: Hopefully the engine oil did not get onto the TB. Was it clean?

 

[Kaz-kzukNA1]

Quite busy at the moment so just brief insight.

As [MENTION=12356]Mac Attack[/MENTION] mentioned, would be surprise if you managed to install it in wrong places.

Some photos with TB rear cover.

Can't deny other possible causes but example of one of the most common rear bank oil seepage mode.
Seen it on so many NSX engines….


By the way, I saw exactly the same status as your swollen/swelled gasket on several engines.
They were all at the rear valve covers.
Didn't pay much attention at that time because they were not installed properly any way (cut/trapped at other places) but interesting to see on yours as it did look like installed properly.
Effect of engine oil chemical???


Just a matter of interest, did you replace the metal/rubber washers #22 in your parts diagram at the same time?

Also, won't directly cause the seepage but attribute for the valve cover alignment difficulty during the installation.
If your NSX is 91 model, are you using the original or later spec TB Mid covers (Front & Rear) ?



The rubber gasket #6 & #7 are more of dust/splash proof and not for oil seal purpose.
In fact, even without them, if the main gasket #4 was installed properly with oil free mating surface at the cyl head, the oil seepage won't happen for several years.

With the engine inside the bay and both Eng/Gbox side mounts still connected, the engine won't drop any further so very limited working space available around the rear bank.
If you have FI setup or any aftermarket parts inside the eng bay, that will even reduce the available space further.

One of the most difficult section to create oil free surface while keeping the eng inside the bay marked in yellow.

Looks easy at first but once assembled then…..
Imagine you need to access that narrow channel between #1 cam holder and cover plate while keeping engine inside the bay.....

Any seepage behind the TB cover plate marked in yellow (1st photo above) would drip down from the small opening marked in blue (2nd photo above) at the cyl head then lands around the oil cooler pipe/hose and then inboard joint boot of R-driveshaft.
Over the years, the small gasket at the back of the cover plate will take set and no longer creates good seal against thermal expansion/contraction and seep behind the gasket.
The oil seeped from the blue marked area (1st photo above) will run down along the cyl head and depending on the air flow, it will drip down to several different places.


If the #1 cam holder was lifted in the past or never serviced before, the liquid gasket applied next to the brown cam seal may no longer making good seal.
However, the amount of seepage would be much lower than the one from around the yellow marked section.

Hope you can fix the seepage.


Kaz

 

[goldNSX]

Thanks very much for you extended post, Dave.

I finally had a chance to take pictures of the TB covers. One is the upper edge, one the lower edge (the bloddy one) of the rear cyl head. Luckily, there's no oil on the TB.

What did I find? Well, disappointingly nothing wrong. I've took some measurements of the area (from the pictures) and the rubber shape corresponds to the TB cover's shape by +-1 mm. So there's nothing wrong with the (still original) TB cover gaskets on my 91.

I guess I'll have to put it on 'dry' (without Hondabond) and check again. But I don't think I did anything wrong the last time.

I still think about cutting 1/2 mm off the gasket and use Hondabond instead to give it a seal again water/dust and mainly to transfer more pressure to the main cyl head cover gasket to avoid oil leakage.

upper edge of the rear cyl head


lower edge of the rear cyl head
The oil went from the valve cover gasket along the TB cover gasket to a wire and then down on the inner axle boot.

 

[goldNSX]

Thanks for your extended post, Kaz

To answer your questions:

Just a matter of interest, did you replace the metal/rubber washers #22 in your parts diagram at the same time?

I've just replaced the two between the ign coils per head (totally 4, not 12). I know they do flatten but one question: when you torque the nut of does the metal part OR the rubber part of the washer determine the reached torque? Or with other words (not easy to explain): does the metal part of the washer contacts the seat of the long shaft in the head and the pressure on the gasket is a result of the thickness of the upper and lower rubber parts? I guess YES because you can't stop the leakage by just torqueing the hell out of it, right?

Also, won't directly cause the seepage but attribute for the valve cover alignment difficulty during the installation.
If your NSX is 91 model, are you using the original or later spec TB Mid covers (Front & Rear) ?

A new TB mid cover came with the new water-pump. The ones above it (left and right) are still the ones that came with the car.

 

[Larry Bastanza]

JMO, but you should always replace all 12 washers, which are part of the seal kit, PN 12030-PR7-010, although this kit is shown applicable for later year cars it is applicable for all years. Also remember that the gaskets on the valve cover that seal with the timing belt cover tops is really for sealing dust out of the timing belt, not to seal for oil, like the overall gasket.

HTH,
LarryB

 

[Honcho]

JMO, but you should always replace all 12 washers, which are part of the seal kit, PN 12030-PR7-010, although this kit is shown applicable for later year cars it is applicable for all years. Also remember that the gaskets on the valve cover that seal with the timing belt cover tops is really for sealing dust out of the timing belt, not to seal for oil, like the overall gasket.

HTH,
LarryB

Agree 100%. The new rubber is "squishy" and the old rubber is stiff and flattened. If you put only some new washers, you will have uneven pressure and an uneven mating surface around the perimeter of the valve covers, which can cause a seeping leak over time.

 

[goldNSX]

By the way, I saw exactly the same status as your swollen/swelled gasket on several engines.
They were all at the rear valve covers.
Didn't pay much attention at that time because they were not installed properly any way (cut/trapped at other places) but interesting to see on yours as it did look like installed properly.
Effect of engine oil chemical???

Kaz

I guess that's on the right track. I've two more pictures for better comparison. While the gasket's shape still matches the shape of the TB cover (if squezzed in the cover) the swollen end of the gasket DOES lift the cover more than on the other side. The difference is about 2 mm between the two. I'm going to cut the swollen end a little bit down. And as I really want to know if this helped I'm going to mount the cover with the old washers (the new ones should arrive in a month if the Honda parts God is willing).





Thanks to all who replied!

 

[goldNSX]

Some more pictures. Hondabond will do the rest on the TB cover to keep the TB from dust and water. Going to order a new TB gasket as well...New washers are just half of the job if the TB gasket got swollen IMHO. I'd recommend to replace both or to cut the swollen end.

before


after