Oil Leak - Timing Belt Cover

[exSeSSive]

Since this is the DIY forum, I figured several members in here would have great input.

So I bought a 97 with 70K miles. The timing belt was changed at 50K miles. (I'm not sure how long ago that was - I need to dig through the records.) But I got under there last weekend to check the state of things...And found 2 oil leaks.

Neither is fast moving - they're both dirty/grimy oil spots. One is the head cover gasket/cam plug on the rear bank/driver side. The other is coming out the bottom of the timing belt cover.

The TB cover leak is the one I'm concerned about. I've seen this several times on other Honda products, but this is my first NSX ownership. Another NSX owner has told me that it sounds *very* unusual to see a leak in this place.

> Is this a common leak point?
> As with other Honda products, it is *very likely* there is oil getting on the timing belt?
> Any other thoughts?

(Disclaimer: The car was religiously dropped off at an Acura dealer for 2500 mile oil changes by previous owner - so I didn't expect this. I am upset at myself for being a little too eager and not catching this, but for the deal that was struck, I had to move fast. And I am still *very* happy with my purchase. :biggrin: )

 

[MJK]

Common leaks are:

Cam plugs (usually more a seep than a leak)
Oil pan gasket
Valve covers
Vtec spool valves (hi pressure oil)

I don't know what would get oil on the timing belt cover, that sounds strange to me. I would PM Larry Bastanza for an educated opinion, he is a guru of all things NSX.

I am upset at myself for being a little too eager and not catching this, but for the deal that was struck, I had to move fast. And I am still *very* happy with my purchase.

Yes, it is good that you moved that fast otherwise it would be my problem. Let me know if you want to unload that heap when I see you at Sebring! :tongue:

 

[Larry Bastanza]

One is the head cover gasket/cam plug on the rear bank/driver side.

This is most likely the actual valve cover gasket. Cam plugs do not leak all that much. It could be a VTEC Spool valve seal, but this is usually a lower leak then the valve cover.

The other is coming out the bottom of the timing belt cover.

Check to make sure that this is an actual oil leak. A common issue is that the cam position sensor assy, has "potting" sealer and over time this material will tend to melt and send a small stream of it's tar like substance running dowm the inside of the timing belt housing. If it is not oil, that is what it is. This can also be the valve cover gasket. The only other thing is a bad cam seal, although this is not very common.

HTH,
LarryB

 

[sjones]

This is most likely the actual valve cover gasket. Cam plugs do not leak all that much. It could be a VTEC Spool valve seal, but this is usually a lower leak then the valve cover.



Check to make sure that this is an actual oil leak. A common issue is that the cam position sensor assy, has "potting" sealer and over time this material will tend to melt and send a small stream of it's tar like substance running dowm the inside of the timing belt housing. If it is not oil, that is what it is. This can also be the valve cover gasket. The only other thing is a bad cam seal, although this is not very common.

HTH,
LarryB

this is a little off topic but Larry should the cam position sensor assy, be replaced when doing a timing belt? Mine use to have those tar drip spots but stopped a few months ago. The tech told me it was one of the sensor housings and to not worry about it unless i ever had a check engine light which i never have.

 

[nsx2tall]

An oil pan gasket leak can be wicked up into the timing belt cover and give the appearance of a cam seal leak. I say this from experience in that I had a non-NSX specialist change the oil pan gasket and then a year later tell me I had a cam seal leak. I took it to AoB and surprise, the oil pan gasket had a leak-- again. Cam seals were surprisingly non-leaky.

Though, John at AoB said cam seal leaks are not uncommon, too. He has a way of doing oil pan gaskets that might be worth copying.

 

[Larry Bastanza]

this is a little off topic but Larry should the cam position sensor assy, be replaced when doing a timing belt? Mine use to have those tar drip spots but stopped a few months ago. The tech told me it was one of the sensor housings and to not worry about it unless i ever had a check engine light which i never have.

I would not be too concerned about this. Your may have stopped leaking because much if the "tar" has run out already. I have never changed this sensor as part fo a routine timing belt service.


HTH,
LarryB

 

[exSeSSive]

Thanks for all of the info guys. I am familiar with the black "tar" substance, and while I do see that as well in places, this is definitely oil.

I got the car up on a lift and took a look at it.

On the rear bank, the head cover gasket is *definitely* leaking (although it's mostly dry now), and you can see where it's run down the entire back-side of the head.

The wettest spot is (trying to illustrate) - Looking from the driver's side at the rear bank (cylinders 4-6) and defining the END of the head/valve cover to be the side closest to cylinder # 6. The corner on the right (closest to rear of the car), is the worst. If given enough time, I'll get a few drops cooking off on the exhaust heat shield.

The oil pan gasket leak *looking like* a timing belt (TB) leak is an interesting thing. But it's not just that the bottom of the TB cover "has oil on it" - it's actually "collected" at the base of the TB cover. Which makes me think it's coming from above or from inside.

What I *am* trying to do is avoid the cost (someone else doing it), or the hassle (me doing it), of getting into the TB, since TB/WP was replaced about 20K miles ago. But at the same time, the possibility that oil is getting ON the TB worries me quite a bit. Am I worrying too much about that?

With some of the info posted here, I am thinking a good route would be to:

- Replace head cover gasket.
- Replace VTEC/spool filter/gasket (preventative - might as well.)
- Leave the cam plugs alone - maybe not leaking? And I don't want to mess with the valvetrain to replace them. (I've heard there are some shortcut ways to change the cam plug that doesn't follow the service manual?)
- Replace the oil pan gasket (fairly easy to do - I can't tell for sure if oil pan is leaking or coming from above.)
- Clean it all up - including TB cover.
- See if any leaks show up.

One other FYI: The TB cover really has 2 "oil spots": one is at the very base of the cover (bottom of the "V"), the other is along the crack where the bottom TB cover piece comes together with the upper-right TB cover piece. Looking from the passenger side, this would be the right bank (cylinder 1) TB piece. Does this change the likelihood there is a leak behind the TB cover instead of from above?

How does the plan sound? Anything seriously flawed?

Thanks again for any input! I've already picked up so much NSX knowledge from Prime, and I can tell it's going to save my a$$ in the future as well. Once I "get to know" the car a little better, I can hopefully add some value back in.

:biggrin:

 

[Larry Bastanza]

First thing is that you have your cylinder banks reversed. 1,2,3 are the rearbank, 4,5,6 are the front bank.

Before changing anything, I would get under there with some brakekleen, clean everything off and see if you can get a better idea what is really happening.

My only concern is your comment about oil at the seam of the upper and lower cover, that is strange to me. I would consider removing one valve cover, and taking a peek in there.

HTH,
LarryB

 

[exSeSSive]

Man, I must be on crack - I was just looking at the 91 service manual last night. It was a *late* night if I screwed that up...

Yeah, I'm backwards. (I like to think of it more as a 'talent.')

Homer Simpson "Doh!"

 

[ktan]

have you considered Cam Seals behind the timing belt gears. I'm pretty sure thats where mine is coming from due to my carelessness reinstalling the cam seal when putting the motor back together, if it is slightly angled, it will leak ... I've just left it for now, but will be fixing it shortly.

Kevin

 

[nigel]

To add to what Larry said, Do what he said with cleaner. When you are sure it is completely dry, a dry towel won't hurt, get some spray foot powder, ('cause it's cheep) and spray all the suspect areas. Be sure there is a good white coat. Not to thick. Run the engine and look for the leaks. They will jump out at you! An old HRC trick I still use to this day in aviation. When you confirm the areas, rinse off with water or just wipe.

Cheers
nigel