Replacing the round seals at the end of the Camshaft

[I Grok NSX]

Hi All-

I have an oil leak at the rear end of the Front Valve cover. Can't say for sure where it's coming from but I'm replacing the valve cover gaskets. I also purchased the two round rubber plugs that are located at the end of the head - they cover the end of the cam shafts.

How do I replace those round plugs? It looks as if I need to loosen the valve train, but I don't really want to do that. Is it possible to remove the plugs by just pulling, forcing the plugs out and replacing with the new plugs?

I did a search and didn't find any thing to that question. Also, the service manual shows the plugs but doesn't mention how to replace them.

Thanks in advance.

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1994 Green-black roof/tan, 5 speed
Do you know of another Green-Black roof NSX?? Please email me if you do.

 

[4AU4LIFE]

That is a good question. I would also like to know the answer.

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92 RED/BLACK 5-SPEED

 

[Periokid]

I think LarryB knows that answer.

Larry, you listening?

 

[Larry Bastanza]

Litesokneecough,

These are called the "cam plugs" and it is common that they leak after a while. You will have to loosen the cam covers to change them. These are the aluminum cradles that sit above each cam shaft with many bolts. See the manual. You will not have to remove them, in fact DO NOT. Loosen them up enough to raise them and pop the plug out. Put HondaBond around the new plugs, insert them, then properly torque the cam cover in sequence, exactly as the manual describes.

Do one at a time. I would also recommend when you are doing this take a large paper clip (the black ones for large documents) and clip the timing belt on the respective cam so there is "0" chance the belt will slip.

Be cautious not to remove the covers so the cam does not come out.

Let me know if you have any questions.

HTH,
LarryB

 

[DanO]

As usual, Larry offers awesome advice! Please look at page 6-38 of the service manual to get a feel for how many bolts Larry is talking about! Larry suggests doing one at a time (I assume he means one plug not head) but it may be difficult to do just one rail and stay within the torque sequence listed in the manual. The front head has four more bolts than the rear head; these are the smaller bolts right next to the cam gears. The bolts do not need to be loosened very much, especially towards the cam gear end.

What you are doing is loosening the covers that hold the rails that hold the cams to the head. The cams are under some pretty good pressure from the valve springs so the cam wants to pop up and/or rotate depending on the position of the cam gears. The concern here is that if the bolts are too loose and the cam pops up then it may slip a tooth on the timing belt. As long as the bolts aren’t backed way out then this should not be a problem.

The procedure requires a calibrated torque wrench and a user who is familiar with how to use one. I’d tighten the bolts down in sequence in two passes of incremental torque up to the specified torque of 16 lb-ft (front head has additional 4 bolts at 7 lb-ft). Remember, you are tightening the rails that form a bearing with the cam so you want the bolts to have nice equal pressure.

Good luck,

DanO

 

[Larry Bastanza]

DanO,

I see your point, once I reviewed the torque sequence. With that in mind you could loosen one "cam rail", swap the cam plug. Then only slightly turn the bolts in on that rail to get close to the full "installed" position (cam rail bottomed out on the head pedastels, let's say 5 ft.lbs or less), then move to the second cam rail within that head, do the same, then use the sequence in the book to tighten the entire assembly.

I was wondering if you could "cheat" and use the sequence and just skip one cam and do one at a time. Probably best as the book recommneds though

.

The other thing you may want to do is back off all the valve adjusters to limit the pressure on the cams, but you will have to do a complete valve adjustment (using DanO's procedure!)

HTH,
LarryB

 

[DanO]

Originally posted by Larry Bastanza:
...with that in mind you could loosen one "cam rail", swap the cam plug. Then only slightly turn the bolts in on that rail to get close to the full "installed" position (cam rail bottomed out on the head pedastels, let's say 5 ft.lbs or less)...

I think that would be safe as long as the bolts have enough play to allow the holders to be lifted up at the opposite cam…hmm not sure how to explain this one… Basically, if one cam holder is tight then the other cam will have limited play because the cam holders run across both cams (see pg. 6-33 upper left for more detail) so both cams need to have a certain amount of play to allow free movement. Obviously, the bolts opposite can be tighter because they are not lifted as high. I’m not sure if 5 lbs is too much torque on these bolts or not, I would think it would be just fine if the cam is sprung. If the cam is not sprung and the 5 lbs is direct metal-to-metal then I don’t think it allows for enough play to lift the other side freely. It seems that if holders were lifted off the head about 1cm at the plug end and less than 1cm at the t-belt that it would work…but I’m kinda guessing here.

Larry’s advice about backing off the valves is really safe advice. If you think you might screw things up more by resetting all the valve clearances then it may not warrant the additional work However, I think with our interference-type engines, it’s always a good idea to back off the valve clearance as Larry describes whenever doing head work such as this. I guess worst case is the cam could slip on the t-belt and spin a valve into a piston with enough force to bend a valve—I’d suggest this to be very unlikely if not impossible. But, valve damage would certainly be impossible if the valve clearance was backed off all the way.

DanO

the picture below shows how many bolts there are to torque around with. Obviously, the bolts are _way_ too loose for the topic we are discussing. Please note that the bolts go through both the cam holder pipes (what i was calling the "cam rails") and the cam holders. please see SM page 6-33 upper left picture.

edit to include SM page 6-33 reference.

[This message has been edited by DanO (edited 24 February 2003).]

 

[Larry Bastanza]

DanO,

You are correct. The cam "holders" stradle both cams so they must be loosened together. I went back to the manual , after I tried to understand exactly what you were saying. Make's complete sense.

Litesokneecough,

Based on Dan's comments forget my "one at a time" procedure. Loosen all bolts we described in the manual and have the two cams rise together. The cam gear end should stay slighly downward. DanO, make sense??

Thanks,
LarryB

 

[DanO]

Originally posted by Larry Bastanza:
DanO, make sense??

I think we’ve covered all the bases…I hope..except one little thing:

One more thing
(and this is what has concerned me with dealerships performing this procedure w/o removing the t-belt)
parts of the cam holders at the ends (see SM pg. 6-50 left side) come from the factory with Honda Bond. Look at the SM page and note the shaded parts of the cam holders. These will be Honda Bonded together so you may need to pry up the ends a bit to break the seal. Optimally, one would remove both left and right holders, clean off the old HB, reapply HB (and replace the little oil o-ring seal on the t-belt side holder) and then replace the plugs and torque it all down. Unfortunately, this procedure will require the removal of the t-belt and related necessary hoopla. UNLESS someone can figure out how to remove the rail pipes without removing the two center cam holders! Maybe it’s possible but I can’t figure out the puzzle.

I think that one can get away with simply breaking the seal, replacing the plugs and then torquing it down and not worry about cleaning and re Honda Bonding…but I’m no expert here.

DanO



[This message has been edited by DanO (edited 24 February 2003).]

 

[Larry Bastanza]

DanO,

I had originally discussed this with Barney. I will e-mail him about it, since he has done it many times. I will report back ASAP.

I assume the HondaBond is to insure no weepage from the cam holders at the seam. It's funny how some seams call for sealer and some do not.

I noticed for example when MarkB does a trans he Hondabond's the two case halves, as it calls to. Many other transmissions I have done specifically do not ask for a sealer between case halves.

Thanks,
LarryB

 

[I Grok NSX]

Thanks Larry, Dano and everyone else for your help. I replaced the valve cover seals along with the round seals for the spark plugs. If that does the trick of stopping the leak, I'll stop there. If the leak is still there, I'll do the fix next weekend and let you know how it turns out.

Thanks again!

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1994 Green-black roof/tan, 5 speed
Do you know of another Green-Black roof NSX?? Please email me if you do.