Head cover gasket mandatory with timing belt ?

[asylum]

Simple question : is it mandatory to remove the head covers (and then replace the head cover gaskets) to replace the timing belt ?

I am asking that, because my two NSXs do not make a lot of miles between two timing belt replacements and are stored in a dry heated place. So I do not want to make excessive / unuseful maintenance. For example : is water pump do be done every 6 - 7 years if less than 10k miles have been done or is it a no brainer to let it for another interval ? This is what I do for the cooling hoses. I replaced them 6 year / 6 kmiles ago and I only plan to change them in 6 years.

For a little used, garage kept NSX, can we asume this is enough :
Every 6-7 years : timing belt & tensioner
Every 12 - 14 years : timing belt & tensioner, water pump, crankshaft pulley, ac & accessories belts, cooling hoses, headcovers / camshafts / solenoids seals & gaskets.

 

[goldNSX]

Heat cylces and mechanical stress are the keywords here.

I guess these are DIY projects? It's hard to recommend a different interval than Honda states, I don't want to be guilty if sh*t happens but that's what I do with my car which is been driven on the street only for 3-6k miles/year.

- TB complete program every 10 years which includes WP, all seals, valve adjustment etc.
- coolant hoses every 15 years
- coolant every 7.5 years -> Honda stuff only

I recall that you bought your street car with the TB being done in January of the year you got've it. But the TB wasn't changed for 20 years til then. Not sure about the WP. It was an all-round garage who did the job. Their reputation is good but they're not NSX-experts and they didn't ask me a single question even though I offered them my help just in the case. Of course, they don't have to, some kind of Kimi Räikkönen style: "F*ck off, we know what we're doing!" So I'm pretty sure it still has the OEM LMA. Not sure about the pulley shield and so on...

 

[asylum]

On my street car, I have to check the last timing belt replacement report. I think that the water pump has been done. On my race car, it was done with the last TB replacement as well as coolant hoses.

Concerning LMA, did you do the job on your car ? Is it mandatory ? After how many miles do the stock piston device tend to seize ? I only have about 50 kmile (75kkm) on my cars.

And my first question is still open : is it mandatory to remove the head covers (and then replace the head cover gaskets) to replace the timing belt ?

 

[Old Guy]

And my first question is still open : is it mandatory to remove the head covers (and then replace the head cover gaskets) to replace the timing belt ?

If you follow the service manual procedure and use the 5mm pin punches to lock the camshafts in position, that requires removal of the covers. I haven't thought beyond that as in, do I really need to lock the camshafts in position? The gasket replacement is a risk assessment; but, fortunately its a low impact risk. If the reused gasket fails its going to result in an oil leak not a major failure. It then becomes a balance of what is the cost of new gaskets versus the potential annoyance of having to deal with an oil leak caused by re use of the original gaskets.

 

[goldNSX]

And my first question is still open : is it mandatory to remove the head covers (and then replace the head cover gaskets) to replace the timing belt ?

Yes. No way without removing the head covers.

Concerning LMA, did you do the job on your car ? Is it mandatory ? After how many miles do the stock piston device tend to seize ? I only have about 50 kmile (75kkm) on my cars.

Yes and No. LMA means to take the cams out. Did that several times, with the engine out preferred but not mandatory, just easier to work with. Strongly recommend to change the cam seals and cam plugs too at that age. They tend to shrink and get pressed out of their seating. These surely haven't been done the last time on your street car. Bad LMA won't damage anything but the noise can be unbearable. It's not a primar function of the miles driven, it's more or less unknown why they tend to stick.

On my street car, I have to check the last timing belt replacement report. I think that the water pump has been done.

Better check the design of the WP from the outside around the cover. If some kind of a metal drain tube sticks out of the cover by about 5 mm it's the later design and must have been replaced in the past. My strong guess is that it hasn't been changed. Same for the coolant. Post a picture here.

 

[Old Guy]

- TB complete program every 10 years which includes WP, all seals, valve adjustment etc.
- coolant hoses every 15 years
- coolant every 7.5 years -> Honda stuff only

I am also on a 10 year cycle for timing belt replacement. The car is a 2000 and the water pump was not replaced when the timing belt was done in 2010. I will plan for replacement of the water pump in 2020 because my gut based non quantified risk assessment says that the probability of the pump failing prior to 2030 (next planned timing belt replacement) is probably going up. If this was an engine from the 1960 /70s and you could do a pump replacement in 90 minutes with a coffee break, I would wait for the pump to develop a leak and replace then (I have never had a pump fail catastrophically). Since a water pump replacement is effectively a timing belt replacement on the NSX, that moves the impact level up several notches on the risk assessment meter.

The coolant hoses are all 20 years old and the ones that are easy to inspect look to be in excellent shape. I will probably replace the hoses to the oil cooler (because they get exposed to oil) and the three hoses to the head because that is the only location that I have ever read a post mentioning hose failure (during a track session).

Your coolant replacement cycle is quite extended compared to the recommendations in the NSX service manual. Honda (North America) recommends 3 year intervals for the first two changes and every 2 years there after. Its not obvious to me why you need to switch to 2 year intervals after the first 6 years of ownership. I am closer to the 3 year interval, likely stretched to 48 months depending on when the water pump & TB is done next year.

 

[Honcho]

On my street car, I have to check the last timing belt replacement report. I think that the water pump has been done. On my race car, it was done with the last TB replacement as well as coolant hoses.

Concerning LMA, did you do the job on your car ? Is it mandatory ? After how many miles do the stock piston device tend to seize ? I only have about 50 kmile (75kkm) on my cars.

And my first question is still open : is it mandatory to remove the head covers (and then replace the head cover gaskets) to replace the timing belt ?

Agree with [MENTION=10201]goldNSX[/MENTION] on all. You MUST remove the valve covers to do the timing belt job because you need to access the cam gears to remove and install the belt, as well as referencing the timing markings. According to Kaz, the valve cover gaskets CAN be re-used if they are recently new. But, after a time the rubber will take a set and not "squish" anymore, which will result in oil leaks. How long depends on running conditions, i.e., operating temperatures, humidity, ambient temps, heat cycles, etc. Personally, I would say if they are older than 6 months, you should replace them. The cost is fairly low. As for LMA, it is a "when" problem, not "if." Due to the design, all of your LMAs will eventually stick. This is why Honda updated the design to a simple spring and superseded the old part for use on all NSX models. Like the gaskets, the time limit depends on usage conditions.
As gold noted, it's not really dangerous for your engine (perhaps accelerated wear?), but the noise can be bad, depending on how severely they are sticking.

 

[Honcho]

I am also on a 10 year cycle for timing belt replacement. The car is a 2000 and the water pump was not replaced when the timing belt was done in 2010. I will plan for replacement of the water pump in 2020 because my gut based non quantified risk assessment says that the probability of the pump failing prior to 2030 (next planned timing belt replacement) is probably going up. If this was an engine from the 1960 /70s and you could do a pump replacement in 90 minutes with a coffee break, I would wait for the pump to develop a leak and replace then (I have never had a pump fail catastrophically). Since a water pump replacement is effectively a timing belt replacement on the NSX, that moves the impact level up several notches on the risk assessment meter.

The coolant hoses are all 20 years old and the ones that are easy to inspect look to be in excellent shape. I will probably replace the hoses to the oil cooler (because they get exposed to oil) and the three hoses to the head because that is the only location that I have ever read a post mentioning hose failure (during a track session).

Your coolant replacement cycle is quite extended compared to the recommendations in the NSX service manual. Honda (North America) recommends 3 year intervals for the first two changes and every 2 years there after. Its not obvious to me why you need to switch to 2 year intervals after the first 6 years of ownership. I am closer to the 3 year interval, likely stretched to 48 months depending on when the water pump & TB is done next year.

I'd be careful with the hoses. I know of 2 cars that had failures of the two main hoses to the radiator (one was at the track, the other was driving along on the highway). One of those cars twisted a head due to the overheat. The problem with visual inspection is that you cannot see the state of the nylon braids inside the rubber- these typically become brittle and no longer reinforce the rubber. The cost of the replacement hoses is fairly low (around $400 for the entire set) so I would replace them all. Once every timing belt is probably overkill, but I would say every 15 years. Less if it is a track rat. I would be more relaxed about it on a different type of car, but the NSX is sensitive to overheats- the heads will warp rather quickly in a loss of coolant event.

Kaz had an interesting post on his blog where he pulled the water pump out of a NSX that had been recently replaced, but where the car sat idle most of the time and was barely driven. The impeller was corroded and there was already slop in the bearing. He concluded that it was sitting for long periods of time and not running miles, that contributed to the early deterioration of the pump. This would explain why there are some NSXs out there with well over 100,000 miles running on their original water pumps with no issues. I think you are smart to replace it in 2020!

 

[MotorMouth93]

I've reused valve cover gaskets when they're relatively recent but getting the old Hondabond off the corners of the gasket is a massive pain in the butt.

 

[goldNSX]

If this was an engine from the 1960 /70s and you could do a pump replacement in 90 minutes with a coffee break, I would wait for the pump to develop a leak and replace then (I have never had a pump fail catastrophically).

Plus with the non-interference engine you could even wait for the TB for fall apart but TBs were not that common back these days. Good old times.

The coolant hoses are all 20 years old and the ones that are easy to inspect look to be in excellent shape. I will probably replace the hoses to the oil cooler (because they get exposed to oil) and the three hoses to the head because that is the only location that I have ever read a post mentioning hose failure (during a track session).

I've heard and read about all main hoses to be at risk, at the radiator, under the car, to the engine. The oil cooler hoses are not exposed to oil (unless there's a leak from the rear valve cover) but they do get hot. The high operation pressure of up to 1.1 bar makes the big hoses pretty hard. That + heat adds up to the stress on the coolant hoses. Whenever the inner structure of the hoses collapses the hose bursts. There are no warning signs to be observed in advance. Every 15 years is quite an intelligent change interval. Hot climate and high stress (track) every 8-10. Whenever I've pulled the old main hoses off I could hear the structure being stressed but I was much younger back then.

Just saw that Honcho responded to the coolant hoses. So my info is kind of stressing the importance to not neglect them.

I've also seen a car with a corroded impeller of the WP. I don't know it's history. The corrosion was not only on the impeller but also on the tube which is not nice to have. Just another argument to let it run every month during a long storage time.

Your coolant replacement cycle is quite extended compared to the recommendations in the NSX service manual. Honda (North America) recommends 3 year intervals for the first two changes and every 2 years there after. Its not obvious to me why you need to switch to 2 year intervals after the first 6 years of ownership. I am closer to the 3 year interval, likely stretched to 48 months depending on when the water pump & TB is done next year.

I know but Honda OEM coolant is not easy to get by here and I haven't observed any ill effects so far. If I were in the US I'd change it more often I guess. But I'm still on the safe side compared to any other NSX here in Europe.

 

[goldNSX]

Hi Sylvian

As far as I've seen you have all the nice ingredients in your garage to pull the engine from the car and do a complete TB job.

 

[asylum]

I have had the lower radiator hose failing at the track 7 years ago. That is why coolant hoses were on the list when we did the timing belt. Now they are 7 years old so I do not plan to to them during the next timing belt change next year. On my street one, they are on the list because I am sure they are 28 years old. I hope none will fail before the next TB change in 4 years.

 

[Old Guy]

Kaz had an interesting post on his blog where he pulled the water pump out of a NSX that had been recently replaced, but where the car sat idle most of the time and was barely driven. The impeller was corroded and there was already slop in the bearing. He concluded that it was sitting for long periods of time and not running miles, that contributed to the early deterioration of the pump. This would explain why there are some NSXs out there with well over 100,000 miles running on their original water pumps with no issues. I think you are smart to replace it in 2020!

That is an interesting observation. It would reinforce my 'rust never sleeps' theory. Once wet and if exposed to O2 and nasty chlorides and other stuff in the air (including entrained air in the coolant) corrosion is going to start regardless of use patterns. Filling with new coolant and parking is probably not the best practise because the act of refilling the cooling system is going to result in dissolved air in the coolant. The act of heat cycling and mechanical agitation of the coolant through engine use should remove the entrained air in the coolant reducing the risk of corrosion.

If the pump that Kaz mentions was recently replaced and corrosion had already set in I would be extremely suspicious about the coolant chemistry. It seems like the corrosion inhibitors must have been a little sub par (depending on how long 'recently replaced' was) or the owner did a coolant / water mix using highly oxygenated water and then parked the car without going through the heat cycling and mechanical agitation necessary to remove the dissolved O2.

I have had a number of pump failures (all European cars) and the pump failure has always been the bearing or seal failure, typically caused by excessive side loading. Corrosion of the impeller was never an issue, at least before the bearing failed!