Timing Belt Advice

[MRM]

Question for the NSX experts regarding frequency of timing belt replacement....

I own a 2003 NSX. I purchased it in January 2014, with 50,188 miles on it. In May of 2014 I had the Timing belt, Water Pump, and spark plugs replaced at 50,600 miles at the recommendation of my Acura Dealer's NXS mechanic. Reason being that the recommended mileage for replacement had not been reached, but the car had gone 11 years without a timing belt replacement.

Today, in May 2023, this NSX has ~56,000 miles on the odo. I lay it up for winter (I live in the NorthEast) and it's not my daily driver (yet).
After 9 years and 5,400 miles should the timing belt, water pump, and spark plugs be replaced again?
Or what would the correct interval be given that the car is on the road 6 out of 12 months and not driven that much?

- Mike

 

[Old Guy]

Or what would the correct interval be given that the car is on the road 6 out of 12 months and not driven that much?

- Mike

"Correct Interval" is open to a lot of factors. Probably the biggest factor is your risk tolerance / risk aversion. If rigidly adhering to the Honda / Acura time and or mileage limits is what it takes to let you sleep at nights then stick to the factory specified limits. Other factors that influence this are how is the car used.

With respect to the water pump, Honda does not have a service interval. People replace the water pump preemptively during a timing belt job because failure of the pump after the TB replacement will effectively force a repeat of the timing belt replacement. If you have been assiduous with following the service intervals for coolant replacement I would be less worried about the pump. Mine is 23 years old. I have a new pump in a box and will replace it at the next TB service. At 9 years your pump would not be a must do priority for me if you keep the coolant in good condition. I might be more concerned if you are still running the original thermostat because they do have a slight reputation for becoming leaky which slows the warm up cycle.

The spark plugs I would probably change if the car has been subject to a lot of short duration trips or going through a lot of engine start cycles. In this particular case I err on the low risk side because spark plugs are lower cost items and it is fairly easy to do yourself with minimal mechanical skills. That has nothing to do with being absolutely "correct". Its more about easy to do and low cost - like replacing your air filter a little earlier than the recommended interval.

The TB is a hot button item. As a point of reference, I do not recall any post on NSX Prime of an in-service failure of a timing belt on a car that was not in track use. I believe that you will find that that there are more reports of engine damage / problems caused by badly done TB jobs - a factor to be considered when it may be difficult to find an experienced NSX mechanic. All of this is based upon Prime posts that I have seen which is admittedly not a statistically valid sample set. There have been reports of timing belt damage caused by other factors such as the harmonic damper failure.. If you search on Prime you should be able to find photos of TBs that have been replaced and they all look remarkably new. As a basic observation, your first timing belt went 11 years so you have some basis for extending this one out to at least 11 years.

All of this should reflect how you use the car. If this were a vehicle that gets heavy track rotation where the engine components are subject to a lot of heat then the Honda recommended service intervals are probably too long. Since you appear to be closer to the garage queen driver category (where I am) in a moderately cool climate, I would be more flexible on the TB interval.

 

[Honcho]

Adding to the excellent advice above:

Timing Belt

"Failures" on the NSX aren't in the form of a snapped belt. It's a slipped cam gear tooth. The culprit is a loss of tension in the belt over time. I have personally handled 20+ year belts, even with low miles, that were "floppy" on the car. Meaning they were still in place, but were extremely loose between the rear exhaust cam and the tensioner. Under these conditions, a rapid acceleration or deceleration in engine speed could cause the belt to slip a few teeth. Depending on the amount of slippage, it could cause a valve-to-piston contact. Indeed, many NSXs have shown one tooth off during an overdue TB job.

Water Pump

The main concern here is the internal bearing. Compared to the TB, the main problem is when the car sits for a long time and does not have the coolant changed at the proper interval (3-5 years depending on coolant concentration). The water in the coolant system will corrode the pump impeller and this corrosion will get into the bearing. The risk is that the bearing will seize, though I've never seen it happen in the NSX.

This said, my general rule of thumb for the TB/WP service is every 10 years. If your NSX is heavily tracked in hot weather, I'd stick to the factory interval (6 or 7 years).

One of the best things you can do for your NSX during the good driving weather is take it on a 30-60 minute highway cruise at 3,000 rpm with a couple blasts into VTEC at least once per month. This will burn off any residual moisture, circulate the hot oil to clean the engine internals, and keep all the mechanical bits in working order.

 

[emac]

23k miles and 22 years on my original TB and WP. Both looked perfect when they came off. However, as Old Guy stated, my risk tolerance was beyond its limits!

Original plugs crapped out about 24k miles, so I replaced plugs and coil packs as I wasn't sure which were bad. All coil packs ended up testing ok, so I will keep them for spares. If you are going to replace the coil packs search for the part number for the "set of six". It was way cheaper than buying them individual.

 

[Miner]

I believe Honda (as well as other car companies) are way overly conservative with the maintenance interval for the timing belt. As noted, under normal circumstances the factory belt will last far longer than the recommended interval.

My first Legend, I changed the belt and water pump at the recommended interval. By the time I sold my ‘02 TL-s, I was changing the oil every 15,000 miles, never changed the fluids and only changed the plugs because the coil packs went bad at 250,000 miles. I sold the car at 275,000 only because i was ready for a newer car. It still ran like a female dog in heat.

Just my 2 cents.

 

[drew]

It seems the replacement interval is all over the place. Kaz states that JP recommends replacement based on use and does not take into account time.

My daily driver LHD I would replace every 9+ years. I bought the car used and when I replaced the belt each of the exhaust cams were off by one tooth (front retarded, rear advanced) and the car ran just fine...it sounded slightly better after I installed the new belt correctly. I put a lot of miles annually on that car and I eventually threw a CTSC on it too. Then I was assigned a company car and parked my NSX at work for almost 5 years. When I replaced that belt last it was a bit "dry" and that is the only remark I could make.

I'm replacing the belt as I type on my toy RHD. The belt is 14+ years old maybe 30k km...so I figure I might as well replace everything as this car is "new" to me. The belt had a like new fresh gripe rubber feel and on TDC the camshafts lined up perfectly with the marks and 5mm lock studs. The water pump pulley would easily turn by hand, which means the belt stretched a bit...but not enough to throw anything off. The tensioner and water pump bearings are rock solid and quiet....so I have elected to keep the existing water pump.

I have installed a Gates timing belt (because we need to encourage such vendors), and the water pump pulley did not turn by hand even with the tensioner in the "far left" position...so there is a difference.

My wife's KB Legend (Acura RL) 3.5 was supposed to have a timing belt done 10 years ago. And she stomps on that thing every chance she gets because SH-AWD is fun....kids tell me to make sure not to get her another car with such torque as they get thrashed around in the back.

If I were in your position I would wait another 10-15 years and go with the JP standard: replace on use and not time. And I wouldn't even concern myself with it.

Though I do wonder if there is some value in retensioning the belt at some point.

 

[docnsx]

it is hot topic for sure and one of personal choice.. I did mine last year interval was 7 years with about 1000 miles on belt.. it sits in climate controlled garage and it may be over kill to do.. but in my opinion worth it ... we spend more money on other things that putting money into this for solely piece of mind is worth the cost.. car is at shop as I type for coolant hoses to be replaced with oem.. I don't think they have ever been done...

 

[MRM]

Thanks everyone. Really appreciate the detailed responses.
I think I'm going to wait a bit to replace the Timing Belt given that my NSX is lightly used, stored for winter, and only has 5400 miles on this current belt.

- Mike

 

[Honcho]

Thanks everyone. Really appreciate the detailed responses.
I think I'm going to wait a bit to replace the Timing Belt given that my NSX is lightly used, stored for winter, and only has 5400 miles on this current belt.

- Mike

I think you'll be ok.

 

[The Kid]

Mine was last done in 2007ish with 28k miles, I’m at 35k and have no intention on doing it any time soon.

 

[docjohn]

 

[q_enzo]

Been researching all of Honcho & Drew posts regarding parts for Timing Belt/LMA/Crank Pulley service, and somewhere I copied Valve Stem Seals (12210-PZ1-004 & 12211-PZ1-004) and Cam shaft oil seals (91213-PR7-A01) in my notes.

Do these need replacing while changing LMAs/Cam plugs? Thanks.

 

[Old Guy]

For a normal timing belt service you would not be doing the camshaft oil seals or the valve stem seals. Valve stem seal replacement requires the removal of the valve springs. On some engines, with the correct tools it is possible to do that without removing the engine from the car and with the head still in place. I am thinking attempting in-situ spring removal on the 90 deg C30 / 32 V6 would probably be a bad idea so unless you are doing major engine work I would pass on the valve stem seals. My 2000 C32 has the later design LMAs so I have not had to deal with that issue; but, I expect the cams are coming out to access the LMAs so replacing the cam seals might be a nice to do while there thing.

 

[asylum]

If you do LMA, then do cam plugs and seals. But if you do not hear any clicking noise and have no leaks, you can postpone that to your next TB service.

 

[Honcho]

Been researching all of Honcho & Drew posts regarding parts for Timing Belt/LMA/Crank Pulley service, and somewhere I copied Valve Stem Seals (12210-PZ1-004 & 12211-PZ1-004) and Cam shaft oil seals (91213-PR7-A01) in my notes.

Do these need replacing while changing LMAs/Cam plugs? Thanks.

As @Old Guy mentioned, you need to remove the valve springs to change the valve seals, so it's only a job that you can do really with the engine out. There are tools to compress the springs (to remove the keepers) without pulling the heads. I would not want to be the guy to try that job with the engine still in the car. Valve seals don't need to be changed until they start leaking. On the NSX, they typically start to drip around 100k miles. The sign is a puff of blue smoke when accelerating. You can also borescope the valves to look for signs of oil on the backs of the valve. My NSX had leaking seals (137k miles). And 17 of the 24 valve guides were worn out of minimum spec. This was on an engine that had 20+ years of regular oil changes and easy AT miles. These cars are just getting old- not much we can do about that.

If the engine is out of the car, I'd consider changing them depending on mileage and age. I'd have the tech inspect the backs of the valves to see if there is any oil dripping down. A set of seals is like $20, so it's more of a labor cost than parts.

 

[whh333]

With past timing belt engines I've had, it seems they allowed tensioning the timing belt at intervals, I could be wrong. These were Single Overhead Cams, not doubles.

Page 6-22 of the Service Manual states

"Never adjust the belt tension on any other occasion than when the belt is removed for belt or parts replacement"

This same page shows how to remove the cam pulley covers and adjust the tension without removing the belt, only requiring removal of the cylinder head covers.

As @Honcho stated above, the belt breaking over time is less of a concern than losing tension.

I am tempted to adjust the tension on my belt using the procedure on Page 6-22. Like many others, it has little mileage but many years on it.

Any thoughts on this would be appreciated.

 

[emac]

Personally, I would leave it alone. When it gets old enough that you are worried about it, replace it.

 

[drew]

I have the same questions on timing belt term adjustment.

Seems easy enough to do, indeed it seems to be intended by the idler pulley implementation.

I'm not a mechanical or materials engineer. So I don't know what I don't know.

So far it hasn't been a problem and failing to do it correctly is catastrophic.

This is probably a @Kaz-kzukNA1 question.

Would be nice if Honda released technical documents after a vehicle hits a certain age.

 

[Spoolinfool]

Your probably okay for afew more years if its been stored indoors and away from extreme hot and cold temperatures. Extreme temperatures do all the degradation to the rubber belt. The kevlar lining in the belt takes many cycles or years to degrade. The timing tensioner does loosen overtime with mileage and the tensioner spring does stretch also. With that said if it had 30 to 40k miles of use I would retension or replace those 2 components ( belt and tensioner with spring) but since you only have 6k miles I would leave it alone unless you hear something out of the ordinary.

 

[Kaz-kzukNA1]

On this occasion, the ‘mention’ feature worked and got the notification from the server.
Thanks for the mention, @drew.

Regarding the tension adjustment…
Personally, I would leave it as long as it was tensioned properly last time.
If not sure and if worried, just carry out the TB/WP service together with all the related parts.

Never had to re-adjust the TB tension before the next Eng Refresh on any NSX unless there was another issue forcing the TB to be removed.

Yes, after years, the TB would be stretched and bit loose but not enough to jump the tooth.
Have seen so many super loose TB because they were not adjusted properly at the last service and not because it got stretched.

There is a reason why the rear exh cam pulley is so heavy compared to all other three ones.

Mine is into the 13th year but only covered just about 40K miles and counting.
Not worried about the TB or the TB tension as I know how well the TB is protected against oil/coolant seepage on our NSX engine.
And always carry out the Eng Refresh by myself so knew exactly how the tension was adjusted last time.

From risk management point of view, re-adjusting the tension using the used parts would introduce unknown factor.
And if doing it with the engine kept inside the bay, it would be much difficult to adjust it properly.
Don’t know how one can take out enough slack without removing the TB lower cover.
The lower cover should be removed.

Unlike the auto tensioner mechanism on other engines, NSX engine relies on the tension spring while keeping each cam/crank pulleys at the specific timing/position.

Once the locking bolt is set, that’s it.
No further change on the adjustment and one would rely on the initial tension until the next TB service.

It doesn’t matter even if the tensioner spring may stretch over the years as it doesn’t change the locked position.
Never checked the spec of the spring after 10 years of usage but would only adjust the TB tension using the new spring or few months old.

Used to change TB while keeping the engine inside the bay but always struggled to remove the TB slack at the rear bank and especially the section between the rear exh cam pulley and the tension adjuster.

Doing the process with the eng/gbox outside of the bay is so much easier and gets steady result.

Another reason to leave it until next time.
Kaz