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Discussion Starter · #21 ·
loolks like I am one of the cool kids now (I think). Had the timing belt replaced yesterday with JAE's super belt and feel good about it. Old belt didn't look too bad but still now have a warm and fuzzy feeling about the car. Drove it home and noticed that the belt has a slight whine. Texted Julian and Gonzalo and they assured me that this is normal.

You guys with the blue belt have this whine yes?

My car has had a blue belt on it for a while now and it never whined. Its possible that your tension is just a tad high. It can be backed off a bit with no trouble. :up:
 

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Mike, have you ever adjusted the tension on an Esprit timing belt? I would hardly classify it as "no trouble"....
 

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Hey, no trouble....

It's no trouble at all. As long as the engine is out of the car!

:D
 

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Ha, nope, no trouble when it's on the engine stand! And heck, if you blew head gaskets every 3K miles, like me, you just replace the belt and tensioner every 3k and not worry about it going over time!
 

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Discussion Starter · #26 ·
Mike, have you ever adjusted the tension on an Esprit timing belt? I would hardly classify it as "no trouble"....
It's no trouble at all. As long as the engine is out of the car!
:D
OK guys - bad choice of words. What I meant was that is was a correctable condition. Didnt mean easy, just correctable. :)

And the engine does NOT have to be out of the car to replace and or service the timing belt. Easier? Yes. But, taking the engine out comes with its own set of caveats and "better watch its". Im blessed with a small, light, friend with long arms and small hands. He'll be getting in there when we do my major and the plan is to do it with the lump in-situ. ;)
 

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I've replaced my share of timing belts and rebuilt a few engines as well. And, no, the belt can be adjusted "in situ" as our Brit comrades like to say.... The issues with the adjustment are (as noted) the access is not easy and the locking system on the tensioner (I use a specially ground-down box end to move the tensioner so I can also put the 17 mm socket on the lock nut) is tough in that turning the nut to lock down the adjustment can also turn the tensioner itself. Another issue is the sensitivity of the tensioner itself. VERY tiny rotations result in big changes in belt tension. A much nicer system is the more frequently seen use of a tensioning bolt which drives against a movable assembly (a la my Nissan pick-up truck). I understand Elans used such a system though I never worked on an Elan. Lastly, fiddling with tension if you are working solo requires constant getting under the car and getting up and checking the belt, and that goes on until you get the tension dialed in.... much better to have two people - one to move the tensioner and one to check the tension.
 

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Discussion Starter · #28 ·
I've replaced my share of timing belts and rebuilt a few engines as well. And, no, the belt can be adjusted "in situ" as our Brit comrades like to say.... The issues with the adjustment are (as noted) the access is not easy and the locking system on the tensioner (I use a specially ground-down box end to move the tensioner so I can also put the 17 mm socket on the lock nut) is tough in that turning the nut to lock down the adjustment can also turn the tensioner itself. Another issue is the sensitivity of the tensioner itself. VERY tiny rotations result in big changes in belt tension. A much nicer system is the more frequently seen use of a tensioning bolt which drives against a movable assembly (a la my Nissan pick-up truck). I understand Elans used such a system though I never worked on an Elan. Lastly, fiddling with tension if you are working solo requires constant getting under the car and getting up and checking the belt, and that goes on until you get the tension dialed in.... much better to have two people - one to move the tensioner and one to check the tension.
Good info. We will definitely have two guys doing this. We also have access to a good ramp/lift system that will get the car safely offf the ground a good 3 feet or so. We also are going to attack this slowly and be careful :)
 

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Im blessed with a small, light, friend with long arms and small hands. He'll be getting in there when we do my major and the plan is to do it with the lump in-situ. ;)
Could you introduce me to this guy? My Elise could use some work.
 

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I just had to adjust the belt tension last week. I did it mostly from above, only getting underneath to rotate the crankshaft.
I removed the alternator and was able reach everything from above. I also have a box end wrench ground down just for this purpose.
Frank
 

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:bow:

Good point on the alternator. Very true that getting the alternator out of there (and the alternator belt) increases access. If I had to do the tensioning solo I think I would go that route as well,
 

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I also removed the triangle bracket the alternator attaches too for better access.
I can't take credit for coming up with that, I picked that up from Tim Engle. Since I work alone, it was worth the effort of removing the alternator.
Frank
 

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Discussion Starter · #34 ·
:bow:

Good point on the alternator. Very true that getting the alternator out of there (and the alternator belt) increases access. If I had to do the tensioning solo I think I would go that route as well,
Yep - I had read about that alternator deal on The Lotus Forums, I think.

Frank, thanks for bringing it up! It could be a huge time and hassle saver for lots of Esprit doodes. :clap:
 

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Sorry in advance for the abuse of bandwidth. I've posted a file on this subject on the Turboesprit list, but don't think I've addressed it here before.

Lotus 9XX Timing Belts are 133 teeth, 0.375" pitch. The Lotus OEM belts are 26.4mm (1.03937”) wide, but industry standard belts are 1.0" wide (25.4mm). If the belt you buy is not Lotus-branded (Lotus name and part number printed right on the belt), then it will be the narrower width.

*~*~*
TRAPEZOIDAL (sorta-square) Tooth Timing Belt
HCR Rubber (High-Temp Neoprene/ Chloroprene).
HCR = old 1960's-tech materials / shorter service life.

Lotus Change Interval: 24,000 miles / 24 months
(street logic Chg Intvl: 12,000 miles / 24 months).

Functionally, there's little or no difference between those two change intervals. Most Lotus cars don't get driven enough to hit the mileage limit first, and they time out. If they time out first, then it doesn't matter if the mileage spec is 12,000 or 24,000. The real point is that the HCR version is not a long life belt, so do not try to stretch the change interval.

*~*~*
TRAPEZOIDAL continued...
HSN Rubber (Highly Saturated Nitrile).
HSN = newer tech rubber (mid-1990’s) / longer service life
Development of the trapezoidal timing belts stagnated after the superior round-tooth HTD profile was introduced, and they didn’t benefit from any of the newer materials that later went into the round tooth HTD belts. However, JAE has worked directly with Gates Racing to produce HSN trapezoidal belts for the Lotus 9XX engines (907, 910, 911, 912, through 1985). It’s the highest-spec trapezoidal timing belt available for those engines. Contact JAE for details.

The latest timing belt technology uses HNBR rubber (ie, the JAE blue HTD round tooth belt). However, the Gates factory that runs HNBR rubber does not have the tooling for the trapezoidal tooth belt, so there will be no blue HNBR trapezoidal belts for the pre-1986 engines.

*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*

HTD, ROUND Tooth Timing Belt
HTD = High Torque Drive

*~*~*
HCR Rubber (High-Temp Neoprene/ Chloroprene) T188
Lotus A-Prefix part number HTD belt (discontinued).
As noted above, HCR is old 1960's-tech material, and the HTD round-tooth design dates back to ~1985. Of the various HTD belts available, the HCR versions have the shortest service life.

Lotus HCR A-Prefix Change Interval:
37,500 miles / 36 months

*~*~*
HSN Rubber (Highly Saturated Nitrile) T249
Lotus B-Prefix part number HTD belt (current).
The HSN HTD round-tooth Lotus B-Prefix belt was introduced in 1995, and was the standard service replacement from that point onward. The previous A-Prefix HCR belt was officially discontinued at that time.

Lotus HSN B-Prefix Change Interval:
50,000 miles, excluding California
100,000 miles in Calif - by law, not by Lotus' choice.

Lotus never said the HSN belt was good for 100k miles, and California didn't mandate that the belt must actually last 100k. California simply mandated that all manufacturers must warranty the belt at their expense for 100k miles, or they could not sell the cars in California. So Lotus warrantied the belt, required more frequent inspections in the Calif-only Service Schedule, and provided free replacements at shorter intervals (usually 50k miles) as indicated during scheduled services.

Any Calif owner of a 1995-onward 4-cylinder Esprit for which the warranty has expired (all) should absolutely NOT be thinking they have a 100k mile belt on their engine. They DO NOT. Nor do they have the back-up of a warranty to pick up the cost of an engine rebuild if it breaks. California emissions maintenance is a whole different subject; but, from a mechanical maintenance standpoint, California owners should adopt all aspects of the non-Calif Service Schedule once the factory warranty has expired. !!!

*~*~*
The old-tech HCR HTD belts continue to be sold aftermarket as an “Economy” belt. If the price is just too good to be true, the belt is probably HCR. Use an HCR belt if you must save a dime (bad idea IMHO), but don’t delude yourself into thinking it’s as good as the HSN, and do not consider running the HCR for the longer change interval specified for the Lotus B-prefix belt.

If the belt on your engine is black, but you don't know if it's HCR or HSN, then the only safe assumption is that it's HCR and replace it on the shorter schedule.

*~*~*

HNBR Rubber (Hydrogenated Acrylonitrile-Butadiene Rubber)
There is no such Lotus OEM belt or part number.
JAE blue belt only.

HNBR was introduced to the industry in ~2007 as the next evolution, but the 9XX 4-cylinder engine was long out of production by then and Lotus was no longer supporting it with on-going development. Therefore, there is no Lotus HNBR HTD timing belt, there has been no official development work to determine a revised tension spec for the blue HNBR belt, nor dyno/ road testing to determine an official change interval. Lotus has no involvement with the blue HNBR belt.

The HNBR belt technology is the best currently on the market (2013), the belt should last longer than the previous HSN technology, and it should be more stable (not require re-tensioning as often). The HNBR belt should be considered an upgrade, and a good thing for both 4-cylinder and V8 Lotus 9XX engines.

However, any assumptions about proper tension requirements, and change interval are left to the owners. It will be our combined grassroots experience with the belt, and JAE's feedback experience without testing, that will set the specs for the blue Gates Racing HNBR belt. And no, running the belt until it breaks is not a good way to determine a change interval (covering your ears and tapping with your foot doesn't make a good mine detector).

*~*~*
JAE Blue Belt Change Interval:
My thoughts only, no warranty, use at your own discretion.

Historically Lotus belts generally went about half the expectancy of normal "civilian" automotive applications. The HSN target (mandated) was 100k miles, and Lotus went 50k outside California. The new HNBR is supposed to be the belt to meet the government mandated 150k service interval, so I'm thinking 75k MAXIMUM in the 9XX 4-cylinder engines (ears covered, tapping foot). BUT...

For a typical Lotus, 75,000 miles will take a very long time. Heck, accumulating 50,000 miles takes a long time. So my personal opinion is to observe Lotus' last Change Interval of 50,000 miles, and bank the HNBR belt's expected superior performance as an insurance policy. There is no Lotus warranty in effect for the 9XX 4-cylinder engines, so spend an extra buck on a superior belt on the standard schedule as a way of staying out of trouble. That's my recommendation.

*~*~*
Tension:

The Lotus recommended tension gauges (the Borroughs and Clavis Frequency Meter) are sensitive to changes in the belt itself.

The Borroughs' reading changes with belt thickness and stiffness, and the blue HNBR belt is both thicker and stiffer.

Any taut strand's frequency response (guitar string or timing belt) varies with the strand's weight and stiffness, and the blue HNBR belt is stiffer and heavier (and the HTD is thicker and heavier than the trapezoidal).

Even if you use the Borroughs or Clavis according to Lotus' old procedures, they will not produce the same linear tension in the blue HNBR belt that Lotus originally intended when the specs were written.

In my limited experience with the blue HNBR belt, if you set the tension to 95 on the Borroughs gauge, the belt will run with a pronounced whine. A belt that whines is usually telling you it's too tight. IMHO, I prefer to set my black belts a bit on the tight side, and sometimes do hear a hint of a whine. But the blue belt at Borroughs 95 isn't hinting... it's whining. IMHO, that's too tight.

Backing the tension down until the blue belt no longer whines, gets it down to about Borroughs 80. Okay, maybe I'm an out of date dinosaur, but 80 tension in a 9XX belt just makes my skin crawl... IMHO it's too loose. I have no particular engineering insight to the HNBR belt, but I won't set one to Borroughs 80 on any 9XX engine I work on.

Borroughs 90 is the lowest tension Lotus ever recommended for an OEM black belt, and using that tension on a blue HNBR belt produces a slight whine... a whine that tends to fade with time as the belt beds in. Since my normal MO is to set the belt a wee bit tight anyway, I'm more comfortable with 90 and a hint of a whine than I am with either 80 or 95.

I have not yet set a blue belt to Borroughs 90 at TDC, and then taken a frequency reading at 30 BTDC, so I have nothing to offer those of you using a Clavis, or a frequency analyzer AP on your PC or smart phone. However, vibration theory dictates that 100-110 Hz on the blue belt will result in it being too tight/ whining. Just my thoughts.

*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*

Servicing the timing belt -- Change Interval Synopsis:
Miles / Months
6,000 ............ Check tension. Re-tension only if required.
12,500 ............ Check Timing Belt Tension / Adjust as required
12,500 ............ Inspect Timing Belt condition
12,500 ............ Inspect Tensioner Bearing / replace as required.
12,500 ............ Inspect valve timing (dot alignment on pulleys)
12,500 ............ Check valve clearances, adjust (shim) as required.
37.5k / 36 mo, Adjust valve clearances, required

Trapezoidal tooth timing belt…. service interval
24.0k / 24 mo, replace trapezoidal timing telt, required
12.0k / 24 mo, street logic, replace trapezoidal belt.

HTD, ROUND tooth timing belt service intervals
37.5k or 36 mo, replace A-Prefix, HCR, HTD belt
50.0k, (no time spec), replace B-Prefix, HSN, HTD
100k, California warranty requirement only, IGNORE.

50.0k, (no time spec), IMHO, replace JAE blue belt.
75.0k, Maximum IMHO, replace JAE blue HNBR.
I strongly suggest using the 50,000 mile HSN change interval, and banking the HNBR belts greater durability as an insurance policy.

Where no time limit was specified, DO NOT let any belt get old. I think 5 years is old, but that's just my opinion.

I talked with an engineer at Lotus, and he said they're totally amazed that the Esprits are being preserved as much as they are, and that mileage accumulates so slowly... especially in North America. In England, owners tend to drive them more like cars, use them up, and move on.

He emphasized that Lotus' timing belt mileage specs never anticipated that it would take soooo freaking long to accumulate those mileage numbers, and that plain old age IS important. DO NOT consider a 50k mile spec with no stated time limit to be an open-ended ticket on your low mileage S4/ S4s' timing belt... it is NOT. If you own a low mileage Esprit with an original timing belt on it, then it's scary waaaay past due for replacement... you're on borrowed time.

Regards,
Tim Engel
Lotus Owners Oftha North
 

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Hi Tim:

Thanks - that was a GREAT article to read while on my lunch hour! I never knew the early technical history of the belts. A bit surprised to see the short replacement intervals for the early belts.
 

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Discussion Starter · #37 ·
Tim - as always, thanks for teaching us mere mortals about this stuff. Great post and info. :bow:

So, in my case with a blue belt, water pump & new tensioner in 2009 and about 23K miles on them.... am I still good for at least this driving season and maybe do it next spring? Just curious - I know your answer doesnt come with a warranty :)
 

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My vote is to play it "conservatively aggressive" and do it in the fall. That would be just about 4 1/2 years. Plus, if unexpected issues come up and it takes us longer than we planned on, by doing it in the fall you aren't losing the beginning of the driving season.
 

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I see the Gates T249 belt gets referenced quite a lot. Something to bear in mind is that this is not just a Gates T188 belt made using HSN rubber, the tooth profile is different too.
 

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Removing the alternator in my own oipnion is a waste of time. To save the hassle I'll climb under the car and adjust the tensioner. Plus I get plenty of :mw:

Jim is right, it's not a fun job. Someone else mentioned when you tighten the tensioner {Tom?} without holding the eccentric that it will change the tension which is true. I hold the eccentric nut in place with a wrench, then with another wrench I tighten the lock nut down. If you don't do that when the lock nut is tightened down it will throw off your reading as the eccentric bearing spacer moves.

I've seen most tensioners usually start to get raspy at 70k. Anything over that is taking a chance. The bad batch of Volvo one's we had was the first time in my 25 years of turning wrenches I ever saw that happen.

In high output manufacturing 'Quality Control' doesn't inspect every part, they will pull one from a hundred or more. They are made with 'batch numbers' so if one fails they can trace it back to that batch. If one failed it's highly possiable there could be other bad apples out there, which in this case there was.
 
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