Timing Belt Interval

[92saturnsl2]

Do manufacturers normally factor in a margin of safety in their timing belt replacement intervals?

My VG33ER Frontier (2001) recommends replacement at 105k. It'll probably be at 110k or so before I am able to replace the belt as I have a lot of driving to do early in the year and no time to take the vehicle in for service. Is this safe or am I asking for trouble since this is an interference engine?

 

[simple_gifts]

Of course there is a safety margin; consider 105K of city driving vs 105K of highway;

However, there may be a time limit imposed also.....

I would get it changed sooner; else you will have 5K miles of stress.

 

[hate2work]

Well, they might factor in a margin of extra time. But what does that mean in the real world?

I have seen timing belts ready to shred at 70k miles, and others that still look decent at 100k miles.

Is this an interference engine? If it is, the valves will hit the tops of the pistons if the belt breaks while you're driving. You don't want that to happen.

Pay the extra money and get an OEM belt, the aftermarket ones are not the same quality. And get it done sooner than later.

 

[rpn453]

The manufacturer recommended interval should be a very safe interval, so I wouldn't worry about an extra 5K miles if it were my vehicle. You'd have to check vehicle specific forums to know for sure how safe that interval is. The 3.3L '98 Pathfinder I had a couple of years ago recommended timing belt replacement every 105K miles with no time limit. I could find only one person on the NPORA forum who had suffered a broken timing belt on that design, and IIRC he was at 252K miles on the original belt when it happened. Obviously he was doing a lot of highway driving.

 

[ChiTDI]

I think the real issue is whether it is an interference engine or not.

 

[moribundman]

Originally Posted By: 92saturnsl2
Do manufacturers normally factor in a margin of safety in their timing belt replacement intervals?

My VG33ER Frontier (2001) recommends replacement at 105k. It'll probably be at 110k or so before I am able to replace the belt as I have a lot of driving to do early in the year and no time to take the vehicle in for service. Is this safe or am I asking for trouble since this is an interference engine?


The belt may actually be not the main source for concern. Depending on the vehicle, a belt tensioner, and idle roller, or a water pump may fail, which in turn will cause the belt to skip a couple teeth or to break. Always make sure those critical parts, if applicable, are replaced along with the belt.

As far as the belt itself goes, I propose time to be more of a factor than miles driven. 100k miles or 5 to 7 years seems a reasonably safe service life for most timing belts.

If the car manufacturer suggests a TB change every X miles or every X years, I would stick to that recommendation.

 

[92saturnsl2]

Thanks for all the input. This is an interference engine, so I realize the importance of changing on time.

From the Frontier forums I've seen, I only remember one case of a timing belt breaking, which was the original at 150k, but I distinctly remember something else contributing other than normal wear.

The belt doesn't turn the water pump, but the pump is in an area where it'd be possible to get coolant over the timing components in the event of a failure.

I was just curious as to the frequency of belts breaking near the maintenance interval... Is this a routine occurrence, or do the manufacturers always specify intervals conservatively?

 

[moribundman]

Originally Posted By: 92saturnsl2
I was just curious as to the frequency of belts breaking near the maintenance interval... Is this a routine occurrence, or do the manufacturers always specify intervals conservatively?


The following is my opinion and does not necessarily represent fact:

I believe that manufacturers estimate the service life of the TB conservatively with a fairly large safety margin. I also believe that neglecting maintenance (regular inspection of the belt and of critical components) can render this safety margin nil.

 

[Kestas]

Incredibly, I ran my 85 Omni for 165K and sold it before I ever knew that timing belts were a wear item! This car was my first timing belt car, so I had no idea they needed periodic replacement. I always read the owner's manual of every car I own, and there was nothing noted by the manufacturer that the timing belt would ever need to be changed. None of my gear-head friends ever mentioned it either. I guess I was lucky.

 

[moribundman]

Did that Omni still have the VW engine?

 

[Tornado Red]

Originally Posted By: hate2work
Pay the extra money and get an OEM belt, the aftermarket ones are not the same quality. And get it done sooner than later.

What is an OEM timing belt? Auto manufacturers do not make timing belts, they buy them from Gates or Conti or Dayco or another reputable supplier. You can do the same.

 

[PT1]

Get the Gates belt or the Conti. Dayco MarkIV is having serious quality problems. Gates makes the best belts. But I would not worry about the extra 5000 miles on that belt...just because your valves will go slamming into the pistons and explode into a red hot metallic shower inside the cylinder heads leaving you stranded wherever you may be. I wouldn't give it a second thought....

 

[Whimsey]

Originally Posted By: PT1
Get the Gates belt or the Conti. Dayco MarkIV is having serious quality problems. Gates makes the best belts. But I would not worry about the extra 5000 miles on that belt...just because your valves will go slamming into the pistons and explode into a red hot metallic shower inside the cylinder heads leaving you stranded wherever you may be. I wouldn't give it a second thought....

Well I changed my timing belt and tensioners in my '96 Zetec Contour at 12 years and 70,000 miles. The belt looked ok but like PT1 I didn't want a "red hot metallic shower inside the cylinder heads....

. I'm keeping the car so it's cheap insurance for me. I had the Ford dealer do it and hopefully they used Motorcraft parts. They charged me for Motorcraft parts!

Whimsey

 

[JHZR2]

A friend has an 02 GTI with a lot of highway mileage. 148k and no timing belt change ever.

He does run M1 0w-40, and his engine is clean, so that's a plus.

 

[JHZR2]

Originally Posted By: PT1
Gates makes the best belts.


Does Gates make the best belts because youre from the "Rubber City" and they sign your paycheck?

Is there a way to guarantee that youre getting a gates belt? I dont know offhand what auto parts stores sell gates...

Thanks!

 

[Tornado Red]

Originally Posted By: JHZR2
Is there a way to guarantee that youre getting a gates belt? I dont know offhand what auto parts stores sell gates...

You can ask. Or you can look at the belt yourself

 

[bdcardinal]

Originally Posted By: Whimsey
I had the Ford dealer do it and hopefully they used Motorcraft parts. They charged me for Motorcraft parts!


i can guarantee they didn't use Motorcraft parts as timing belts are Ford OEM, not Motorcraft currently.

 

[dhise]

This is probably somewhat dependent on the engine design as well. My subaru ea82 was their first timing belt motor with 60k belt replacement intervals. Pretty accurate since they do break within a mile or two after 60k!

 

[92saturnsl2]

It's interesting that after doing a bit more research, there are several documented cases on the web of the belts breaking on this engine. All but one were well after 140k. Furthermore all but that same one suffered no engine damage, there was no interference at all between the valves and pistons, there are even valve reliefs cut into the pistons.

So I guess there is no hard evidence that this is actually an interference motor. Since the VG33ER has much lower compression (8.9:1 IIRC) than the VG33E, it would be even more likely that this isn't an interference design. Just some food for though, I don't anticipate stretching the interval too far.

 

[VK56VD]

If you intend to keep this vehicle for a while, I wouldn't skip on changing the TB. Use a Nissan OEM or another high quality belt as suggested by others.