naiad1: (Default)
[personal profile] naiad1
Somehow I made it this far in life without ever hearing of this thing called a timing belt, until now. Fortunately, I learned about it because [ profile] wotw (of all people) suggested I might need one, not because mine broke. My 2000 Sienna minivan has about 93,400 miles on it. Toyota says I should have replaced the timing belt at 90K. I was planning on driving this van for several to many more years, but had not budgeted for a new timing belt, and spring tuition is due . . . On the other hand, this van will be making a nearly 800 mile round trip in a couple of weeks.

So tell me, auto-wonks, how important is it to replace the timing belt now?

Date: 2010-12-30 02:37 am (UTC)
melebeth: (Default)
From: [personal profile] melebeth
When you find out can you also find out what a timing belt DOES?

<- similarly car-ignorant

Date: 2010-12-30 03:28 am (UTC)
From: [identity profile]
My recollection is that timing belt failure leads to catastrophic engine failure, so it is perhaps not a place to skimp.

Date: 2010-12-30 04:02 am (UTC)
From: [identity profile]
A timing belt controls the timing.

Basically, it makes sure the crankshaft (which is controlled by the pistons) is synchronized with the camshaft (which controls the valves), making sure the valves open and close at specific positions of the crankshaft. In some modern engines (interference design engines), if that timing isn't preserved, the pistons will hit the valves (at high speeds, a lot of times), causing catastrophic (read: hard to repair, buy a new car instead) failure of said valves. The wikipedia article is actually pretty good (

My advice: replace it now. Toyota made a lot of interference engines (this is how I learned this stuff-I had a Toyota, at the time, and asked my then-mechanic about it when the timing belt replacement interval came around), and while I am not sure the Siena is one such, I don't recommend risking it. While replacing it is expensive, having it fail is more expensive. The other choice, as I see it, is a new vehicle. This saves the cost of replacing the belt (by putting it on someone else) but has other downsides.

Date: 2010-12-30 04:36 am (UTC)
From: [identity profile]
Agreed - you -do not- want your timing belt to fail. Now, there's a number of places that always tell you to change your belt. A lot of the 'quick oil stop' places try and do it as an upsell. However, I find that Toyota (and Honda) have their lifetimes fairly well figured out in terms of average wear. If the belt goes, and the engine is running, the car is as good as junked in most cases.

Date: 2010-12-30 12:46 pm (UTC)
From: [identity profile]
What they said, plus avoid the "quick oil stop" places - they're often staffed by underqualified people who may be following incorrect information on fluid type and quantity for your vehicle. One of those places cost me a transmission years ago.

Date: 2010-12-30 03:29 pm (UTC)
From: [identity profile]
What they all said. With an interference engine, a broken timing belt is a four-figure repair bill, and the first digit probably won't be a "1". Have a competent shop (most dealer service departments count, for this purpose) do the job ASAP.

Date: 2010-12-30 04:07 pm (UTC)
From: [identity profile]
Dealer has quoted me $575 for timing belt & water pump. My favorite independent guy quoted $650-700. This makes me suspicious the dealer is going to find a bunch of other stuff wrong that will cost another couple hundred, but I have to take it to the dealer for a recall repair anyway, so that's how I'm leaning.

Date: 2010-12-30 05:45 pm (UTC)
From: [identity profile]
Dealers are trying to bring their prices back to more reasonable these days because they know how much work they are loosing to the independent guys.

Date: 2010-12-30 03:22 pm (UTC)
From: [identity profile]
While you are doing the timing belt get the water pump changed at the same time. Some cars have them attached others not, but because most of the cost is in getting to the part it is more cost effective to change them both at the same time.

If you don't change the timing belt and it dies while on your trip you can freeze your engine and then you own a nice large chunk of metal that doesn't go from point A to point B.

The last car I had to do this on I think I spent between $700 and $900 to get the timing belt, water pump and I think I had the serpentine belt done too.


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