The drawback to gear-driven camshafts is that gears tend to be noisier than chains or belts, and implementation would require more lubrication. In engines with overhead camshafts, multiple gears would be needed due to the distance between the crankshaft and camshafts.
A magnetic coupler is an interesting idea, perhaps the barrier to implementation is that the magnet would have to be fairly large to drive the pump.
Dealership and independent service departments generally use a retail labor time guide like Mitchell, Motor, Chiltons, etc. to look up the labor times for a particular labor operation. They are supposed to look up the labor time for the deepest operation, and then look at the chart for any add-ons, like replacing the water pump along with the timing belt. As for the 50 or so Toyota dealers I've visited, none charged extra labor for accessory drive belt replacement when changing the timing belt.
I do remember the old push-rod engines would 'float' their valves if you over-revved them. It would often result in bent valves or cracked pistons. Miss a shift and you got an expensive lesson in performance shifting.
Jack
Driving the water pump from the timing belt is now the rule, rather than the exception.
Ahh! There you go. So maybe they were in fact interference, but since we didn't have timing belts to break, the average driver wasn't forced to be aware of it. But yeah - now that you mention warnings against floating the valves, that does have a familiar ring to it.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
What makes you believe that?
Where do you come up with three?
(It's called Phat Phingers...)
This is for a '98 Camry:
Don't drink so early in the day, eh?
All the early Hyundais I saw, starting with the Pony in Canada, had engines either licensed from, or based on Mitsubishi engines, and IIRC all Mitsu engines are Interference...
But they do charge the full labor rate when replacing the water pump at same time as timing belt change, even if the customer pays full rate for a timing belt change.
Hmmm...the tech at the Chrysler dealer owned by the Toyta dealer I worked for said Interference...
At any rate, it's gone noe...I traded it for $600 towards a Scion tC I bought.
For $600 I should have kept it. It was mint!
Must have done a lot more than head damage.
That wasn't a dealer! That was an independant Subaru 'specialist' who everyone tells me is the best.
Must have had a boat payment due. Or, coome to think of it, it *was* just after Christmas...
The labor rate does not change when adding additional work unless the dealership uses variable labor rates depending on the difficulty of the operation, where they charge a lower rate for simple work like changing oil, a slightly higher rate for moderately difficult work like changing a timing belt, and the highest rate for complex work like diagnosing a drivability or intermittent electrical problem.
In the case of a Camry water pump and timing belt replacement, replacing the water pump is the deepest operation, so they would have charged the customer for the labor to replace the water pump, plus an extra half hour or so to replace the timing belt.
Not according to a lot of people who post in this newsgroup. They report that the dealer quoted them full price for both procedures, even when done together.
Dunno.. I'd always want to change the WP and tensioner if I'm in there doing the belt. Delaying the pump in particular is just not worth the risk of damage to the engine, and also you'd have to go back in there. I always recommend doing it all and being done with it. Oil seals too.. But.. I do it myself... Changing a timing belt is easy. But... You have to be very exact in setting it back up. You can't even be one tooth off. This is not hard to do, but it's not unusual to have to redo it
2-3 times before finally locking it all down. I'll align the marks before removing the belt making sure they are perfectly aligned. When I put the new belt on, I make triple sure the marks are *exactly* like they were with the old belt. Never have had any problem.. I'd crank the engine with the new belt, and it would sound the same as with the old one.. You will know if it's even one tooth off. It won't run and time right. It'll feel and sound different right off the bat. If that ever happened to me, I'd tear it back apart and do it over until it was right. But.. I make sure it is right the first time.. I *hate* doing things over. The danger in postponing a WP is they often totally flake out in only a few minutes time. You often get no or little warning before they start squealing, and pouring out water. I don't need that @#$% in my life.. So I alway swap in a new pump if I'm in timing belt territory. And.. I always use at least a new pump if not OEM. Don't get the rebuilts. They suck. But the new ones are ok. Or at least I haven't had any problems with new ones so far. Costs a bit more, but it's worth it. If there is a kiss of death to a JA engine, it's overheating. I'll do anything I can to reduce the likelihood of it happening. Once you overheat one real bad, they ain't never the same again.. :(
The auto mfg's should mount the WP reversed, not attached to the engine block and driven by assy belt. That would make it more accessible and cheaper to change.
Some older cars (and tractors) were essentially done that way. It is exactly opposite of the trend towards more and more integration - adds weight, parts, and up front labor costs. Good or bad, initial cost, weight and compactness trump consumer convenience and life-of-vehicle costs to the nth degree.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
I understand. If real reliability and true low cost ever really becomes important, it could be feasible. Can you imagine a car that you did not have to dump hundreds of dollars and inconvenience every 100k miles on as well as worry about high risk of catastrophic failure like you do with timing belt driven water pumps on interference engines? (I realize that most consumers are ignorant to the point of not even knowing the risks and potential failure modes.)
Again - understood. The torque capability would have to be hugely overkilled to guarantee proper pump operation for a pump whose tightness was at the high end of the bell curve under all operating conditions. And there would be little safety factor for anomalous situations that tended to restrict the pump's rotation and/or flow characteristics.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.