Your six-year-old econobox is starting to show a bit of wear and tear, but everything mechanical still works fine. Until it doesn't. Specifically, the engine suddenly goes dead silent one fine day. Your mechanic says your timing belt failed, then he chuckles into his shirt pocket. Now he gets to charge you for the tow, the belt replacement and a valve job, because there's no compression on two cylinders. You're one of the unfortunates with an "interference engine" — an engine that can leave one or more valves still propped open far enough to contact a piston when the belt parts. Sadly, sales brochures don't list whether an engine might suffer catastrophic damage if the belt goes.

You probably could have avoided this particular bit of unpleasantness with timely maintenance. It's best to replace the timing belt according to your carmaker's recommended schedule. For the record, many engines — like those in more expensive models — still use timing chains, rather than belts, like they did back in the day before the popularity of overhead camshafts. Unlike belts, timing chains usually don't have a routine replacement interval.

The timing belt (or chain) is the sole component that keeps the camshaft (make that camshafts on a DOHC or V-type OHC engine) and crankshaft in sync. So replacing this cogged reinforced-rubber belt at regular intervals — generally every 60,000 miles unless the car manufacturer specifies longer — is a lot less expensive and aggravating than having it break first. For your car's maintenance schedule, consult the owner's manual, alldata.com, or the belt manufacturer's poster hanging on the wall at your favorite parts store.

Timing Belts at FCP Groton

Though you'll spend only a few minutes replacing the timing belt itself, it can take an hour or more to dig down through the spaghetti of hoses, wiring and covers found in a modern engine bay. We even had to disconnect and cap a pair of fuel lines when we did the job on this VW 2.0-liter Four.

Study the procedure before digging in, either in a service manual or on the Web. On most transverse four-cylinder engines, you'll have to remove the passenger-side motor mount in order to gain access to the timing belt. This means the entire powertrain needs to be supported in that area while you're working. And finally, getting to the lower portion of multipiece timing belt covers usually requires underbody access. A fender cover doesn't hurt either, to protect the paint from your belt buckle and dropped tools.

(1) Remove any shrouding in the wheel well so you can access the crankshaft snout and the lower timing belt pulley. (2a) Find the timing marks on the flywheel and cam, and set them both to TDC. (2b) The flywheel pulley TDC mark is accessible through a hole in the bellhousing. (2c) The camshaft TDC is easy to find — especially if you add white paint as we did.

We cannot stress this enough: Be careful! Make sure you know where the timing marks are on your engine, and that you have them set up properly with No. 1 cylinder at top dead center (TDC) on the compression stroke before attempting to replace the timing belt.

Why? 1) That interference engine thing again; and 2) Every camshaft and crankshaft on planet Earth is indexed to No. 1 TDC. If you try to remove and replace the timing belt with the engine in any other position, chances are good you'll throw things out of time. Then you'll get confused and have to pull off the valve cover as you try to determine when No. 1's valves are closed (which begins the compression stroke) in order to re-index the engine. Get your marks lined up right the first time.

After you remove the top section of the timing belt cover, you should see a timing mark on the camshaft sprocket — this mark usually lines up with the edge of the cylinder head or valve cover. For the crankshaft below, there probably will be a timing mark on the damper pulley that lines up with another mark on the lower cover. Or, the service manual may direct you to the transmission end of the engine to look through a hole in the bellhousing for a timing mark on the flywheel. The flywheel is bolted to the other (transmission) end of the crankshaft. On some vehicles, you may find these marks in all three places.

(3) Support the engine with some sort of skyhook if you need to remove the rightside motor mount. Some belts are installed with a mount in their center, making changing them problematic. (4) The motor mount can now be removed temporarily.

Of course, there are professional engine-support rigs available for purchase or rent. But as you can see in our photos, some lumber and an adjustable tiedown strap work just fine to support the powertrain while you remove that cumbersome motor mount. Once it's out of the way, though, you're almost home. Just remove the rest of the timing belt cover sections and turn your attention to the tensioner pulley mechanism.

This tensioner may be an automatic hydraulic type that you simply crank in one direction to remove the old timing belt. Or, you may have to loosen the tensioner pulley adjustment bolt to release the tension and the belt. Before proceeding, confirm which way the engine rotates during normal operation. (Pull the fuel pump relay or fuse first if you need to disconnect fuel lines the way we did. Don't ask how we found this out. We're still getting the gasoline smell out of our coveralls.) Knowing which way the engine turns is important for checking the new belt's alignment later; you don't want to be off by a tooth on one of the sprockets. The easiest way is to have a helper bump over the starter motor with the ignition key while you watch the engine. Of course, now you'll have to reset your timing marks by hand. Don't rotate the engine backward to the marks. Crank it around forward to maintain the correct tension and to keep the belt from jumping teeth.

TDC? Now you can carefully slide the old timing belt off its sprockets and pulleys, while trying to keep the camshaft and crankshaft from spinning. With all the timing marks lined up, route the new belt around the largest diameters first, leaving the smallest pulley or sprocket for last. It's tricky to slip the new, stiffer belt over that last one, but you'll get it after a couple of different wiggling, jiggling attempts. Now, make sure the timing marks are still lined up.

Warning: If you know you're working on an interference engine, do not rotate the camshaft or the crankshaft independently while the timing belt is off the engine. You could cause the pistons to hit the valves, or vice versa, and cause the same damage as if the timing belt had snapped with the engine running — bent valves!

If you're working with a manual tensioner pulley setup, now is when you perform the factory procedure to tighten the new belt. A hydraulic tensioner takes care of this for you. Once the tension's set, place a socket on the big nut holding the front pulley on and use it to turn the engine over — two complete crankshaft revolutions in the direction of normal rotation. Line up all the timing marks again. Everything still on the money? Then you've finished replacing the timing belt — but you have another hour's work to reinstall the cam belt covers, any shrouding, and all the wires, engine accessories and hoses you moved or removed.

(5) Release any belt tension by freeing up the belt tensioner pulley. (6) Slip the new belt into place without disturbing the cam or crank pulleys, or the engine will be out of time. Check by slowly rotating the crank two full turns with a socket on the crank snout.

50. RE: Replacing a Timing Belt: Saturday Mechanic
93 3000GT SL DOHC my sweet baby I need it to run again...with gas prices I can't afford the 84 suburban. I need to replace the timing belt can someone give me step by step how to do this? And what else has to be replaced? The timimg belt is not broke but there are belt fibers in the housing. I am on limited funds a shop is not the answer, and too many friends dont want to work on the MITZ. Please Help ME Trixy in AZ

49. RE: Replacing a Timing Belt: Saturday Mechanic
I need the procedure for replacing the timing belt and the procedure for the adjustment of the belts, including the location of the timing marks on a 2004 dodge stratus with a 4 cylinder dohc

48. RE: Replacing a Timing Belt: Saturday Mechanic
I need to know whitch way the timing mark are suppose to point on a 92 toytoa 4 cyl I need to replace the bely it striped off Thanks

47. RE: Replacing a Timing Belt: Saturday Mechanic
I need timing marks for a 1995 mercury mystique 2.0 dohc

46. RE: Replacing a Timing Belt: Saturday Mechanic
need timing marks for a ford 99 contour 2.0 4 cyl.

45. To Naveen :
Hello Naveen : How are you ? Your car had run 126000 miles. Timing belt is not changed yet, now you want konw what is the better time to change it ? If you drive car in rule ,no violent drive . You'd better to change your Timing Belt when it run 100,000 KM if your belt is HNBR material ,And if your belt material is neoprene ,You'd better change it when run 50,000 KM .This is safe mileage . But if you drive very slowly ,You can change it when your belt is broken obvious . My opinion just for your reference ,You's better to ask your car maintain engineer . Regards lenfestey MSN : alexagxh@hotmail.com

44. RE: Replacing a Timing Belt: Saturday Mechanic
I have nissan pathfinder 1994 SE v6 engine. It has 126000 miles. Timing belt has not changed yet. I found that we need to replace eery 105000 miles. But what is the Max miles will timing belt can be used. Kindly provide me information. Thanks Naveen

43. RE: Replacing a Timing Belt: Saturday Mechanic
where are the timing marks on a 1995 olds cutlass 3.6 liter engine?

42. RE: Replacing a Timing Belt: Saturday Mechanic
I own a 1996 Toyota Camry it appears the cam belt has snapped does this mean the valves have bent too ?

41. RE: Replacing a Timing Belt: Saturday Mechanic
how do you install a cambelt on a 1500 dohc mazda 1998 engine

40. RE: Replacing a Timing Belt: Saturday Mechanic
Website: NORD - National Org...
My timing bely popped on the freeway and since then i have turned the ignition a couple of times and i think that i shouldnt have because it would have turned the crankshaft. The day before i had symptons of my car needing about five minutes to restart after me parking it. Might my car be an interference engine failure? Could my valves have bent?

39. RE: Can you provide timing belt / chain instructions for 1998 Nissan Altima?
I've got a 1998 Nissan Altima, with 80,000 miles. Earlier this week the words "timing belt" suddenly flashed into my brain, without suggestion, while driving. Could the car be telling me something? To date, it's been a great car without a single service issue. Thanks for letting me know.

38. RE: Replacing a Timing Belt: where you get the timing belts ?
When your loved car need to change the Timing Belts ,the garage is most of people's first choice ,when don;t we do it self ? we can spent less of money buy a good quality belt from shop or ebay ,and change it . i am specializing Rubber Timing Belts ,and we have a big factory in China ,produce high quality but compititve price belts ,just like : 1 : TOYOTA CROWN 3.0L / ENGINE is 2JZ-GE ,year : 1991-2002 . This Timing belt is 143MY25 , our price is just $ 4.29/pcs ,guarantee up 60000 kilometres . 2 : TOYOTA CAMRY 2.0L ,ENGINE is 3S-GE ,Year :1986-1992 . This belt is 178MY25 ,We sale $ 5.34/pcs ,guarantee up 60000 kilometres . If you will going to a garage to change this two belts ,you can make a telephone first to ask the charge ,and you will find which is better . If you have intersted ,you can contact me at MSN : alexagxh@hotmail.com ,my name is lenfestey . Welcome you /

37. RE: Replacing a Timing Belt: Saturday Mechanic
How do you replace a timing belt on a 94 Nissan Pathfinder?

36. RE: Replacing a Timing Belt: Saturday Mechanic
My timing belt broke on my 1990 geo prism and my husband replaced it but he needs to know how to reset the new belt. Thank you, Doris

35. RE: Replacing a Timing Belt: Saturday Mechanic
How many miles on a 93 Buick Century to change timing belt?

34. RE: Replacing a Timing Belt: Saturday Mechanic
is this an interferance motor? the garage here in Florida wants $2000.00 to replace the timing belt. he said the engine needs to come out to replace the belt and that the water pump should be replased also. I think this is too much where would be a good garage here in Ocala Florida to go for this mechanical work . this is my mothers car in florida and i am here in new england. thank you Joe K

33. RE: Replacing a Timing Belt: Saturday Mechanic
where are the timing marks for a 1996 VW City Golf Chicco

32. RE: Replacing a Timing Belt: Saturday Mechanic
I have a 96 Isuzu Rodeo that I need to get the timing belt off and I can't figure out how to get the tensioner to loosen up.

31. RE: Replacing a Timing Belt: Saturday Mechanic
Can anyone send me details of how to replace the cam belt on a Mazda 6 2 ltr Diesel 04 reg, Mazdas want £900 to do the job.

30. RE: Replacing a Timing Belt: Saturday Mechanic
I'm a DIY type of guy. I'm not a mechanic but i'm pretty handy and mechnically inclined. I have a 2001 2.4l Hyundai Santa Fe and I would like to change the timing belt myself. How do I change the timing belt on my car and what tools do I need to have?

29. RE: Replacing a Timing Belt: Saturday Mechanic
HOW MUCH DOES IT COST TO REPLACE A TIMING BELT ON A 95 MAZDA 626

28. RE: Replacing a Timing Belt: Saturday Mechanic
I need to know how to change the timing belt on 1991 Honda Accord LX

27. RE: Replacing a Timing Belt: Saturday Mechanic
i need any information on changing a timing belt and water pump on my 1998 toyota levin

26. RE: Replacing a Timing Belt: Saturday Mechanic
Where is the timing belt inspection cover located on 2000 Mazda 626 four cylinder engine located? Thanks, Harry

25. RE: Replacing a Timing Belt: Saturday Mechanic
How do I release the tension on the tension pully of a 2000 Daewoo Nubria. It appears that I need some factory tool.

24. RE: Replacing a Timing Belt: Saturday Mechanic
I have a 1999 accord v6 3.0 300,000km ,1st time belt change at 160,000km along with water pump.Coolant leak on right side in vacinity of water pump.Will change tentioner and w/pump at this time.Is there any other precaution I need to know.I need illustration and instructions please.

23. RE: Replacing a Timing Belt: Saturday Mechanic
I have the same questions as #1 above. I have a 1998 Toyota Avalon with the equivalent of 70 K miles (112K KM). The manual says to change the timing belt at 150KM however the dealer said it should be done now because the car is 10 years old. Is this correct?

22. RE: Replacing a Timing Belt: Saturday Mechanic
I have a Toyota corolla 1993. The timing belt and water pump were replaced about a year and one-half ago.I have a lot of oil leaking from crankshaft seal and other gaskets. Should those seals have been replaced as part of the timing belt replacement?

21. RE: Replacing a Timing Belt: Saturday Mechanic
I replaced my 2002 Jetta timing belt ( 2.0 L ) and three months later it jumped a few teeth. A technician at Volkswagen fixed it said he couldn't figure out why. Now one month later the same thing.

20. RE: Replacing a Timing Belt: Saturday Mechanic
Need timeing marks and illistration for 1991 Honda civic DX w/1.5 displacement.

19. RE: Replacing a Timing Belt: Saturday Mechanic
when do i change my Timing belts,2003 patfind v6 ,72300 miles on it,buy it new

18. RE: Replacing a Timing Belt: Saturday Mechanic
I'm being told that when the belt shreaded on my 1.7diesel 16valve vauxhall combo van that the piston has come up hit the valves. They said it did not show any signs of damage (no missfire or smoke)at the time but 100 miles afteri got it back a valve, which was stressed in the initial failure broke and has caused severe engine damage. Have you ever heard of a stressed valve breaking later?

17. RE: Replacing a Timing Belt: Saturday Mechanic
Ichangey spark plugs,oil,and air filter then drove the car itran fine so i put the cover back on the engine i couldn't find one of the screws then i went to start the car as soon as i bumped the starter i realized the screw fell in the oil fill this striped the timing belt and threw off the timing i can't find the point on the engine my car is a 2000 dae woo lanos i can't find a book on it please help me

16. Do I need Replacing a Timing Belt: Saturday Mechanic
Hi, dear friend: I have a 1999 Lexus RX300, it runs GREAT. Do i need replace the timing belt now?

15. RE: Replacing a Timing Belt: Saturday Mechanic
I have changed my timing belt on Daewoo Leganza. Now I feel vibration in the engine. Although the engine starts fine but in ideling I feel a lot of vibration. Is it one tooth off?

14. RE: Replacing a Timing Belt: Saturday Mechanic
Could I get some info on how to replace timingbelt on a 2000 acura integra.

13. RE: Replacing a Timing Belt: Saturday Mechanic
2000 ford focus timing photo

12. RE: Replacing a Timing Belt: Saturday Mechanic
i replaced the head on my 1993 toyota tercel and the crankshaft moved while head was off. Now i need to know if i have to remove the lower timing belt cover to get it back in time or can i use the marks on the lower timing belt cover for t.d.c. ?? Also does the oil pump have to be timed or is it ok?

11. RE: Replacing a Timing Belt: Saturday Mechanic
I need timing marks for 93 toyota tercel

10. RE: Replacing a Timing Belt: Saturday Mechanic
Can you provide timing belt / chain instructions for 1998 Nissan Altima?

9. RE: Replacing a Timing Belt: Saturday Mechanic
Hi, My 99 audi a6 engine made strange noise while in idle. The diagnosis was that the tensioner damper failed causing the timing belt to slip.Reccomendation that it has to be replaced and 2 clinders. When the belt just slips can it cause damage to valves sas well.Can the cyclinders be reconditioned ?Pl advise.Thank You ! Samuel.

8. RE: Replacing a Timing Belt: Saturday Mechanic
we just had the timing belt replaced on our 02 Santa Fe, and no damage to engine. can this be possible? before, mechanic worked on suv, he said compression looked good. since, my husband and I are not mechanics, even though we got 2 opinions on this from mechanics, how do we know it really was the timing belt, or could it have been the alternator and they are not trustworthy. i hate to be suspicious, but sounds like a miracle they could fix it.

7. RE: Replacing a Timing Belt: Saturday Mechanic
Can you tell me what the belt tension is supposed to be on a 1.8 ltr mits eclipse 1990?? and how to do it?? Thanks Alot!!

6. RE: Replacing a Timing Belt: Saturday Mechanic
how long does it take to change the timing belt on a 2000 ford focus?

5. RE: Replacing a Timing Belt: Saturday Mechanic
I NEED THE TIMMING MARKS FOR PT CRUSIER

4. RE: Replacing a Timing Belt: Saturday Mechanic
Hi They change my timing belt,ac belt, powering steering belt altnator belt. I have this screeching when i turn very loud. Very loud. Went back and adjusted it was better but it was still there. Now It is louder and any slight turn it screeching help

3. RE: Replacing a Timing Belt: Saturday Mechanic
For heaven's sake, LISTEN to what you are being told here! My sad cambelt story is that I asked (and supplied) a new cambelt to be fitted to my diesel Audi 100 during fitting a new cyl. head gasket. The mechanic didn't bother to fit the new belt saying "the old one looks all right". The very next day...yes, you've guessed, it snapped, breaking the ohc. camshaft into 5 pieces, smashing the cap bearings, writing off the cyl. head. A new head would have cost over £2000. Result??? ECONOMIC WRITE-OFF. The car wasn't worth the cost. I've warned you, the mechanic here's warned you, so don't say you weren't warned. REPLACE THE BELT, ALL TENSIONERS, THE WATER PUMP, AND DO IT EXACTLY BY THE BOOK!!!!

2. RE: Replacing a Timing Belt: Saturday Mechanic
I had a timing belt replacement done last year. My car is now running very rough. A different garge is saying that it may not have been installed correctly. When they(the second garage) do a timing belt they replace pulleys and tension ?, and water pump as they all work together. It's the only way to guarantee their work. The first garage saying they don't replace parts unless they need to be replaced. The first garage is willing to take a look at the timing belt. But I'm afraid they will say it's been running for a year, and not their problem. Sue Billings

1. RE: Replacing a Timing Belt: Saturday Mechanic
My toyota dealer told me that timing belt on my 2001 Avalon, with only 37,000 miles may need a timing belt because of car age rather than mileage. Is this correct? thanks