PT 2.4L is a non-interference engine

[RussV2]

Please correct if I'm wrong, but I'm reasonably sure that the 2.4L PT (as most auto engines these days) is a non-interference engine.

This means if you break a cam belt, you will not blowup your engine. The valves will not hit the pistons at any point in during the cam timing.

The pistons are slightly dished and have valve pocket reliefs in the dome.

Of course if your timing belt breaks, you're walking. But, you're not going to blowup your engine.

[CREWZIN]

Yes, your correct in part of what you heard. The valves won't hit the piston tops but the valves can hit each other. The only way to tell is with a compression check. Of all the owners that have had the timing belt break while they were driving, only two that I know of have had internal damage.

[RussV2]

Valves hitting each other can't happen without something else very major happening. Without the belt, the valves won't be opening / closing anyway.

I know of one owner who went 190k miles before the timing belt let broke.

I'm an owner that sticks to the maintenance schedule outlined in the owner's manual. I'm very particular about maintaining all my vehicles.

The point is, that you're not going to blow up the engine simply because of the timing belt.

[CREWZIN]

Originally Posted by RussV2

The point is, that you're not going to blow up the engine simply because of the timing belt.

I agree you won't blow it up but everything I've ever read and mechanics on this and other forums have confirmed, that the valves can hit each other if the timing belt snaps.

PT Do-It-Your.net is a paid forum put together by expert mechanics to answer questions regarding the PT. Here's one of them....

I have a 2001 LE PT w/139, 544 miles. I was going about 40mph up a hill when the rpm's on the gauge dropped to zero. The oil and engine light came on. I applied pressure to the gas pedal and the car went no where. I checked the computer for faults and it indicated "no faults" so I'm pretty sure that the timing belt broke. What has to be removed to get to the timing belt? I know the PT has a non-interference engine, but do you think there could be any damage to the engine? - James, from Connecticut.

Replacing the timing belt is a challenging job, which involves removing numerous components to access the belt. The service manual outlines the procedure in 25 steps, plus 6 sub-procedures. You will need a service manual, skill and the necessary tools and equipment to DIY. (The recommended service change interval is 90k miles under schedule B.) The PT engine is a non-interference motor, but only to a degree. Although the pistons will not hit the valves, the valves from both camshafts can hit each other. Valves hitting each other are very bad.

One more thing. You say you know someone that went 190K before the timing belt broke, fine. I know someone o this forum that went 89K before his broke. Neither one proves a thing.

[MX-5]

I understand the point of view.
What Russ has not seen is that the cams will continue to spin until the spring tension equalizes.

Remember, I work on these motors every week. I just did another timing belt last Thursday.
Sometimes you get lucky, other times the valves are bent.

[Travis2k7]

Originally Posted by CREWZIN

One more thing. You say you know someone that went 190K before the timing belt broke, fine. I know someone o this forum that went 89K before his broke. Neither one proves a thing.

What's the low end of the scale? How early does anyone remember timing belt problems?

I'm asking because I just took care of my 60k maintenance at 49k shortly after I bought my PT, and am hoping I don't have to do much to the car other than visual inspections, oil changes and rotations until the 80-90k timing belt change... (I'm looking at 80k to be on the safe side assuming I have no issues before then)

[Knotsobright1]

My PT has 66,000 and its getting a belt change but mostly because of a bad water pump so not really the same.

[RussV2]

Oh, I see now. I was thinking of a SOHC. With the DOHC, each cam controls a pair of intake or exhaust valves per cylinder. The timing belt along with the cam index insures the synchronizing of the cam timing and thus keeps the valves from hitting.

Loose the belt (especially if you’re zinging it) and there is a possibility that the valves could hit.

My bad and a good brain tease.

[Ironstosh]

Originally Posted by Travis2k7

What's the low end of the scale? How early does anyone remember timing belt problems?

I'm asking because I just took care of my 60k maintenance at 49k shortly after I bought my PT, and am hoping I don't have to do much to the car other than visual inspections, oil changes and rotations until the 80-90k timing belt change... (I'm looking at 80k to be on the safe side assuming I have no issues before then)

I am currently replacing my timing belt with only 68,000 miles on my 2001 PT

[85_305]

Originally Posted by RussV2

Please correct if I'm wrong, but I'm reasonably sure that the 2.4L PT (as most auto engines these days) is a non-interference engine.

This means if you break a cam belt, you will not blowup your engine. The valves will not hit the pistons at any point in during the cam timing.

The pistons are slightly dished and have valve pocket reliefs in the dome.

Of course if your timing belt breaks, you're walking. But, you're not going to blowup your engine.

Nope.. not interference motors. But be warned, the other part of what you said is incorrect. MOST motors ARE interference motors nowadays.

Originally Posted by Travis2k7

What's the low end of the scale? How early does anyone remember timing belt problems?

I'm asking because I just took care of my 60k maintenance at 49k shortly after I bought my PT, and am hoping I don't have to do much to the car other than visual inspections, oil changes and rotations until the 80-90k timing belt change... (I'm looking at 80k to be on the safe side assuming I have no issues before then)

89k miles and mine went