Timing belt went out, how can I check the valves?

[bobgengeskahn]

Ok, for starters, I am no great mechanic, but here is the situation at the moment.

My girlfriends 2006 PT took a dump last night on the freeway where she was able to coast from the fast lane to the shoulder and get towed. Not being there myself, and given the 15 min I had to look at it in the dark I am not completely sure what went wrong. However she was able to get it to a mechanic today that is a friend of the family that offered to take a look at it. He is saying it is most likely the timing belt (as is what I have come to believe after spending most of the day reading about it). The PT has about 100k on it and she has never changed belts... anywhere . So after finding that out I am sold on it being the timing belt.

He (mechanic friend) is saying that he can do the work for $250 after parts and covering 2 of 4 hours of labor. (never met this guy, he must be really good ) However, beggers cant be choosers and I don't have the time to fight with it for 2-3 days.

He is hoping that the valves/pistons are ok and is just going to go in, replace the belt and get out. My question: is there a quick simple way to check for further damage to see if it is even worth it? (and I do have a borescope available to me, just never dealth with this kind of thing before) Thanks!

[TurboDucky]

The easiest way I know of, is to pull the valve cover, and rotate the cams. Look for valve stems that are "stuck".

He's probably a little light on the 4 hour estimate - Plus, you should be replacing the water pump while he's in there.

[CREWZIN]

Maybe others will jump in, but as far as I know, you need to replace the timing belt (do the water pump and upgrade your tensioner while your at it) and then you can check on the valves. The engine needs to be turning to do a compression check. Unless you were at high revs when the belt broke, it's a good chance yo didn't do any internal damage. It's a non-interference engine which means the valve can't hit the pistons when the belt breaks but opposing valves can hit each other when the engine goes free wheeling. Of all the owners on this forum who have gone too far and broke the belt only 1 or 2 have had internal damage.

OK, Turbo Ducky has come up with a different way and agree with Ducky on being short on the hours for replacing the belt.

[bobgengeskahn]

Thanks for the quick replies! I figured he was probably a little light on the 4 hours, since most of what I have seen here and elsewhere is in the 7-9 hour range for a mechanic depending on what else they're doing down there. I will definately try to talk her into the water pump and the tensioner at the very least.

Turbo Ducky: I've never played with DOHC before, so when I am rotating them, I am assuming the belt is off, is it safe to rotate them independently? Or is there a technique to it?

[TurboDucky]

As long as the crank is not on top dead center, you'll (he'll) be fine. 1/4 to 1/2 turn off should be good. The design of the 2.4 is that when pistons 1 and 4 are up top, 2 and 3 are on the bottom. Anything other than top dead will have all 4 away from the top.

And, you can rotate them independently.

-Gary-

[UptownSport]

You could pull both cams and do compression test, by that time you could almost
do the head, though!

Never done this, assume (with good valves) it'd be in the very high category!!!!!

[UptownSport]

But we're jumping to conclusions, at 100k it could be multiple items.

[TurboDucky]

Originally Posted by UptownSport

You could pull both cams and do compression test, by that time you could almost
do the head, though!

Never done this, assume (with good valves) it'd be in the very high category!!!!!

I've never done a test that way. But I had a 4.7 that spit out some rockers once. I could tell the cylinders were dead, but it actually ran ok.

I think it has to do with the intakes valves not opening to let air in to compress. You get a lower overall compression.

[tryingbe]

Waterpump and tensioner might be fine now, but they're not going to last another 100k for sure.

In the 2.4 DOHC, valves can hit valves (rarely), pistons can't hit valves. Engine is most likely fine.

[bobdole369]

Originally Posted by UptownSport

You could pull both cams and do compression test, by that time you could almost
do the head, though!

Never done this, assume (with good valves) it'd be in the very high category!!!!!

My mech used a compression test (by manually rotating the cams so each cylinder had its valves seated) - then adding compressed air and watching a gauge. A leakdown test. Once he determined that 2 cylinders had no compression he pulled the valve covers to verify.