My timing belt broke on my 1990 maxima soon after I purchased it, used. I should have known to have it checked, but I didn't. I had it replaced, and it drove just fine. No bent valves or anything. Well, a week later the engine starting bucking, and I had to pump the gas to keep it from stalling. I replaced the spark plugs and spark plug wires, and tested the pressure. The right-hand cylinders were all low. I have no money, so I started taking the car apart to try to replace the valves myself. I get to the timing belt and - what is this? It appears that the guy put the belt on five teeth over from the marks. Would this be sufficient to bend my valves? Or at least cause significant damage to my engine?

 

The lines on the belt are used to line up with the sprockets while they are on their mark for installation. Once on correctly and the engine rotates, the lines on the belt will not line up again but the crankshaft/ camshafts should still line up on their marks when rotor is pointed to cylinder number 1. If you have everything apart, you can take the spark plugs out and rotate the engine manually via the large bolt inserted into the end of the crankshaft pulley. You should not feel any interference, if you cant turn it or you can hear things hitting, then suspect some damage.

Most importantly, notches on sprockets should line up with notches on rear the rear cover and notch on the bottom of the crankshaft about 5:00 on a raised lip, plus you want to be able to rotate engine without interference. Now if you dont take the plugs out you will feel the compression stroke but thats normal.

Good luck

 

Yeah, I have the rotor on No. 1, top dead center. The camshafts are off 5 teeth from their corresponding markings on the rear timing belt cover. The pressure on those three cylinders varied. It was 80 to 85 when I initially checked them, but then if I cranked the engine a bit longer, they would come out within acceptable limits. I'm guessing this is because not every cycle feels the effects of the messed up valves. Even if the valves are not bent, they might be coated in gunk, probably similar to the new spark plugs I got and just installed. I'll go on replacing the valves, but will also continue to look into the possibility that it was the incorrect alignment that set these bad things into motion. <-- pun, of sorts.

If I fix the valves and the car still rumbles, I guess I'll have to dig out the rifle and shoot the old girl.

 

Did you have the throttle open all the way as you were cranking?

 

Wow, let me know how it goes. How hard of a job is it to replace the valves, I thought the timing belt was time consuming enough. I'd leave mine alone unless I was sure they were broken or bent. Good luck!

 

I believe so. It was only the right hand cylinders that had low pressure. I don't see how the throttle would have allowed them to have low pressure, while the left side worked perfectly fine. And I do have some trouble turning the crankshaft. I am not sure whether to chalk that up to the weight of the components I'm turning, or the fact that the valves are bent. All I'm really interested in knowing is if putting the timing belt on with an incorrect alignment of the camshafts and the crankshaft sprockets would cause the valves to bend. I need to know for legal reasons, possibly. If I can prove that the mechanic that replaced the belt out there in the middle of nowhere did it incorrectly, and that his shoddy work ruined the valves on my car, then maybe I can receive some sort of compensation.

It's bad enough my SHO's tranny was ruined by the broken axle.

 

the reason i asked is because perhaps you had the throttle open while you were testing the left side and forgot to open it for the right side. I used a screw in type compression tester before, forgot to open the throtle, and got results around 80 psi, man it was a bad feeling, then i realized i had to open the throttle, pressure shot right up.
Turning the crank shouldn't be all too easy, valve springs and such have to be compressed.

I think you should do a wet compression test next, add a teaspoon of oil to each of the trouble cylinder, see if the pressure raises up. If it doesn't then most likely it's a valve problem (bent, broken, stuck, carboned up)If the pressure does raise, then perhaps the problem lies in your piston rings.

 

Very hard. I've never done anything this big on my car(s) before. Most of the time it was one or two tool jobs (good old pocket knife). But this valve thing is time-consuming and involving. I'm taking off so much of the engine that its slowly being rebuilt in the trunk. Might as well make it rear wheel drive now. I ordered the valves from some warehouse online thing. I have yet to receive them, but I got free shipping because my order was over $50. The Chilton's manual I am using also says I need to get the head machined. That will come later. I think I will take some pictures of it as I'm putting it back together. It's amazing how much I've learned about engines just by tearing mine apart.

I still like my SHO more, though.

 

Well, I called up Mossy Nissan Service in Houston. I asked them if the belt being five teeth off would make a difference. They affirmed it would, and probably could lead to bending of the valves. Unfortunately, they would not offer this verification as per my request to use it in legal matters. But I suppose I could just measure the distance between the valves and the piston heads when I open up to the cylinders, then determine the difference in clearance for each stroke. My evidence is coming together nicely. Thank you all for your help in this matter. Someone remind me to post some pics, or at least an account of my repairs, and I'll get to it in my spare time.

 

the belt being off five teeth would certainly cause problems with valve clearance, assuming that the valves opened immediately before/after the piston coming up.

my first guess would be that the belt jumped time because of poor tensioning, not that the belt was on incorrectly to begin with. something as simple as a misfire with a loose belt can cause it to jump time.
Since the car ran fine to begin with, THEN got funky, I would definitely suggest this being the case. Had the belt been off even one tooth after the install, the engine would be boggy and not run right. we had a belt replaced on my dad's '88 civic after it broke on a 500 mile roadtrip. luckily it didnt bend any valves.. When we picked it up, the thing was laggy and had almost zero power. you had to launch it at over 3500rpm just to keep from stalling the engine.
we drove it home and he had the local honda dealer tear it apart and re-time the engine. $300 later, everything was fine and the car ran smooth as silk again. (then he called the manager of shop #1 and had a few kind words, then was reimbursed for the shoddy work.)