Gstang117

Replacing the timing chain on my 89 4.0 Renix and had some questions since I've never done this before.
1: What else should I replace since I've got the front of the engine off?
2: What the easiest way to go about this? (example: Removing the entire front piece including grill)
3: Is there anything I need to watch out for when removing the old timing chain and installing the new one besides making sure it is lined up correctly?

freegdr

have you ever replaced a timing chain in a engine b4?

Gstang117

Nope but there's a first time for everything
Talked to a couple of mechanics, but I'd like to get a few more opinions.

freegdr

got a manual yet? if not get one ive done many but not a 4.0 yet ive heard theres a guide for keeping chain taugt id research that most important thing is alignment of dots on gears b4 removing and getting them back exact on install...

Cherockee

This can be very time consuming and I would go as far to say its a bit difficult too.

Things to replace while you're there: Water pump, crank seal on timing cover, drive belt, thermostat (since coolant will be drained), and quite possibly the oil pan gasket (and if you're going that far then the real main seal). You should also closely inspect the harmonic balancer. Often the rubber insulator dry rots and the process of removing it may damage it.

And since I brought it up, if you are reusing the HB then use the proper puller to remove it. Also, you need to take great care in re-installing it. The existing crank bolt is too short to use it to pull the HB back on- you'll end up stripping the threads out of the crank. Either get the proper tool to re-install it, or it's possible to use a longer bolt to draw the HB on far enough to then use the orginal crank bolt to bring it home.

As for as doing the timing chain there are a few things to pay attention to. First, count the teeth on both gears. My aftermarket set had 48 teeth on the cam gear and 24 on the crank gear. If this is what you have then you will have 20 pins on the chain between the two marks (cam mark will be around the 2 o'clock position and the crank mark will be around the 5:30 position) See pic:

If you have fewer teeth on both gears then I believe you should have 15 pins between the two marks (with the marks in the same position).

The typical method for installing the gears and chain is to position the marks together at their closest point. A straight line should go through the center of the cam bolt, cam mark, crank mark, and finally the center of the crank bolt.

One more thing. There is (usually) a spring and ball bearing in the end of the cam bolt. This presses against the timing cover and keeps the cam in place. I replaced mine just for peace of mind (that and the ball bearing rolled across the floor and I couldn't find it).

Thats all I can think of right now.

Gstang117

Pulled the distributor cap off and checked for play by rotating the crankshaft. Didn't seem like any. Checked the spark plugs and the tips are white. Think I've got an intake manifold leak

Cherockee

WTF, you go from replacing the timing set to talking about an intake manifold leak? Are we suppose to be guessing what's wrong with your Jeep? I didn't know we were still in the diagnosing stage....

Yoshi1983

I know old thread but I feel sorry for whom ever the motor in the pics of the timing chain the damn thrust bearing you can see behind the crank gear that's supposed to go under your number 3 main cap not number 1 I am sure that there is alot of piston wear from the crank moving so damn much