Timing chain question

[terrawombat]

I think I probably already know the answer to this, but...

 

I went ahead and pulled the oil pan off today because I had really nice leak somewhere near the rear of the pan. Anyway, I noticed that I could see the timing chain when I was under the truck and looking towards the front of the vehicle. Out of curiosity, I stuck a screwdriver up there to check and see if there was any slack in the chain. What I found was that I could pick the chain up a good 1/2" or more and it would flop back down when I let go. Now - I don't have much experience with these particular engines, but I've done more timing belt jobs than I can count on the Mitsu 3.0L V6 and slack in the belt is BAD. So, it sounds like the chain tensioner on my engine is shot, but I'm reaching out on here for a second opinion :)

 

Thanks!

[terrawombat]

Doing a little investigation, it seems as though the 4.0L do NOT have a timing chain adjuster, but the 2.5L do? What makes the 4.0L so special that Jeep/AMC thought the timing chain wouldn't stretch over time?

[Eagle]

Doing a little investigation, it seems as though the 4.0L do NOT have a timing chain adjuster, but the 2.5L do? What makes the 4.0L so special that Jeep/AMC thought the timing chain wouldn't stretch over time?

You have it backwards. Apparently you haven't worked on many classic American engines, because I'm 65 years old and I had never encountered a timing chain tensioner until the 2.5L Jeep engine came along. And I siuspect the real reason Jeep used it was that they wanted to use the same timing chain and gears in the 2.5L as in the 4.0L, but the 2.5L has a slightly lower deck height. If the camshaft is proportionally lower in the block, there would be some initial slack in the chain that would beed to be taken up.

 

Plus, the factory chain is a roller type chain. They don't normally wear out. On my '88 XJ I changed the timing set at 150,000 miles or so because I figured it was time. I was wrong. I had assumed the cam gear had nylon teeth like the old AMC V8s. Nope. Both gears are steel. There was NO slop in the original chain. However, since I had the new set ready to go in I installed it ... but I would not hesitate to throw the old parts into a motor for a heap.

[terrawombat]

Doing a little investigation, it seems as though the 4.0L do NOT have a timing chain adjuster, but the 2.5L do? What makes the 4.0L so special that Jeep/AMC thought the timing chain wouldn't stretch over time?

You have it backwards. Apparently you haven't worked on many classic American engines, because I'm 65 years old and I had never encountered a timing chain tensioner until the 2.5L Jeep engine came along. And I siuspect the real reason Jeep used it was that they wanted to use the same timing chain and gears in the 2.5L as in the 4.0L, but the 2.5L has a slightly lower deck height. If the camshaft is proportionally lower in the block, there would be some initial slack in the chain that would beed to be taken up.

 

Plus, the factory chain is a roller type chain. They don't normally wear out. On my '88 XJ I changed the timing set at 150,000 miles or so because I figured it was time. I was wrong. I had assumed the cam gear had nylon teeth like the old AMC V8s. Nope. Both gears are steel. There was NO slop in the original chain. However, since I had the new set ready to go in I installed it ... but I would not hesitate to throw the old parts into a motor for a heap.

 

Haven't tore into an American engine since my high school auto shop class nearly a decade ago - I've dealt with mostly imports with timing belts and, of course, tensioners :)

 

In your second paragraph, you mentioned there was no slop in the chain - meaning slop between the links or no sagging in the chain when it was installed on the engine? Because I can tell you I've got A LOT of sag in the chain as it sits on the engine right now. My initial measurement of 1/2" of slack may have been a little conservative as I went back under the truck and it was closer to an inch! If I had my camera with me down at my shop, I'd snap a couple pictures to show you exactly how much slack we're talking - maybe I'll remember to bring it with me tomorrow.

[jtdesigns]

Yes do take pictures cause I'd like to see what your talking about.. I'ma going watch this thread closely...

[Tomahawked]

If you have any amount of slop like described, it would be an intelligent decision to go ahead and replace it. Especially since you already have the pan removed. A little common sense goes a long way.

[jtdesigns]

If you have any amount of slop like described, it would be an intelligent decision to go ahead and replace it. Especially since you already have the pan removed. A little common sense goes a long way.

 

 

:agree:

[Eagle]

If you can see the chain sagging away from the sprocket from below the crank sprocket, you DEFINITELY need a timing chain. But that's technically not where you measure. I can't find any reference to allowable deflection in the Mopar shop manuals, but Haynes has a paragraph on it. You have to remove the timing cover. The measurement is made midway between the two sprockets. Pull the chain all the way out, then push it all the way in. If the deflection exceeds 1/2" you need a new chain.

 

Personally, I wouldn't accept more than 1/4" of deflection, since I know these engines should go 200,000 miles with NO wear/stretch in the timing chain. If there's significant deflection, either something is wrong or somebody didn't change the oil very often.

[terrawombat]

Yes do take pictures cause I'd like to see what your talking about.. I'ma going watch this thread closely...

 

I will take some pictures after work today - sorry about that, forgot to bring down my camera. I should just leave it down at my shop (shop and home are 3/4 of a mile away) since I don't ever use it for anything other than taking car/truck pics :)

 

If you have any amount of slop like described, it would be an intelligent decision to go ahead and replace it. Especially since you already have the pan removed. A little common sense goes a long way.

 

I generally reserve the common sense portion of my brain for items like 'put the toilet seat back down after I pee,' 'pot handles go to the inside of the stove,' 'your car keys will be in the last place you left them,' 'when the dog sits by the door and cries, it probably needs to go out and poo.' I have since removed the last common sense entry from my memory bank and have now added, 'if there is a considerable amount of slop in my timing chain - replace it.' Thank you.

 

If you can see the chain sagging away from the sprocket from below the crank sprocket, you DEFINITELY need a timing chain. But that's technically not where you measure. I can't find any reference to allowable deflection in the Mopar shop manuals, but Haynes has a paragraph on it. You have to remove the timing cover. The measurement is made midway between the two sprockets. Pull the chain all the way out, then push it all the way in. If the deflection exceeds 1/2" you need a new chain.

 

Personally, I wouldn't accept more than 1/4" of deflection, since I know these engines should go 200,000 miles with NO wear/stretch in the timing chain. If there's significant deflection, either something is wrong or somebody didn't change the oil very often.

 

And I forgot to mention the nice buildup of sludge in the bottom of the oil pan - so somewhere down the life of this truck, one of the owners was very, very mean to it. I was doing oil change/filter/lube every 1,000 miles or so for a while. This was used primarily as a farm truck for short distance runs and a lot of heavy hauling so I wanted to always make sure it had fresh oil in it. It then started developing a problem where the fuel would find its way into the crankcase - at which point I was changing the oil every 100-250 miles - but that has since been fixed (I hope). Anyway, I'm going to run a leakdown test on the engine today. I realize these tests should be done on a warm engine, which I can't do with no oil pan/oil, but I'm going to perform it anyway to see kind of results I get. I have a funny feeling that a few of the cylinders have a considerable amount of leakage - when I was turning the engine over by hand, I could hear air blowing back down at my head from the cylinders above...

 

...Now, why the hell is my dog sitting by the door crying?

[terrawombat]

Shot a little movie to illustrate my timing chain slack. Also cranked the engine over - let me know what you think.

 

[Eagle]

You need a timing chain. Cloyes makes a good one for the AMC engines.

[terrawombat]

You need a timing chain. Cloyes makes a good one for the AMC engines.

 

I was looking at Cloyes sets on RockAuto.com ($45 + shipping) or S.A. sets at Advance Auto ($55 and local pickup). I'll most likely wind up getting the one at Advance Auto since I can take the old set with me and compare to make sure I get the right parts. My local store has the timing cover gasket kit in stock, but will need to special order the chain set for me.

 

However, before I go putting money into the timing chain, I want to verify that my piston rings aren't shot. I have a cylinder leakage tester, but it's from Harbor Freight and not only are the instructions that came with it wrong, but all of the things I've found on the internet for cylinder leakdown tests seem to contradict each other. I found this video on Youtube, which made me laugh because I went through the EXACT same thing this guy went through and asked the same questions to myself.

 

 

[mvusse]

Agree, definitively needs to be replaced.

[jtdesigns]

I bet you engine has gobs of blow by too... That's that hiss your hearing, is compressed air pushing through the rings.. You should just swap it, or rebuild it.. IMHO....

[terrawombat]

I bet you engine has gobs of blow by too... That's that hiss your hearing, is compressed air pushing through the rings.. You should just swap it, or rebuild it.. IMHO....

 

Interestingly enough, no, not really. Yes, it does have some blowby as its evident from the oil buildup on the air filter, but it's nothing compared to some of the 4.0L Jeeps I've seen in my lifetime and were still running around like nothing was wrong. I believe my buddy even rerouted his PVC hose from the airbox to an oil catch can and that truck still seemed to run fine even with its 250K+ mileage.

 

Anyway, an engine rebuild definitely wasn't in my budget, so if that's what it's going to need, then it'll definitely have to wait. I've got some other projects going on in conjunction with the MJ that are currently sucking up most of my time/money, so I'll most likely get the new timing chain kit, swap it in and call it a day. I'll keep my eye out for some older or wrecked Jeeps for a possible cheap 4.0 swap.

[jtdesigns]

Did you not do a leak down test on it?

[terrawombat]

Did you not do a leak down test on it?

 

I did, but like I said earlier, I'm using a Harbor Freight leakdown tester with incorrect instructions and those YouTube videos I posted of the kids with the same tester is where I'm at right now - basically saying WTF? I tested the first two cylinders before I gave up, but I did get the pistons at TDC (it's pretty obvious when they are with the oil pan off), started the pressure at 0psi and slowly ramped it up to about 90psi. The cylinder holds some pressure and you can hear a little bit leak by, but I really don't have any way to quantify it with a percentage loss.

 

Now, according to some websites, you're supposed to connect the pressure source (air compressor) up to the tester without the other side connected to the engine. You slowly bring up the regulator until the percentage loss gauge reads 0%. You then hook up the tester to the cylinder at TDC and take a reading off of the percentage loss gauge. Now, for the two cylinders I did that to, I came up with around 80% loss. So, 80% of the air I put into the cylinder is getting blown right by the rings? Would a cylinder with a leakage THAT high still give me a compression reading WELL within spec? I tend to think not. I also tend to think this harbor freight tool is a POS, but I knew that already ;)

 

I have a Mitsu 3.0L V6 SOHC engine sitting on a stand that I know was in good shape when it was removed from a wrecked car. I'm going to try the same leakdown procedure on that engine and see what kind of results my HF tester gives.

[jtdesigns]

First thing first... DSM sucks....... Not, no one way around it... Watch that crank, it loves to walk. Sorry i had to confess my love for those nightmares.

 

As for the leak down tester. Usually the only time I really use a leak down was to find head gasket problems. I also "thought" you need the piston near the top of the compression stroke, but not TDC. I have connected my compression tester to an air compressor at ~60-70 psi to see if I got any bubbles in the coolant system.. For leak down I made one with a air regulator and ball valve. It was connected like this.. male connector > ball valve > Pressure Reg > quick connect > compression tester hose > spark plug hole. Put 90 psi on the regulator, turned ball valve off and watched the regulator gauge.. All this on warm engines if possible.

 

What are all your compression numbers?

[64 Cheyenne]

First things first, What is DSM ? :hmm: Second, I thought the video was cool, I'd probably agree that there is a cyl leakage problem. I also bought one of those HF gauges ( haven't used it yet),didn't know they had "issues".Anyways,this is what I found http://www.ask.com/bar?q=how+to+use+a+l ... tester.htm IMHO Makes sense to me. BTW I'd definitely replace that timing chain.

[terrawombat]

First thing first... DSM sucks....... Not, no one way around it... Watch that crank, it loves to walk. Sorry i had to confess my love for those nightmares.

 

As for the leak down tester. Usually the only time I really use a leak down was to find head gasket problems. I also "thought" you need the piston near the top of the compression stroke, but not TDC. I have connected my compression tester to an air compressor at ~60-70 psi to see if I got any bubbles in the coolant system.. For leak down I made one with a air regulator and ball valve. It was connected like this.. male connector > ball valve > Pressure Reg > quick connect > compression tester hose > spark plug hole. Put 90 psi on the regulator, turned ball valve off and watched the regulator gauge.. All this on warm engines if possible.

 

What are all your compression numbers?

 

The engine I was referring to isn't the "DSM" engine you're thinking of with crank walk - that would be the 2.4L I4 from a particular generation (I can't remember which). This engine came out of a Dodge Stealth (also technically a DSM, but usually people think of Eclipse, Talon, Laser when they hear that acronym). The Mitsu 3.0L V6 SOHC is actually a very stout engine when properly maintained - I sold a Stealth with one of those engines in it that had over 235K on the clock and was still going. Last I heard, the new owner blew out the transmission and swapped in a manual and has been doing fine since.

 

For the leakdown tester, you need to have both valves closed, basically. I guess I should have clarified that when I was saying TDC, I was on the compression stroke. The other time the piston would be at TDC would be at the end of the exhaust stroke/beginning of the intake so the valves would be in limbo and you'd never get a seal for a leakage test. Your homemade tester is something I'd like to try, although it's more of a rough check that makes sure your piston either holds pressure for a while or it doesn't. I bought my tester in hopes that I could quantify the cylinder leakage with a percent loss - At this point, that was just wishful thinking.

 

Dry compression test results on a warm engine, throttle full open, no spark plugs in any cylinders, 15 cranks per test:

 

1 - 140 psi

2 - 145 psi

3 - 155 psi

4 - 160 psi

5 - 140 psi

6 - 160 psi

 

First things first, What is DSM ? :hmm: Second, I thought the video was cool, I'd probably agree that there is a cyl leakage problem. I also bought one of those HF gauges ( haven't used it yet),didn't know they had "issues".Anyways,this is what I found http://www.ask.com/bar?q=how+to+use+a+l ... tester.htm IMHO Makes sense to me. BTW I'd definitely replace that timing chain.

 

DSM - Diamond Star Motors - A joint venture between Chrysler and Mitsubishi in the early to mid 90's. They shared a lot of parts and cars with each other during this time (3000GT/Stealth, Eclipse/Talon/Laser etc). In the "tuning" world, if you refer to a DSM, you're almost always talking about an Eclipse/Talon/Laser.

 

I'm going to do some more tinkering with my HF gauge. The first problem right off the bat with it is that the operating instructions are just flat out wrong. They tell you to connect the close the regulator, connect the tester to a cylinder and then gradually open the regulator until the 'percent loss' gauge reads 0%. Basically, their instructions read such that you'll get a 0% loss on every cylinder you ever test. You're supposed to hook the tester up to your air compressor with it NOT attached to the engine and bring up the regulator until it hits 0% on the percent loss gauge. Once you have that set, you hook it up to the cylinder and you should be able to measure the percent loss of the cylinder.

 

That website you posted is one of the ones I used to get the correct instructions. I will also replace the timing chain once I can verify the health of this engine a bit better.

[jtdesigns]

I was just razzing you on the DSM, me being a Honda guy. :razz: My boy had a modified Talon TSI that would scare you. Fun car to drive, it had a weird slow release clutch that wouldnt allow you to just dump and lose traction, but it would kinda slowly release, hook-up, and you'd better hold on.

 

Yeah I think your ok on your compression numbers, but you do have more then a 10% loss from 140 to 160 psi. Did you put a table spoon of oil in the cylinders? Whats called a wet test? Especially in the #1, #2, and #5 cylinders. The oil will seal the rings for a few secs and let you know if air is passing through them. You should get a 10~20 psi increase if the rings are worn. 140 is getting on the low side.

 

As for my homemade tester I used it mostly for finding blown head gaskets and worn valve seals on Honda engines.

Its pretty much like the little write up that 64 Cheyenne linked to.

 

Yeah just replace that timing chain and ride it. It'll slowly lose oumph but by the time it losses all compression you should be in a better position to swap, rebuild. The 4O engines are incredible engines for longtivity.

[terrawombat]

I was just razzing you on the DSM, me being a Honda guy. :razz: My boy had a modified Talon TSI that would scare you. Fun car to drive, it had a weird slow release clutch that wouldnt allow you to just dump and lose traction, but it would kinda slowly release, hook-up, and you'd better hold on.

 

Yeah I think your ok on your compression numbers, but you do have more then a 10% loss from 140 to 160 psi. Did you put a table spoon of oil in the cylinders? Whats called a wet test? Especially in the #1, #2, and #5 cylinders. The oil will seal the rings for a few secs and let you know if air is passing through them. You should get a 10~20 psi increase if the rings are worn. 140 is getting on the low side.

 

As for my homemade tester I used it mostly for finding blown head gaskets and worn valve seals on Honda engines.

Its pretty much like the little write up that 64 Cheyenne linked to.

 

Yeah just replace that timing chain and ride it. It'll slowly lose oumph but by the time it losses all compression you should be in a better position to swap, rebuild. The 4O engines are incredible engines for longtivity.

 

I imagine that slow release clutch was also intended to save drivetrain components.

 

The compression test results are dry - I haven't done a wet test on the thing yet, but I will as soon as I replace my timing chain. I'm also going to be redoing a dry test when the new timing chain goes in just to see what, if any, difference there is considering how much slack there is in the chain on there currently. I was laughing to myself when I was moving the crankshaft in miniscule amounts and the camshaft had yet to turn since the slack in the chain hadn't been taken up yet.

 

That's the plan at this point - fix the chain and ride the thing until it dies. It's a shame that someone neglected the poor thing somewhere in its lifetime. The truck only has 106K miles on everything, but the inside of the engine would suggest it has 300K or more. Ideally, in the future, I'd like to purchase a wrecked 97+ XJ and swap body parts over as well as the engine. I also want to get rid of my Peugot 5-speed at some point, too. Another day...