Ricky9055

I have a 2000 jeep grand cherokee that has 132900 miles and just now got a knock in the motor in the top end ,but when i took the value cover off and checked my rockers they were okay.So i am guessing that you have run into this as i am now told this is very common on jeep between 1999 and 2005 can you tell me what it is and where do i start

IStoleIt

How did you check your rockers? You cant visually inspect for mis-shaping without removing them, you could just as likely have a bent pushrod tapping the roller beneath the rocker. Simply testing for loose rockers is only checking for busted springs. Speaking of rollers, you could have a bad roller, and the knock your hearing is it jumping the cam gear every rotation. The only good way to know, is to just buy the parts and tear it down. Maybe someone with a WJ will have extreme knowledge of a specific issue with the heads, and know exactly whats wrong, but so many moving parts, that are all metal-on-metal that could be the cause. Good luck

Ricky9055

I checked them by rocking them back and forth and there was no movement at all so i put the cover back on and am now here. I saw that youtube had what i had but ericthecarguy never told us what it was .

dave1123

4.7 or 4.0.

Ricky9055

4.0 straight 6 The sound of the knock is coming from the front of the value cover ,sounds like it is in the first couple of rockers ,but have had the cover off and all seams well.

Ricky9055

As i said before it is a 2000 Grand Cherokee Laredo inline 6 4.0L

Cherokee_Mike

This might sound crazy but check for play in the water pump pulley bearing.
Could be the impeller touching the head casting if the bearing is worn - clearance is very small.
Are you losing any coolant ?
Water pump bearing can fail over quite some time but coolant loss does not always become apparent until the bearing is almost done.

Ricky9055

Okay guys here is the full story of the maintains of my jeep .I bought it in june of 2016 and in august i changed the oil to synthetic oil ,when i did i could here a small tick and when i say small i do mean small and i figured it to be a lifter so i just let it go as you could not here it at all when you drove the jeep.I then had a problem with keeping the belt on and after months of this starting in September of 2017 i found the problem in February of this year and it was the bracket that held the alternator it had only one bolt left that was connect to the motor so i replace the lost bolts with new ones and that was fixed accept for i could not find the right size belt so we got a belt and made it go on and it was a good tight one and all was good ,but we also had the power steering pump off at the time to make sure that it was not the pump that was making the belt come off.I did not bleed the pump as i did not know that we needed to. I still have not done this.I was a very short time that this knock came into being and i have not done this because as i said the knock showed up and i wass thinking that after i fixed the knock i would bleed the pump.This brings you up to date as to what i have done to the jeep since i bought it.

97grand4.0

So, sounds like you have a serp belt that is not aligned, and an engine "knock".
When does it knock? Startup only? All the time? High rpm, low?
You have to solve the serp belt alignment and sounds like you have not done that. I did read recently a fellow had his harmonic balancer bolt loose and it wasn't all the way back. But you need to fix that.
Hope this helps.

Ricky9055

The Belt is fine as i said i have fixed that problem and the Harmonic Balance is good as we checked all this before i posted what the motor is doing now.But Thank you for the reply.

Ricky9055

Had a a Mechanic tell me two days ago to change my oil to straight 40 weight oil and that would take care of the problem for now he seams to think it is one of my lifters.

dave1123

Jeep specs say 5W-30 is the designed weight oil to use, but I switched to 10W-30 because I'm a dinosaur and don't feel comfortable using such a light oil. Having said that, I think 40W is much too thick to cure a stuck lifter. I'd think some Seafoam or other detergent in the oil would be a better approach.

The major problem with the 4.0 is a lack of valve clearance adjustment. As the valve train parts wear, there is no way to add preload to the lifters except replace the parts. If it's just one, I would suspect a worn cam lobe or lifter bottom. Doing some research I've found you could have a set of custom pushrods made that are 1/16" longer which should cure the problem of ALL of them rattling. I was going to cut the bottom of new rocker pivots by .5mm (.020") but they are VERY hard and would require grinding or EDM machining to do that. My 4.0 has 235K miles on it and cold idle sounds like pebbles in a tin can, but is quiet when it warms up. Go figure. She still has 55 psi oil pressure cold and 40 hot at idle.

Ricky9055

Yes i understand that the specs call for 5 w30 and i replaced it with some syc and then added sea foam and then changed it back to reg oil 10w 40 ,but as i said a mec told me to change it again to straight 40 to see if the knock goes away if not then he thinks it is the piston in the number 5 or 6 cylinder.The funny thing is the motor has lost no power at all.

Heapyjeepy

Before you go buying parts blindly I would locate the source of the knocking sound exactly. you can do this with a long screwdriver pressed up against your ear and various parts of the engine. wherever the sound is loudest will give you the best idea of the cause. I once thought I had bad engine knocking sounds but was able to track it down to loose torque converter bolts with the method I mentioned above. Hope this helps.

Ricky9055

Thank you for the advice now to find a 2 foot screw driver lol