lucky14
NAXJA Forum User
- Location
- Pittsburgh, PA
Hey everyone,
Experienced Jeeper here and new to this forum. Added an XJ to my family recently. I have a 97 turbocharged TJ on 4 1/2 in of lift, 33's plenty of mods, 08 XK on 31s some light mods. I am a professional automotive technician and have plenty of wrench time under my belt (just to give you a back ground and perspective from where I am coming from.)
But to the meat of the post…. the new addition is a 1998 XJ Sport, 4.0 with AW4 Np242, on 7" of lift, 35" MT Baja MTZ’s tires with a D44 swap, HP D30 and plenty of other mods. Due to a "blown engine" with 189K. The previous owner put rod and main bearings in it and still had the "knock". With that being said he was convinced that the engine was toast… so I got it on a steal.
I decided to make a new post after much searching. I made this decision due in part to some of the weirdness pertaining to the knock. I would love some XJ experienced knock guys/gals to lend a hand.
I've been around enough to have had a number of 4.0 and 258 engines and know how tough they are. I also know of the CHRONIC FP bolt problem. It had a bad knock from the front and bellhousing area. So I picked it up on the cheap. The knock was present on start up and the knock was consistent.
So here is the run down. I got the XJ in my shop today after work. Changed the water pump.. it was toast and knocking around, threw a new fan clutch on too. The knocking was diminished. After replacing the W.pump only a knock from the rear engine was present.
I did a cylinder balance test. The knock did not diminish or change when "killing" a cylinder. So it’s a pretty safe assumption that the noise is not a wrist pin, bent rod, piston slap/skirt noise. If it was the suspect/problem cylinder the noise would change pitch.
Oil Pressure always remains good at idle 40 psi+ unless it been idling for over an extended period of time and hots then its 35-30 psi (still within normal range).
So I checked the FP bolts with the help of another tech. I got about 1/8 and maybe 1/4 of a turn on two of the 6 bolts. The other 4 were tight. The noise was still present.
So we spun it over after marking the FP for a starting point. On one or two of the bolts after cleaning with brake clean, it looked like hair line cracks radiating from the Torque converter bolts. However, to my dismay there weren't any obvious cracks from the crankshaft bolts on the FP.
So I put leak tracing powder on the FP. (Think of baby powder in a can used to trace fluid leaks). It comes out fluid like and dries in a powder form.
After changing the oil refilled with 10w-40 and BG MOA additive. I let it idle for an about 20 minutes. During this time I used a stethoscope to poke around and listen.
The knocking was not coming from the block near the cylinders (although it resonated within the block). The sounds weren’t coming from any accessories as I started it without a belt on it when I was doing the water pump.
The damper is not wobbling and the noise wasn't evident in the timing chain area. The noise got louder the further back you traveled along the oil pan.
The noise resonated within the oil pan, but was NOT coming from within the oil pan.
The noise sounded louder when the probe was removed from the scope the tubing placed within the bell housing as it was running. When probing the transmission bell with the probe on the stethoscope it was loudest on the Transmission bellhousing and case versus anywhere on the engine.
The loudest spot was on the driver's side upper left of the bell near the CKS (crank sensor) it this area the knock was loudest and also accompanied by a ticking sound. The ticking accompining the knock is only hear with the stethoscope.
I shut the engine off and re-inspected the FP with the powder. (Think magnafluxing of a head) The powered should be blown off and leave the cracks more visible. I didn't see anything other than what little I had noticed before.
I have put about 30 miles on the XJ. The noise is rather constant and varies with speed. The noise doesn't change with engine load or if it’s in neutral or reverse.
I have also checked the CKS sensor, the torque of the bell housing bolts to block. I also checked to see if there was any slop in the FP as I rotated the engine with the FP as compared to the crank damper. All appears ok. The damper moves as soon as the flexplate is turned by the teeth.
I am confident the noise is within the bell housing. However, I know I need to drop the transmission to inspect the back of the block, check the FP, and the front pump/torque converter itself. I am a little dispointed that there really isn’t anything pointing toward “hey that’s it”.
Has anyone else had a similar experience with this knock with the absence of cracks or engine problems?
I am confident that it is the bell/trans area. But I certainly don’t have that “ah-ha” moment where there is some concrete evidence of what is wrong. Has anyone been surprised to find a large fracture when dropping the trans after everything looked “OK”?
I was expecting some flange separation, large cracks or something oblivious with as bad as the knock is.
I suppose it could be a torque converter or front pump. Just looking for some experiences for anyone else who couldn’t see any cracks or have any separation or slop in the FP. Thanks!
Experienced Jeeper here and new to this forum. Added an XJ to my family recently. I have a 97 turbocharged TJ on 4 1/2 in of lift, 33's plenty of mods, 08 XK on 31s some light mods. I am a professional automotive technician and have plenty of wrench time under my belt (just to give you a back ground and perspective from where I am coming from.)
But to the meat of the post…. the new addition is a 1998 XJ Sport, 4.0 with AW4 Np242, on 7" of lift, 35" MT Baja MTZ’s tires with a D44 swap, HP D30 and plenty of other mods. Due to a "blown engine" with 189K. The previous owner put rod and main bearings in it and still had the "knock". With that being said he was convinced that the engine was toast… so I got it on a steal.
I decided to make a new post after much searching. I made this decision due in part to some of the weirdness pertaining to the knock. I would love some XJ experienced knock guys/gals to lend a hand.
I've been around enough to have had a number of 4.0 and 258 engines and know how tough they are. I also know of the CHRONIC FP bolt problem. It had a bad knock from the front and bellhousing area. So I picked it up on the cheap. The knock was present on start up and the knock was consistent.
So here is the run down. I got the XJ in my shop today after work. Changed the water pump.. it was toast and knocking around, threw a new fan clutch on too. The knocking was diminished. After replacing the W.pump only a knock from the rear engine was present.
I did a cylinder balance test. The knock did not diminish or change when "killing" a cylinder. So it’s a pretty safe assumption that the noise is not a wrist pin, bent rod, piston slap/skirt noise. If it was the suspect/problem cylinder the noise would change pitch.
Oil Pressure always remains good at idle 40 psi+ unless it been idling for over an extended period of time and hots then its 35-30 psi (still within normal range).
So I checked the FP bolts with the help of another tech. I got about 1/8 and maybe 1/4 of a turn on two of the 6 bolts. The other 4 were tight. The noise was still present.
So we spun it over after marking the FP for a starting point. On one or two of the bolts after cleaning with brake clean, it looked like hair line cracks radiating from the Torque converter bolts. However, to my dismay there weren't any obvious cracks from the crankshaft bolts on the FP.
So I put leak tracing powder on the FP. (Think of baby powder in a can used to trace fluid leaks). It comes out fluid like and dries in a powder form.
After changing the oil refilled with 10w-40 and BG MOA additive. I let it idle for an about 20 minutes. During this time I used a stethoscope to poke around and listen.
The knocking was not coming from the block near the cylinders (although it resonated within the block). The sounds weren’t coming from any accessories as I started it without a belt on it when I was doing the water pump.
The damper is not wobbling and the noise wasn't evident in the timing chain area. The noise got louder the further back you traveled along the oil pan.
The noise resonated within the oil pan, but was NOT coming from within the oil pan.
The noise sounded louder when the probe was removed from the scope the tubing placed within the bell housing as it was running. When probing the transmission bell with the probe on the stethoscope it was loudest on the Transmission bellhousing and case versus anywhere on the engine.
The loudest spot was on the driver's side upper left of the bell near the CKS (crank sensor) it this area the knock was loudest and also accompanied by a ticking sound. The ticking accompining the knock is only hear with the stethoscope.
I shut the engine off and re-inspected the FP with the powder. (Think magnafluxing of a head) The powered should be blown off and leave the cracks more visible. I didn't see anything other than what little I had noticed before.
I have put about 30 miles on the XJ. The noise is rather constant and varies with speed. The noise doesn't change with engine load or if it’s in neutral or reverse.
I have also checked the CKS sensor, the torque of the bell housing bolts to block. I also checked to see if there was any slop in the FP as I rotated the engine with the FP as compared to the crank damper. All appears ok. The damper moves as soon as the flexplate is turned by the teeth.
I am confident the noise is within the bell housing. However, I know I need to drop the transmission to inspect the back of the block, check the FP, and the front pump/torque converter itself. I am a little dispointed that there really isn’t anything pointing toward “hey that’s it”.
Has anyone else had a similar experience with this knock with the absence of cracks or engine problems?
I am confident that it is the bell/trans area. But I certainly don’t have that “ah-ha” moment where there is some concrete evidence of what is wrong. Has anyone been surprised to find a large fracture when dropping the trans after everything looked “OK”?
I was expecting some flange separation, large cracks or something oblivious with as bad as the knock is.
I suppose it could be a torque converter or front pump. Just looking for some experiences for anyone else who couldn’t see any cracks or have any separation or slop in the FP. Thanks!
