Heavy Metal

I am in the process of replacing everything except the compressor and the evaporator in my MJ and I will be charging it with R-152a, better known as dust-off (difluoroethane). I will tell you how it goes. But, you can read through an SAE powerpoint presentation on it here.

Gonna need to re-gear that diff... :eek:

Hmm, I may return to a factory pressure cap. It seems unwise to run the system at nearly double the pressure it was designed for. Not that it is always in the low twenties during operation, but it gets pretty hot here (Hawaii) and the cooling system in my truck was pretty neglected when I got it.

When I get some free time I intend to remove the manifolds and replace the rubber plug with a real plug. I will be sure to check the block for cracks, and use a sealant. I have heard mixed things about sealants on the plugs, but it certainly can't hurt. Also, after the truck overheated I thought I had blown the head gasket. It looked like it was weeping fluid from the gasket down the block. Turns out my block is so grimy and oily it was just warm sludge running down the block :rotfl2:

Today the number four (from the front of the block) freeze plug blew out while I was driving on the highway. My idiot light failed to warn me of the impending disaster (just happened too fast or maybe requires liquid to trigger the thermocouple?), luckily I was able to get my jeep off at an exit just after steam started to make its way through the firewall. Not only was there a NAPA conveniently located across the street from where my truck finally decided to die, but they had a 2" rubber expansion plug in stock and I was able to get it installed from underneath the truck! My luck was unbelievable today. My question is why did this freeze plug let go like it did? I know that the previous owner had new plugs installed a little under one year ago. I suspect that it is the Gates 31329 coolant reservoir cap that I am running, it has a 20-24 PSI relief valve. Stock is what, 16 PSI? I think that some people here are running the 31329 cap without issues, but maybe this freeze plug was not properly seated, or it had a bad taper, and the additional pressure was just a bit too much for it to handle?

Anybody know what temp is required to trigger the overheating light? Edit: Just realized how old this thread is, sorry for raising the dead.

My oil filter adapter was leaking a small amount of oil, and it would collect on the rear or my oil pan near the drain plug and the bottom of the bell housing as well. There are three o-rings in the adapter.

yxmj, I believe you are correct and it is leaking from the o-ring coupler on the hydraulic line into the cylinder. I got under the truck and pulled gently on the bit of hard-line that runs into the bell housing and was able to get it to leak when the truck was not running. I noticed that the hard-line had been resting against the underside of the body, there was evidence of chafing on the undercoating, this must have transferred vibrations directly right to that old and tired o-ring and hastened its demise. Well, I guess I am going to track down a transmission jack to rent/borrow. I think I have a handle on all the steps to pull the transmission, I am worried about reaching the two transmission-to-motor bolts hidden way at the top of the bell housing. I can't see them right now and from what I have read, they may be external (male?) torx head bolts? Is this likely for the 4.0 and AX15? I have been reading that they are E-12 size, that sound about right? Hopefully the new motor mounts are flexible enough to let me lower the transmission a bit to expose them.

The internal slave cylinder on my 1990 MJ SporTruck (AX15?) 5 speed manual is leaking. After I got home from a ~70 mile trip I was checking my fluids and I noticed that the master reservoir was empty (it is surprising that I made it back with no issues actually). Immediately I checked for leaks from the master in the engine compartment, and inside the cab near the fuse box, there was no sign of leakage. Additionally the line from the master to the slave is fine, however there is evidence of leakage at the mouth of the bell housing. Interestingly, it only seems to leak when the truck is running, I confirmed this by filling the reservoir and letting the truck idle in neutral for a minute, and to my disappointment, watching a steady drip from the bell housing. I shut the truck off and the leak subsided. Here is what is most disturbing. The day before this trip, I replaced both of my engine mounts (4.0L L6), using a small floor jack to support the motor at the oil pan while I removed and replaced one mount at a time. I am skeptical of coincidences, so it seems to me that I may have damaged the internal slave somehow during the motor mount replacement. Does this seem plausible? My driver's side mount was split about halfway up from tension due to motor torque, and both were noticeably collapsed from bearing the motor's weight. Is it possible that by the new motor mounts changed the angle of the flywheel-to-clutch interface enough to bust my slave cylinder seal? Judging by the fact that it is only leaking while the truck is running I assume it is the seal that is damaged, otherwise it would probably leak when it was off as well right? Coincidence or not, I am going to bleed it a few times tomorrow in a desperate attempt to see if it sorts itself out so I don't have to drop the transmission!

I can get to them all if I use a 3/8" drive ratchet and a 10" extension with two knuckles (one at each end of the extension). This is with normal sockets, deep sockets get stuck in between the exhaust manifold pipes and the intake manifold in my experience. I have to straddle the driver side fender with one leg inside the engine bay (foot planted right about where the airbox goes) to reach the bolts. This allows me to use my left hand to reach up under the intake manifold and guide the socket to the bolt heads. It is a huge pain in the @$$ and if anyone has a better method I want to know!

My truck was lacking power when the throttle was about 2/3 or more. I found two fuel leaks, the first was fuel leaking into the vacuum side of the fuel pressure regulator (fuel in the vacuum line) and the other was due to a loose valve core in the schrader valve test port on the fuel rail. These two leaks were robbing pressure from the fuel system. I am sure that the leaking injector would cause similar symptoms, but you might want to check these areas too.

Damn, you guys are right, I must have gotten mixed up when I was under my truck and not realized that there was a second sensor hanging out above it. Yeah it is my knock sensor. Also, what do you think the urgency is for replacement? The truck seems to run ok, but it could still be working in some capacity. I can probe it, but I'm not sure what to look for. Also if the sensor is damaged I imagine the ECU defaults to some very conservative timing schedule to prevent damage?

I can take a picture of it tomorrow, but it is the exact sensor highlighted in yellow in this diagram: According to this page http://www.jeepforum.com/forum/f11/coolant-temp-sensor-where-1233064/ it should not have anything to do with my dash not having gauges since the sender is on the back of the head near the MAP sensor.

1990 SporTruck The casing around the coolant temperature sensor (mounted in the block next to the coolant drain plug) came apart in my hands the other day. The gelatinous material in the sensor (or maybe just an insulator?) is now exposed. I was browsing around the web looking for replacement sensors and I noticed that they all have 3 pin connectors, yet my particular sensor has an EV1 type connector (like my injectors). What is going on here? I don't have a temp gauge on my dash, just an idiot light, does this have anything to do with the type of connector?

1990 Comanche SporTruck Are there supposed to be Belleville spring type washers under the bolts on my valve cover, similar to the intake/exhaust manifold? Currently there aren't any. I just replaced my valve cover gasket and I noticed that all of the bolts were finger loose! I torqued them all to 55 inch pounds moving in a circular pattern similar to that reccomended for the head bolts. I hope that they were loosening because the PO forgot to go over them a few times, as bolts loosen during the torquing process, and not because I am missing spring washers.

Thanks!

I am trying to figure out what the specs are for the torx bolt used at the back rest pivot point on the bench seat of my 1990 Comanche. Are they a commercially available bolt or application specific? The bolt in question is #9 on this diagram.