Green Mesa XJ

Hum, then they set the timing to something close but as you tune it you may have to move the distributor but you’ve got no timing marks to check it with. Guess leave it alone unless you have to touch it. That noise I’m hoping somebody will chime in on it. To me it sounds like there is something lose in the top end: rockers, push rods, lifters, something like that. I’d pull the valve covers to double check if you haven’t already. Setting the valve lash is a PITA on this motor. Not rocket surgery just repetitive process to get it set. This thread has some good instructions, a few good videos if you search for them https://www.thirdgen.org/forums/v6/165647-valve-adjustment-2-8l.html Anyway that my guess for the sound if it’s not and it’s not oil flow related then it’s pretty much SOL start pulling the motor apart time. Sent from my iPhone using Tapatalk Pro

With lots of duct tape patches and nicks from Swiss Army knives. Complete with Roseanne Barr stop leak. A must for any fan of vintage television. Sent from my iPhone using Tapatalk Pro

I’d did some reading on gettin a IR temperature on the engine most suggest upper radiator near the thermostat housing, black surfaces for more accurate readings. Sent from my iPhone using Tapatalk Pro

So MacGyver was the jeeps previous owner [emoji4] Sent from my iPhone using Tapatalk Pro

I’m not sure about that noise. To me it sounds like if top end valve train related. But I’ll let others more versed in these things make a more definitive diagnosis. About the timing, you said you didn’t touch the chain, which is fine no reason to is it was replaced. I’m curious who set the timing and how. That engine didn’t have a distributor originally somebody put it in there and set it. It maybe perfectly correct or it may be off. Since it runs it can’t be too far off. Sent from my iPhone using Tapatalk Pro

I don’t think it’s temperature related per say any more than it is when the viscosity changes and the carburetor drop the rpm. I’m not ever sure you’re overheating or running hot. The radiator seems in the right range, the IR scan on the top of the motor might or might not be the correct way to get a reading. Sent from my iPhone using Tapatalk Pro

Cap on the res just sits there. How did y’all set the timing? Looking at the 3.4 timing cover it’s just a sensor, no markings. Sent from my iPhone using Tapatalk Pro

I’ve never seen a gunked up clog of stop leak like that before, it’s like they dumped it all at once not letting it circulate. Some times tell tale remnants settle around the cap trying to seal the expansion line. Dunno what the PO was trying to seal but they were serious about it. Maybe the heater core went out? Sent from my iPhone using Tapatalk Pro

The thing about the bubbles is you could still be burping out air. Just as part of the normal process of having swapped the engine out. air gets trapped and can take time to get out, also pin hole leaks and lose clamps can cause it too. I’ve had cars with blow head gaskets, it’s not subtle when it happens, not a few bubbles it was belching up huge amount of air and the temp would fluctuate between too hot and normal as air pockets circulated past the temp sensor. That’s what a normal BHG does followed by white smoke like you are electing a new pope. Then there is seeping BHG where minuscule amounts of coolant escape to the combustion chamber, looking for signs of this can drive a body nuts because any little change might indicate it when tests don’t show it. Well except for oil test where you send it off for analysis. Overheating, if that is what is happening, can be a old radiator, bad water pump, something else in the plumbing keeping the circulation off. It can be the fuel mixture is too lean. The timing can be way off and the engine still runs. It might or might not drive for $#!&, it’s kind of one of those things you’ll feel driving it. Timing off can cause it to ping. And other noises depending how bad it is off. The 2.8 (in general ) is supposed to be set for 10 degrees before top dead center mark, I think mine says 17 degrees BTC on the sticker. The 3.4 didn’t uses distributors so whatever you are using now was added to the motor after the rebuild. If it was done correctly I wouldn’t give it a second thought cause it not going to change except with vacuum advance if that is what your jeep had. That motor shouldn’t have blown the head gaskets easily unless it was done wrong, or really and truly ran past 250-280. I don’t necessarily trust the rebuild was correctly done, but I wouldn’t jump to the BHG ship just yet The rpm dropping is probably normal for it reaching operating temp and opening the choke all the way. You should just have to bump it up a little to get 700 to 1000 rpm curb idle. Engine dropping rpm also drops oil pressure. Oil pressure should be around 10psi at idle and 50-60psi at 2000 rpm. My old 2.8 has great pressure at idle 20 to 30 psi, which is partly why I never swapped it out. It never failed outright. I know it was high milage engine when I bought it (probably not the original motor...maybe) and I put another 100,000 miles on it. That auto zone link ought to have the instructions to bump up rpm..,, yes it does http://www.autozone.com/repairguides/GM-S10-S15-Sonoma-Pick-Ups-1982-1993-Repair-Manual/IDLE-SPEED-AND-MIXTURE-ADJUSTMENTS/Carbureted-Engines/_/P-0996b43f8038eee0 All of this is crap you’d never normally have to do just swapping the motor. Not knowing the history of the old motor or parts you are using is kind of like starting from zero because any questionable setting might have to be rechecked even if it’s not normally done in diagnosis. BTW if the head gasket really is just seeping a retorque to spec of the head bolts might reseal it. Long shot but it can work. But like I said the head gaskets maybe fine, you’d see oil level increasing and eventually muddy oil, as well as air bubbles in reservoir tank, and white smoke when it really got serious letting coolant in to the combustion chamber. Does the reservoir work? It should increase with the engine reaching temp the decrees as the coolant cools. Sent from my iPhone using Tapatalk Pro

Looks like at some point stop leak was poured in to the system. Or the cat did it. Sent from my iPhone using Tapatalk Pro

I’ve been using the Walmart stocked led for the XJ, two different brands. I believe Sylvania is one of them, I use the led color matching the lenses color, in the XJ that is red led for brake light, amber turn and white reverse. All except the white led are very impressive far as improved visibility goes. The oem relay for the turn signal flasher went nuts about the difference, changed it to Novita EL12 Flasher and it’s worked fine so far. Sent from my iPhone using Tapatalk Pro

Almost forgot is the timing correct? Sent from my iPhone using Tapatalk Pro

Radiator is plenty big enough as long as it is clean enough to have proper circulation. If it’s clogged it would cause it to run hotter. I’m not sure what kind of upgrade would fit in the same spot, probably something for the 2.5 XJ/mj. You said it slowed down, how so? RPM? The carburetor may be out of adjustment for operating temp idle. I think it can be adjusted easily enough if that’s the case. The noise is bothersome, If I were to guess without actually seeing or hearing I’d wonder if the noise was a bent push rod or lifters clatter do to low oil pressure. Since it’s rebuilt might be a good idea to check the push roads are adjusted correctly or at least nothing looks amiss. If you do more testing oil pressure can tell you a lot along with compression testing. I’m thinking oil pressure in case the bearings took a dive. Why do you keep thinking the motor is overheating? Did something else happen? Something possibly wrong with the engine rebuild? Just wondering because since the beginning you were concerned about how hot it got. Generally speaking iron head and blocks are more forgiving than aluminum head engines as Long as the gaskets are properly installed. You can run 195-210 and be fine, although my 2.8 seems to run 180-190 (haven’t tried IR temp reader to verify, didn’t have those in the rickety past or else I would have. ) only time I ever had the temp spike was high altitude and really pushing it to climb, other time was when the water pump died. I would hate for you to have to tear that engine down to fix it. Sent from my iPhone using Tapatalk Pro

My first though was something is dropped off inside the motor. If you have the tool or phone accessory you could scope it to see what happening inside the cylinder. I’d probably just pull the head to see what’s going on. I’d be surprised if it were something like scaling on the cylinder wall, dropped valve and/or screwed up position would by my guess. BTW Guys I used to work with would soak a locked up engine with ATF over night to free it up. May be redneck but it worked a number of times. Sent from my iPhone using Tapatalk Pro

I’m not too sure on the renix jeeps (87-90 4.0 mj &xj) it looks to me like there might be some relays missing from that block but I could be wrong. Missing bolts you should be able to get from the hardware store. Maybe somebody here will remember the sizes needed. Or that parts XJ you have. Yeah, that’s the back of the transfer case, which might have the selector lever to shift it in to 4 wheel drive still connected, it’ll be on the drivers side of the transfer case. You can lower the transmission a little and separate the transfer case from transmission, might make it easier to remove. Or you can pull them together if you want. Sucks the PO lost the bolts, I hate taking on abandoned projects just because there is always something else waiting to surprise as you reassemble. Not that it isn’t worth it to get this MJ back in the road. If too much is missing I’d go the ax-15 route since you have all of that on another XJ. Sent from my iPhone using Tapatalk Pro

91 is different, electronic speedometer for one. Not sure about the other gauges, temperature and oil are similar to the old 84-90 setup. I don’t think they are routed through the ecm like the 96 up. I found a 89-90 full cluster to put in my 85 XJ, speedometer cable was different, other than that it’s plug and play depending what year you have and of course replacing the appropriate sensors. Sent from my iPhone using Tapatalk Pro

Confirmed, oil pressure, fuel level and temperature hold last reading before the ignition is off, tachometer and battery voltage go to 0. At the top right hand side of the fuse block in side on the firewall drivers side there’s a 7.5 fuse for the instrument cluster, it is right under neath the hazard relay. I’d test there to see if your getting power. Sent from my iPhone using Tapatalk Pro

Fuel gauge will stay at last reading for sure (spent a lot of time trouble shooting that gauge). Not sure about the others, I thought the tach, possibly voltage reset and the others stayed put. Might have time this weekend to work on the old jeep a little, if I do I’ll check how the gauges work. I agree, I don’t think the cluster is getting power, which would be the fuse box or maybe ignition. Our 90s HO XJ did a weird thing where once or twice it’ll run but none of the accessories turn on. Can’t recall if the gauges worked or not when it did this. Sent from my iPhone using Tapatalk Pro

My apologies I helped the topic to stray. IMO it is either a cluster problem, or a wiring problem for all the gauges. Unless some of them actually work right??? I’d put the temp gauge back and test it according to the book, the extreme for both tolerances are easy to test going though the cluster and wiring. Tach might not be a symptom just a faulty ignition coil. But if it’s not apart diagnosing the temp gauge it’s might be better in another thread. I may pull my cluster like this out of storage to look at it. Sent from my iPhone using Tapatalk Pro

http://www.digitalcorvettes.com/forums/#/topics/149655 Here try this thread for an explanation. Sent from my iPhone using Tapatalk Pro

Oh for the tach Test. I assumed it was looking for good old fashioned Tesla approved voltage (BTW Nikolai Tesla invented the first ignition coil) Basically you are looking for a signal from the ignition coil which cycles it up to create the spark. I’m going to stop here cause my explanation will be lacking and ignorant. Did any of the gauges seem to work? Sent from my iPhone using Tapatalk Pro

Printed circuit looks ok. What happens if you do the factory Test with it in the vehicle Sent from my iPhone using Tapatalk Pro

From the 1988 electrical troubleshooting guide. If you can't read some of them I can email a better picture. Sent from my iPhone using Tapatalk Pro

IMO the gauge works. Or had worked, dunno if testing it could do anything to it. Can you get a picture of the printed circuit at the back of the cluster? If that's bad there's no point in testing the rest of the gauges, there are no replacement part for it for over 20 years. Either another 1984 to early 87 cluster or a 1988-90 cluster in its place. Aftermarket gauges would have to be bolted on to the dash or creatively adhered to the old cluster. I'll post the trouble shooting for the rest of the gauges. Sent from my iPhone using Tapatalk Pro

Other thing on these old clusters is the tarnishing on the plugs. Some clean the contacts, used to recommend an eraser to removed the tarnish. Not sure if that's still recommended. In my experience the printed circuits on several clusters from the Deep South peeled away. Actually the original cluster suffered from a bad printed circuit too and that was bought in the high desert. But I've never had anyone I tell about this issue have it as well. From what I've seen your circuit looked ok from what I could see of it. Next is the power to the cluster from the fuse. Also grounds need to be ok. Then I guess the wires in the harness, could have been nibbled on, have a broken wire some place, or where they connect to the sensor has a bad wire. The Tachometer resting at 4k then moving up as you rev the engine sound like it's not getting power all the time or maybe a intermittent ground. Could just be a bad tach too or for the wrong engine, but I feel like I've missed some symptoms. Adding a full instrument cluster to a jeep with idiot lights is plug and play for the cluster, with of course changing the sensors to the appropriate ones on the engine. So it shouldn't matter if the cluster was intended for that jeep for it to work. But you're also coming after god knows how many owners and how many fixes. Sent from my iPhone using Tapatalk Pro