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Update - Photos: I took some photos this morning in the daylight. I'm not sure if the liquid on the ground was from my MJ or something else. Hard to say. But it definitely looks to me like I'm getting some leakage around the base of the radiator. I've pasted them at the bottom of this post. I snapped these real quick on my way out to work. Will take a closer look after I get off. Some Background: If you have time, please read the whole post for all the details and then see my questions at the end. It took a while, but I finally got new tires on my MJ. I'd been driving on very old tires for way too long, and I was pretty sure they were causing the truck to shake at highway speeds. After getting the new tires installed (Good Year DuraTracs - 235/75/15), I was stoked to find that they significantly improved my drive on the freeway, and I drove about 30-40 miles at normal highway speeds for the first time in a long time. It felt great to be able to do that again, and I hope that I may finally be close to resolving my long battle with death wobble and not-so-deadly shimming. (If you've followed other posts of mine, you may remember that I had a lot of work done on the Jeep to fix the death wobble and that I'd made a lot of progress, but still needed to replace the tires). Anyway, that's not really what this post is about. The Overheating Issue: When I got off the freeway, I noticed that my heat gauge was redlining, so I pulled over. I popped the hood and saw that the coolant reservoir was boiling and that the cap on the reservoir is cracked. I let the truck cool off for a few hours and then drove back home (another 40 miles or so). It was probably around 80 degrees when I started driving earlier. By the time I drove home, it was night time and it was much cooler outside. I turned on the heat in the cab and made it all the way back home without any overheating issues or boiling (at least none that I could hear... I did not pop the hood when I got home, I just listened to see if I could hear any gurgling). My Theories So Far: The crack in the coolant reservoir cap concerns me, but I actually think that's been there for a long time. I have a 1987 2.5L, and my Haynes manual says that the overflow reservoir in these is not part of a pressurized system. But I'm no expert on this front. I have to do some more troubleshooting, but my first thought is that the water pump might be dying. The only other time I've encountered the boiling reservoir it was when my first water pump was shot. I replaced it probably 4 years ago now. Right before I noticed the overheating, I heard some engine noise that sounded similar to what it sounded like the last time the water pump went out. It was kinda like the sound of clanking metal being carried into the cab via tubes. It's not as pronounced as it was when I last changed the pump, but it definitely sounded similar. My Questions: Do you all think my water pump is going bad again? Do you think that's a good, low cost place to start? I drive the truck a fair amount, but it is not what I'd call a daily driver either. I have taken it on some pretty bumpy roads though since replacing the water pump and gone on some long road trips... so there's that. How vital is it to get a new reservoir cap for a 1987 2.5L? I definitely am planning to fix that ASAP, since it will be pretty cheap and I think relatively easy. Not trying to avoid it. Just wondering what my priorities should be. Is there any chance you think having the tires changed could have resulted in knocking something loose or shifting some fluid around or something? Like I said, this isn't exactly a daily driver, but I have made the trip I made today plenty of times over the past few years and sometimes on much hotter days. I wouldn't think the shop could have caused this, but I just am trying to understand why this happened today. I'm also wondering if driving it over 70 mph for the first time in a long time is why this cropped up today. Maybe the water pump has been going for a while and I just haven't pushed the truck hard enough in a while. Maybe the installation of power steering and new belts helped speed this problem along? When I got it worked on for Death Wobble, I also had power steering put in. And ever since then, there has been what I have assumed was belt noise. I tried a few simple things to resolve it, like tightening the belts, but I didn't ever get to the bottom of what was causing the noise. It wasn't a tell-tale screeching, but the noise would temporarily go away when I sprayed soapy water on the running belts, which made me think it was the belt. But maybe the soap was also lubing up the bearings in the water pump housing and thus stopping the noise temporarily? Finally, on a side note and in relation to the Death Wobble: How much jiggle is normal on a healthy MJ when driving on the freeway? I drove my truck for way too long with it's wobble issues before all the fixes (which I outlined in this comment). Now I'm a bit traumatized and I can't really remember what it was like before the wobble started presenting itself. I'm hoping that I start to get my trust back with time. Driving the truck today, after getting the new tires on, it felt soooo much better, but it still shakes when I hit a bump. I mean, obviously a 38 year old truck is going to shake when it hits a bump in the road, but I'm left wondering what is normal and what isn't... --- --- --- OK. I hope some of you will read this and respond to my questions. As always, any and all insights are appreciated, so thanks in advance!

Hey all, Here is the model and information you need to know about my Jeep. 1989 Jeep Comanche Eliminator, 4.0L Straight 6, Automatic Transmission, 2x4, I have A/C and cruise control. I have managed to complete my closed to open cooling system conversion. I did not spend a lot of money and I also did not go the cheapest route. I shouldnt have to replace any more water pumps or worry about cooling ever again. Here is a list of components that I bought: //////////////////////////////////////////////////////////////////////////////////////////////////// 2-Row Radiator - $100 https://www.amazon.com/gp/product/B01EVWTXLY/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1 Quality: 8/10 Functionality: 10/10 Comes with elbow and straight radiator cooling line fittings. Radiator Cap - $35 https://www.amazon.com/gp/product/B01F93S3E2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 Quality: 9/10 Functionality: 7/10 It is very hard to turn on and off the radiator. 4' of 5/8" Black Heater Hose - ~$15 total Autoparts store 4' of 3/4" Black Heater Hose - ~$15 total Autoparts store (2) 5/8" to 3/4" Hose Adapters - ~$15 total Autoparts store One Gallon of Concentrate Coolant - $15 Autoparts store One Gallon of Distilled Water - $3 High Flow Thermostat Housing - $33 http://www.hesco.us/products/7882/cooling-system/133247/hi-flow-thermostat-housing-hfth2#.WRuBvWjyuwU High Flow 180deg Thermostat - $19 http://www.hesco.us/products/7969/thermostats-and-housings/43013/hp--gmfordamcjeep-thermostat-180-degree-4364#.WRuIYGjyuwU Thermostat Housing Spacer - $37 http://www.hesco.us/products/7969/thermostats-and-housings/43017/thermostat-housing-spacer-hesths#.WRuIiWjyuwU High Temp Blue Silicone Gasket Maker - $12 Autoparts Store Hi-Flow Water Pump w/ Gasket - $87 https://www.4wd.com/p/flowkooler-high-flow-water-pump-natural-1747/_/R-GNLS-1747 Hose Clamps - ~$10 Autoparts Store 6' of 5/16" Hose for Radiator Vent - ~$10 Autoparts Store (1) 5/16-18 by ~2" long (1) 5/16-18 by ~1-1/4" long *Not exactly sure on length because I gave up on using the housing spacer (I will explain later) *The housing spacer and thermostat housing comes with gaskets. Total: ~$396 Well worth it, will never have a cooling issue. Works like a charm. My Jeep is preventing global warming from happening. //////////////////////////////////////////////////////////////////////////////////////////////////// A few pictures of stuff I bought... Start taking off parts... I had to take off the supports on top of the radiator, loosen the belt, and accessory fan. See photo below. NOTE: See the square rubber supports on top of the radiator? You need to reuse those. Take them off and put them on the new radiator so you do not forget... :doh: At this point I drained the coolant and took off all the hoses and transmission cooling lines. There is no pressure in the transmission lines so no fluid should leak out! Here is my old radiator taken out of the truck. This also shows the fitting types for the transmission lines. See the bottom elbow transmission fitting? My new radiator came with a replacement. The stock one is one piece and not a swivel fitting like the new fittings. You MAY have to grind, file, sand, etc. the diameter of the new elbow fitting so the plastic quick disconnect fitting will slide on the new fitting. Either that or you can file the plastic piece like I did. See below. ^^ That plastic piece goes on the elbow fitting ^^ I found that there was two holes that did not line up to support the radiator...Both sides. So I zip tied them on. Not too important since there are other brackets supporting the radiator on the top. First issue I found with the housing spacer... The belt comes pretty close the to lower housing bolt. See below. Also you can see two brass inserts. That is a 1/4" plug on the right (wrapped in teflon tape) and 3/16" plug on the left. Normally sensors go there on the newer jeeps. The Renix older jeeps have the sensors elsewhere. Second issue because of stupidity (Halfway my fault). Hardware store worker said the housing bolts were M8-1.25. They are not... They are 5/16-18. So I stripped out the holes and the bolts. I said screw the spacer and used original bolts. Bad luck for trusting the hardware store kid. :fs1: A little fabrication was needed for the radiator cap on the support bracket. It comes pretty close. Also, the vent hose is a 5/16" hose. I re-purposed my coolant reservoir bottle for my overflow tank. I forgot to take a picture but the two heater hoses go straight into the heater core. This shouldn't affect the A/C as the heater valve is open when the A/C turns on. This info is straight from the Jeep service manual I have. Heat comes out of the vents when the blower fan isnt on which is the only case which could be bad... Heat could build up without the blower fan on and melt/overheat things in the HVAC. Other helpful things to note: Make sure to put fan belt shroud/cover on before the new radiator is in. Make sure to put the rubber supports from the old radiator onto the new radiator. !!!!!!!! LET THE SILICONE CURE BEFORE FILLING THE SYSTEM WITH COOLANT !!!!!!!! Feel free to message me for any questions about my experience with this upgrade. :cheers: :rock on: :clapping: :waving: . :MJ 2: .

Hello there, I have an 87’ mj 2.5L, having a serious problem with overheating. For the first two weeks i had it it was constantly overheating, then in one afternoon i put a new rad in, new thermostat, new filters, and an oil change. Immediately it solved the overheating issue. Been about a month now of smooth and perfect temp running, until it sat for a week then started overheating again. Before it was the radiator overheating, now it seems to be smoking out of the back of the engine block. I’m thinking it has something to do with the thermostat, if anyone has any ideas or solutions or want more information, please let me know!!! Thanks

I'm thinking about replacing my radiator in my 88 4.0. Does paying more for a "high performance" radiator make the difference? Aluminum vs stock? I've been doing some research and came across the Mishimoto MMRAD but I'm not sure I feel like forking over $400. Does anyone have something they really like? Thanks.

DIY convert from closed to open cooling. This Write up is how I converted from closed to open cooling. You may choose other parts to achieve the same end result. I am converting because I am tired of messing with the pressure bottle, to remove the heater flow valve, and replace old hoses. Parts: Radiator with filler neck $82.57 * Part number: CU1193 Radiator cap $24.99 * (I bought a fancy cap with built in thermometer.) Part number: 2471S 2 Gallons antifreeze coolant $14.99 ea ($24.98 for 2) *** Item number: 7020022 10' 5/16 hose $19.90 *** $1.99 per foot Item number: 5194083 4' 3/4 heater hose $5.56 *** $1.39 per foot item number: 5192978 4' 5/8 heater hose $5.56 *** $1.39 per foot Item number: 5192951 Two 3/4 to 5/8 hose adaptors $2.99 ea ($5.98 for 2)*** Part number: 80424 A junkyard radiator bottle (I think mine was from a ZJ or WJ dad snagged it for me) Total conversion cost: $169.54 + S&H and tax Optional Parts: Later model thermostat housing with temperature switch new water pump Dual Fan Controller Second Electric fan for dual conversion Wire Relay or Fan Controller Power Switch MJ or XJ 2.5L Radiator Bottle $16.99 ** Part number: 52003213 MJ or XJ Bottle Cap $7.97 ** Part number: J3223202 Ordered from: Amazon.com * Morris4x4.com ** Advanced Auto Parts *** Tools: Gloves Safety glasses Knife or box cutter Phillips and flat head screwdrivers Bucket T-25 T-30 8mm Socket and or wrench 10mm Socket and or wrench Getting Started Start by draining out the old radiator fluid, removing the upper and lower radiator hoses, fan temperature switch, and if you have an auto transmission the transmission cooler lines from the radiator. Use an 8mm socket or wrench to remove the electric fan and clutch fan shroud. The radiator support is held on by several bolts 10mm and T-25 or T-30 (sorry mine where all stripped before I started not exactly sure the actual size). The bolts removed connect the support to the frame and front clip, then they are all out remove the radiator support. The radiator should come out without much fuss. With the radiator out of the way now would be the perfect time to convert to Dual electric fans and replace the water pump. Sadly I was running out of time due to fighting with stripped bolts so i was not able to do ether.... Depending on the radiator you get you may not need to change the thermostat housing. My thermostat housing is from a later model XJ, and can use a temperature switch. However the radiator I purchased has the hole for the fan temperature switch. Remove the 3/4 hose and the 5/8 hose from the thermostat housing and the water pump. Remove the old coolant pressure bottle and the hoses going to the heater core. Cutting the hose may be needed. The new hoses will need to be adapted from 3/4 to 5/8, the reason for this is the thermostat housing outlet is 3/4 connecting to the heater core that is 5/8, and the heater core outlet is 3/4 connecting to the water pump inlet that is 5/8. After all the old hoses are removed take your new 3/4 and 5/8 hose and route it however you like, then measure where to cut the hose in half. Use the 3/4 to 5/8 adapters as needed. Again the hose routing is: 3/4 from thermostat housing 3/4 to 5/8 adapter 5/8 to heater core inlet 3/4 from heater core outlet 3/4 to 5/8 adapter 5/8 to water pump The new coolant bottle is the next challenge. I ordered a 2.5L MJ/XJ coolant bottle that should fit on the drivers side fender, I will likely need to go back to a cone air filter to make room for it. Till I decide for sure what bottle I am sticking with I used one from a Junk yard Jeep and slightly modified it to work. I had to remove the old pressure bottle "shelf" to make room. I used a self tapping screw to attach the radiator bottle to the back of the engine bay where the old bottle was located. I routed the 5/16 hose around the back of the bottle and used the heater hoses as a bridge, ending where the radiator filler neck will be. Install the new radiator and reconnect the upper and lower radiator hoses. Reattach the radiator support. Connect the Coolant bottle hose to the filler neck. For good measure I zip tied all the new hoses in place. Fill the radiator system with 12 quarts (3 Gallons) of coolant. Must be a 50/50 mix, you can use pre-mix or concentrate with distilled water. you may not be able to fit all 12 quarts as there will likely be some coolant still in the engine. Bleed the air out of the system, Renix engines have a coolant temperature sensor on the back of the head accessible from the engine compartment. Clean up and all done Prior to this conversion My Jeep would boil over in 20 minuets and interstate travel was a no go. Now the temperature has yet to pass the 210 mark while traveling 75 mph on the interstate. A side note, my A/C seems to be blowing cooler as well now....

I have not converted to open cooling yet. I am planning on it though. The temp gauge gets up there in the red pretty quick. I know theres a little air in the lines but the top radiator hose is not moving fluid at all. is this the water pump? Also i think someone put stop leak in it cause the fluid in the reservoir looks like it has some grainy sawdust looking stuff in it. this stuff was foamy feeling. What is it though?!

So here is situation, I have just removed the 4 cylinder from my 86 MJ and replaced it with a sbc V8. After a multitude of problems from the drive train, bell housings, the clutch and a lot more i have finally progressed to turning the engine. However I discovered that the stock radiator will not support the the engine driven fan due to a clearance issue. It seems that the 4 bangers radiator was smaller and placed 4 inches aft than what the in line 6 was, so what i would like to try is find a MJ/XJ with the straight 6 radiator mounting brackets and try to install. Am i wasting of my time or does any one have any suggestions?

Hi, I have 1988 jeep comanche pioneer with a straight six and has a 5 speed manual. Currently I'm having over heating problems a lot of the lines for the radiator are cracked, brittle or broke right off. I'm wondering if anyone has some diagrams for the radiator and vacuum setup. Oh yeah, would really low oil cause the motor to over heat after starting up and driving a mile?

I just replaced my water pump on m y 1989 MJ 4.0L. During this project I noticed that the lower raditor hose going from the bottom of the radiator to the bottom of the pump has a spring inside to keep it form collasping. That spring is rusted to crap and peices are breaking off from it so I just bought a new hose. BUT I would like to put a new spring back inside. Can anyone tell me a place to but this spring or a pre-assembled hose with the spring already inside?

I don't know much of the seller or the product but while searching for a new radiator I found this one: http://www.ebay.com/itm/2-Row-BRAND-NEW-Aluminum-Radiator-Jeep-Cherokee-Comanche-2-5-4-0-/170857355687 its $65 shipped. I just purchased because I figured can't go wrong with a 2 row radiator for $65 with a lifetime warranty just curious if anybody has any experience/opinions with this product When I get to installing (delivery will be on or before 11/24), I will let everyone know how it went for anybody in the future looking for a replacement radiator as if it is a good radiator, its a damn good price too.

Hi! Been a while since I've been on the forums. I've been busy putting my rebuilt motor back in the MJ and putting some break-in miles on it. I have some questions about cooling though. What is considered a "normal" temp range?? 210-220? Lower? Higher? Here's why I'm asking... I had a local shop who sells remanufactured engines re build my 4.0 (long block). I finally got it back in and its been running a bit warm. I'll go drive it for a while (15-20miles) and when I sit and idle for a while, the temp would jump up to about 225-230 and the aux fan would come on. It would take a while to cool down back to about 210 then it would creep back up and just keep cycling like that until I started driving again. When driving at highway speed it would stay well above 210 unless it was raining...then it would drop well below 210. I've got a little less than 1000 miles on it at this point so I've been trying to fix the cooling issues. I started with the easy stuff, doing a chemical flush on the system. This seemed to help but it was still having issues. The coolant that originally came out looked like chocolate milk. I flushed it enough to get to a nice clear green when I drain it now. After doing that, I went to replace the thermostat. Only to find out that I hadn't installed one when I put the front of the motor together :doh: . I got a stock 195degree. That didn't help at all. It now warms up quicker...which is the job of the thermostat. But after it warms up, it doesn't start to cool down until the aux fan comes on. So I started reading forums..... Thats when I decided, it would probably be a good idea to get a new radiator since the original one had that chocolate milk running through it for so long and is probably corroded past the point of no return. And, I might as well get a new fan clutch, since the one I have is as old as the truck (92). So I bought an all aluminum 3 core radiator (and boy is it shiny! :brows: ) along with a brand new zj fan clutch. After an afternoon of squeezing and praying it would all fit, I filled it up and cranked it up. Seemed to work ok. At a cold start, temps get up quick, then I can see when the thermostat opens and the temp gauge drops about 10 degrees really quickly. I go for a drive, it gets to 210 and sticks there while I'm driving. If I stop though, the temp starts to slowly creep up. It takes a while, but eventually, the aux fan comes on to cool it down. When that happens it goes down quickly, then the fan goes off and it slowly creeps back up again. With the new radiator, it holds temp MUCH better while driving, and takes a while to heat up when idling and cools quickly once the fan comes on. Am I missing something? Or is this normal and I'm just being paranoid? Any advice would be helpful. --Additional Info 92 4.0 HO. stock, rebuilt recently. All new sensors including temp. Running "break-in" oil with zinc additive. (to be changed out soon for normal)