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Mj Still Overheating!!!!


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I have a 1988 renix mj with a 4.0, 103K with the closed loop system that was from Canada. It started to over heat on my in the city a month or so ago in the peak of summer about a month ago. I live in south texas so temps get up to 100-110 all summer. I wanted to eliminate all possibilities so I started to replace the WHOLE cooling system.

 

One thing to mention. This truck did not come with ac from the factory and it did not come with the Electric fan from the factory also.

 

 

Items Freshly installed:

 

New zj Fan Clutch

New CFS 3 row radiator

new Flow Kooler water pump

New High flow thermostat

New themostat housing

New upper and lower radiator hoses

New Fan Shroud

New Serp Belt.

New sealed Overflow Tank

New coolant

 

I got it all hooked up and drove it for a bout 20 miles on the highway and a little in town and it did fine. Then I parked it and let it Idle. And this is what it did.

 

Outside Temperature : 75 degrees Fahrenheit

Time : 8:45 PM

 

don't have a picture of when I parked it but it was sitting at the normal mark.

 

 

Time : 9:05 pm

Time elapsed : 20 mins

 

Time: 9:15 pm

Time elapsed : 30 mins

 

Time : 9:25 pm

Time elapsed : 40 mins

 

Time : 9:35 pm

Time elapsed : 50 mins

 

Time : 9:45 pm

Time elapsed : 60 mins

 

I will say the temps do not climb nearly as fast as it did before I replaced everything but then again it was around 85-90 degrees when I did.

 

Let me also note that like I said the truck was made in Canada that's why the temperatures are in Celsius. However I know the truck has been in Texas for at leased the last 10 years.

 

Lastly, The Truck does not show any signs of head gasket failure. exhaust is VERY clean, no smoke, no water or coolant coming out of it, and it does not burn it.

 

 

Please help me and tell me what to do now!!!!!surrender.gifsurrender.gif

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Has it ever boiled over? Have you verified the accuracy of the temp gauge with a known good standard? Have you replaced the temp gauge sender? Do first things first. I can not believe people blindly start replacing their entire cooling system while relying on the the stock temp gauge.

 

But wait, there's more! I did the same exact thing as you (after verifying the dash gauge accuracy). Replaced the entire cooling system. Turned out after all the $$ spent and aggravation, I found out the the cat was nearly clogged shut while redoing the exhaust system. There's never an easy answer for cooling.

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No I have not check the temp gauge or sender, and I have never let it get hot enough to boil over before turning it off. The I have new exhaust, header back. What's the easiest way to test the sender and gauge?

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Pick up a new temp sender, and replace it. Cheap, easy. They go bad commonly, especially the aftermarket junk. But first after you remove it from the head, if you can, beg/borrow a mechanical temp gauge and screw it into the head bung (1/8" pipe thread) and verify it's temp indication vs. the dash electronic gauge.

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Fast & Dirty - - - Engine cold - Radiator full - Start truck & let run for 60-90 seconds - Turn off & remove radiator cap - have your ear close enough to the cap to be able to tell if the system was pressurized - - - - - - -Lazer temp readers are worth having - 25-35 bucks - Check radiator hose in & out, thermostat housing, front of head, back of head-all the obvious - brake rotors & drums & so on - Around the house for HVAC, chances of getting lucky at bedtime - all kinds of things - - - used mine a couple yrs back to ck fever temps when my 2yr old grandson was having problems & was way easier than a thermometer - just read under arm temp - neat tool.

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Couple things, are you sure it's "full" of coolant? A closed system sometimes requires "burping" to get it full. Jack the back end up and remove the temp sender until coolant comes out, then top it back up.

 

Also, is it possible that the lower rad hose is collapsing?

FWIW that last pic looks like its just over 230F?

My 0.2 cents, good luck!

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Time : 9:35 pm

Time elapsed : 50 mins

 

Time : 9:45 pm

Time elapsed : 60 mins

 

I will say the temps do not climb nearly as fast as it did before I replaced everything but then again it was around 85-90 degrees when I did.

 

Let me also note that like I said the truck was made in Canada that's why the temperatures are in Celsius. However I know the truck has been in Texas for at leased the last 10 years.

 

Lastly, The Truck does not show any signs of head gasket failure. exhaust is VERY clean, no smoke, no water or coolant coming out of it, and it does not burn it.

 

 

Please help me and tell me what to do now!!!!!surrender.gifsurrender.gif

 

Even in the last photo the needle isn't in the red -- what makes you think you were overheating? There's no way to convert those hash marks to a temperature -- the dial isn't calibrated linearly.

 

Was it boiling over? If not, it wasn't overheating.

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Couple things, are you sure it's "full" of coolant? A closed system sometimes requires "burping" to get it full. Jack the back end up and remove the temp sender until coolant comes out, then top it back up.

 

Also, is it possible that the lower rad hose is collapsing?

FWIW that last pic looks like its just over 230F?

My 0.2 cents, good luck!

 

Well the back sits about 4 inches higher than the front on level ground so I figured that was high enough to burp it.

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Even in the last photo the needle isn't in the red -- what makes you think you were overheating? There's no way to convert those hash marks to a temperature -- the dial isn't calibrated linearly.

 

Was it boiling over? If not, it wasn't overheating.

 

It was not boiling over, and the reason is I turned it off before it got there, I do not want to blow a head gasket by letting it overheat all the way, However if I did not turn it off it would have gotten into the red.

 

as fr as the gauges were concerned... if you drove the truck off the lot and temps were looking like that a mile down the road, there is no way the dealership would say " yup thats normal for it to rise untill it pegs out and over heats.......100 degrees C is 212 F therefore, 125 degreesC is equal to 257F. I would say my needle was 3/4ths the way to the 125 mark, so roughly thats 235-240ish F..... Thats not normal and is way to hot for having a completely new cooling system ans for it sitting at a idle on a COOL 75 degree day...

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UPDATE: I took the truck today to the scrap yard to drop off a lot of junk to get some cash to fix the truck. I took it to a shop and are having them do a pressure test and check the head. they are also goin to look at a bad leak that has developed around the slip yolk shaft. And one more thing. While getting out on the high way I floored it in 1st gear and it seemed to bog/hesitate, the it opened up and took off. any ideas? it only doest it in first when you floor it from a stop. BTW it is a automatic.

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UPDATE: I took the truck today to the scrap yard to drop off a lot of junk to get some cash to fix the truck. I took it to a shop and are having them do a pressure test and check the head. they are also goin to look at a bad leak that has developed around the slip yolk shaft. And one more thing. While getting out on the high way I floored it in 1st gear and it seemed to bog/hesitate, the it opened up and took off. any ideas? it only doest it in first when you floor it from a stop. BTW it is a automatic.

 

When my Suburban did that it was a mostly clogged catalytic converter.

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Just talked to the shop and they said they were able to duplicate the problem. Then the did a pressure test on the head gasket and they said they had no problems with that and the head gasket was good. Then the put a little 10 inch fan in place of were the factory electric fan was and said it never got over 205. The demmed the problem being from me mounting the tranny cooler in front of the radiator on the side that the mechanical fan is and my bumper and winch and lights is covering up to much of the surface area of the radiotor and blocking air flow. so looks like I'm installing the datsun 240z louvers and hooking up my electric fan and hoping that it performs well enough trail to not overheat and not just keep the temps under control on the road.

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I believe I did. But I could be wrong, do you have the procedure.

 

Sorry, didn't catch this until today. Park your truck with the nose facing down hill somewhere and let it cool until you can touch the block. Pull the rear temp sensor at the back of the block. This is where air gets trapped. Once you have the sensor out, top off the coolant bottle until coolant starts coming out of the temp sender hole. If coolant isn't coming out, start the engine and let it warm up. Once it starts warming up, the coolant should start coming out. Once you start getting coolant, put the sender back in, and torque it to spec.

 

That about wraps it up.

 

Rob

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Yea but the also have a pull of 50 amps at start up, that is a bit much for my 60 Somthing amp alternator. Everybody just jumps and says put a Taurus electric fan in....... It's not that easy, to do it right the electrical system NEEDS to be beefed up to prevent failure down the road and a possible fire!

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Yes, they are big, fitment was a bi!^*h, and it's been a while since I put that fan in my Cherokee, several years in fact. My Cherokee had a "police" spec alt. (110 amps, I think) so I never worried about it, it was a public service vehicle in a former life. I do have to say that once I got the two relays figured out with the help of JP mag, you could not over heat that thing. You could actually feel the air draw from in front of the grill.

 

Eric

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It was not boiling over, and the reason is I turned it off before it got there, I do not want to blow a head gasket by letting it overheat all the way, However if I did not turn it off it would have gotten into the red.

 

I doubt it. According to your photos and time line, it sat and idled for forty minutes without overheating. In the last TWENTY MINUTES the needle barely moved. What makes you believe it would have gone into the red if you had let it go longer?

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