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Overheating

2K views 38 replies 8 participants last post by  onevision 
#1 ·
So I’ve been having some overheating issues that I just can’t seem to nail down the cause or a solution to fix it and was hoping to tap into someone’s expertise and experience to chuck this dog a bone and point me in the right direction. Basically it runs fine and from a cold start and it warms up normally as you’d expect until it gets up to normal operating temperature. It will stay at running temperature for a short while, the length of time determined by the type of driving. Highway driving is the worst with temperature steadily increasing until shutdown. Driving around town doesn’t heat up as quickly, but eventually will overheat as well and idling for the most part seems to stay within operating temps. So the temperature is 210 F with the gauge straight up and I turn the engine off if it reaches 225 - 230 F.

A little background - This is on my 1998 Grand that I just upgraded from a 5.2 to a new rebuilt 5.9 magnum engine running a high compression setup (Edelbrock heads). I also upgraded the radiator and put on an electric fan with an aftermarket wiring solution. The cooling fan kicks on exactly as it should and there doesn’t seem to be an issue in how that operates. In the process of eliminating any possible causes I did have the cooling system power flushed, which made no difference. Also changed out the thermostat for a new one 3 different times, one of those times I used a 180 degree thermostat and the other 2 times using a 195 F. I should also mention that the main display pops up a warning after the engine has heated up, stating “Bad coolant sensor”. The error comes and goes - kind of like it’s a loose wire tripping it and I have changed the coolant sensor a total of 3 times as well. I also have tried burping it many times, but have had mixed results, none solving the issue. Took it to the dealer, where they did find an air pocket in the radiator and expelled it, but problem still exists. Tried drilling a small hole into the thermostat, but it had little effect.

Any ideas? So I had some question on burping and wanted to make sure this is expected behavior. So burping seemed to go as expected for the first opening of the thermostat, but from that point forward it really struggles to cycle and even on the first time it happens when it hits about 210, instead of around 195, which is what the thermostat is rated at. Also if I give it a little throttle, then things will constantly drain. I realize that the system was designed to work under pressure, but wasn’t sure if that was expected behavior. Any help at all would be greatly valued.
 
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#3 ·
#8 ·
Wingless is talking about the tar paper on either side of the radiator not the rubber sections in the niner shroud.

Not that those missing would be enough to do what the OP is describing.
 
#9 ·
When I did my 5.9 swap, I ran the 94 grand radiator and all cooling system s with that year. They were all brand new, water pump, radiator, fluids, hoses, thermostat...and I never had an issue. I also didn't have the stock, tar paper in under the hood splash guards.

Hunter
 
#10 ·
Thanks for the post and I apologize for the delay in my response. It certainly doesn't hurt to verify that I've put the correct parts in, so would be happy to clarify in more detail what I've installed and am using My setup is using a replacement radiator from Radiator Express for the 5.9 and I'm using a Zirgo aluminium fan shroud that supports a 16" Zirgo fan rated at 3000 fCFM. All of this is controlled by the Flex-a-lite speed control module, which I've linked to each of these below if you want more detail. From what I understand these should all work as suitable replacements.

Radiator Express - radiator
Aluminium fan shroud
Cooling fan
Flex-a-lite control module

That's interesting about the "Coolant sensor bad" that pops up and I was unable to find any reference to it in the Jeep service manual, which is pretty complete as an information source. I'm a little confused though following that other thread link - so is that what one person did to fix that from displaying? Am I correct in believing that the pink and black wires he's talking about are the input from whatever (I believe the coolant temperature sensor on the engine) and it is prone to shorting at that connection?
 
#13 ·
The display is connected to the coolant LEVEL sensor in the overflow bottle. It has nothing to do with the temp sensor that the PCM/dash use. The solder joints crack and they create a loose connection, which causes the VIC to think the sender is bad. Fix the solder joints and the message will go away.

Again this is 1000% a separate issue from your overheating.

The issue looks like that fan, 3000 cfm is not near enough to keep these engines cool. The niner e-fan was well over 3000 cfm on low, and twice that on high. The taurus and mark8 fans that most people swap in are about the same CFM as the niner (same motor, different blade design).

So you need a beefier fan, what did you do for a shroud?
 
#11 ·
You mentioned it's a restriction at highway speeds and I wanted to understand more as to why that would be? You'd think that with the increase of air just naturally hitting the radiator from the speed of travel, that would help cool the engine rather than restrict cooling, right? Or are you saying - for example, a low CFM fan or even possibly wrong feed type/direction would actually block the air flow or even cause some type of cancelling effect? I just posted the details of parts used.
 
#14 ·
So correct me here if I'm wrong, but I believe the Lincoln Mark VIII can is a two speed fan, which I'm under the belief that the wiring setup is different. The flex-a-lite control module that I'm using will do variable speed between 60-100% as needed, so I don't know if the two would be compatible. I'm not familiar with the other fan you mentioned, but will look that up.

Right now I have an aluminum fan shroud, which was linked in my previous post. My radiator is all aluminum including the side pieces.



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#15 ·
#19 ·
That's great to know and I'll give that a shot. Thanks for the invaluable information

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#16 ·
Just out of curiosity.....what kind of thermostat did you install? I have had very very bad issues with Motorads purchased at O Reilly.

Same with their radiator caps. I mention the radiator cap, because as the engine runs, it gets hotter, thermal expansion will push back the cap spring, and cause a loss of pressurization, causing a running hot issue. Motorad's radiator caps seem to have very weak springs in them causing this issue. Both of these items, I now purchase at the dealership, no more troubles.

Tim
 
#18 ·
Funny that you should mention that, as I've had some inconsistent results using the thermostats from O'Reilly, and always on the lower end of the scale. I'm not sure the brand, but it's a blue and white box that it comes in - I'll check when I get home tonight.

The radiator cap is exactly as you mentioned and while it passes a pressure check it does also leak pressure out and only barely passed

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#20 ·
Mark VIII would be my choice, as the Taurus shroud is a few inches smaller and has a smaller blade I believe . I bought a mark viii setup on eBay and replaced the motor with a vdo 9027. There's a seller on eBay that has them for $52 plus shipping. Had to grind off the rivits and use new bolts for the new motor. Wish I still had the niner shroud, but the po tossed it.


You'll have to loosen the upper rad support to get the mark shroud in there. Took some frustration before I realized that.
 
#27 ·
Mark VIII would be my choice, as the Taurus shroud is a few inches smaller and has a smaller blade I believe . I bought a mark viii setup on eBay and replaced the motor with a vdo 9027. There's a seller on eBay that has them for $52 plus shipping. Had to grind off the rivits and use new bolts for the new motor. Wish I still had the niner shroud, but the po tossed it.

You'll have to loosen the upper rad support to get the mark shroud in there. Took some frustration before I realized that.
What year Mark 8? There seems to be quite a distance between years with some being as low as 2500 cfm at high speed.

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#21 ·
Yeah, if you can't find a niner shroud the markVIII is the next best thing.

You could probably use the volvo fan with your current shroud though.
 
#24 ·
Why wouldn't my current aluminum shroud work? Is the mounting of the mark VIII so different?

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#22 ·
So during this whole process I noticed that this 5.9 engine does seem to run at a hotter temperature than the 5.2, which already ran pretty hot. I was thinking about adding a hood vent to help evacuate some of the heat buildup in the engine compartment. Does anyone know of a good good vent?

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#23 ·
A 5.9 really shouldn't run much hotter than the 5.2 with the same cooling system.
 
#25 ·
The MarkVIII setup is shroud and fan, the point being that the shroud fits our radiators pretty well.
 
#26 ·
Gotcha, that makes sense

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#28 ·
93-96 with the 5.0 V8. Maybe the smaller engines as well.
 
#30 ·
Yeah, I was looking at that one - super nice that they give 1/2" of wire lead to wire to. Lol They all kind of look the same though, but from other resources it seems the CFM varies quite a bit

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#32 ·
So an update to this problem that is trying to kill me. I've worked through most of the problem and currently things mostly work. I did order a Mark VIII fan and shroud which I installed and have to say that it noticeable pushes more air than the fan I was using. Ended up switching back to the thermostat located in the upper radiator hose rather than using the one provided by the flexlite kit that controls the fan and goes into the radiator vents.

Still have one major issue however. It seems to control the temperature very well just driving around, but once I get it on the highway or take it over 50 mph, it overheats. It will run consistently at 220 and doesn't seem to get hotter, but that's still a bit too much for normal running. The fan control system has a manual override to just turn the fan on all the time, which with that forcing the fan on I'm able to maintain that 220. Any ideas on what could be causing this and why it's only a problem at freeway speeds?

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#34 ·
Yeah I was kind of wondering the validity of the in vehicle gauge. It's just using the stock dash gauge which I've never found to be all that accurate. I have one of those infrared thermometer guns, but I'm not sure where to shoot the laser at to get a good reading. It's the engine thermostat that really small one on the top right by that intake manifold? And would that be a good place to get a reading, or is it not possible to get a good reading using one of those?

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