Overheating problem

[Thunderbear]

So coming home from work yesterday, going a little faster than usual, temp indicator creeps up to around 230. Not cool, literally. So I stop at O' Reilly s and pick up hoses and a thermostat, since I haven't replaced any of that since I bought it. Get home find out it's running straight antifreeze without a thermostat. Fine, replace hoses,t-stat, pcv, etc, and fix the mix with water. Start it, runs fine, go to work today and the thing damn near pegs the gauge at 260. No steam or anything, no oil pressure fluctuations, nada. Kill it, let it cool for five or so, and pop the hood. Still no steam, radiator is hot, but not burning hot, just hot to the touch. Bad CTS? I can't figure out why the gauge would peg without steam unless some weird air pocket developed somehow. Ideas?

[Backroads]

don't rule out a bad T stat from the store....been there done that. Gonna have to boil it to really know and make sure its opening. Had a similar situation where it would start, and idle and the temp would just climb and climb, I killed it before it blew the rad cap but knew it wasnt right, turned out to be a bad Tstat.

 

Only other thing I can think is a blockage somewhere. Those old rad hoses had the coil wires in them that are good for rusting and clogged stuff up.

[JeffN]

fill it from the metal tube off of the water pump, huge air pockets get there and will cause problems

[jimoshel]

Check the T-Stat first. Don't overlook the possibility of a bad temp sender or gauge.

[Pete M]

if a 4.0, you can bleed that last bit out with this technique:

 

-put on your safety glasses

-park it downhill (or with the back tires on ramps or a curb or whatever)

-let it cool completely

-carefully unscrew the temp sensor located at the top/back of the head (just enough to let air escape but not enough to remove it

-have someone (not you, so they can quickly kill the engine if a geyser erupts) start up the truck

-bleed the air out until there's no more air, add fluid as needed

[86FUBAR]

I had something similar happen once on my 2.8 manch after replacing the coolant and t stat and tried bleeding the air and I checked the t stat and replaced it a couple of times aswell and nothing helped. What I eventually did was drill a small 1/16 hole in the oute rim on the t stat and that solved that problem . I never before had such a hard time bleeding air befor that , that was annoying .

[Thunderbear]

New symptom, gauge = pegged, radiator cold to touch, but pressurized. Water pump dead?

[mvusse]

Thermostat stuck closed or low coolant level.

[Thunderbear]

Thermostat stuck closed or low coolant level.

 

Checked before I left, it was full both in the rad and the overflow.

 

Just boiled the thermo, it works. Replaced the CTS, upper rad hose, thermostat, and still overheats, according to the gauge. I'm leaning toward water pump and radiator, since they're the hardest to swap, of course.

[Pete M]

how long before the gauge pegged? did you try my bleeding procedure?

[Thunderbear]

how long before the gauge pegged? did you try my bleeding procedure?

 

15 minutes or so? Trip up the road and back. Finally pegged coming up the hill back home. Pulled in, turned it off, and touched the radiator. Half of the upper manifold on the left was warm, the rad cap was cold.. literally, cold. Opened the cap, spewed out cool coolant. Opened the water neck, pulled rad and heater hoses to check for obstructions.. nada.

 

Not yet, I changed the CTS and it spit coolant immediately, parked roughly level. Every time I crack a hose or opening.. it spits coolant, no air.

[mvusse]

Seems like you eliminated the other possibilities,so yes, probably the water pump.

[Comanche County]

Do Pete's method, best way to bleed the air,,,,but after you've bought a new radiator. I'm betting you need one.

[Thunderbear]

New radiator, same problem :wall:

 

Guess that means water pump.

[Comanche County]

Dang, guess I owe you a radiator.

 

I've seen pics of some that had corroded impeller blades on the water pump. Does it blow hot air from the heater? Perhaps the heater core is clogged?

 

Not suggesting any more, I may end up owing you an engine.

[Pete M]

in my experience, replacing the radiator is never a bad thing. :thumbsup:

[Thunderbear]

Dang, guess I owe you a radiator.

 

I've seen pics of some that had corroded impeller blades on the water pump. Does it blow hot air from the heater? Perhaps the heater core is clogged?

 

Not suggesting any more, I may end up owing you an engine.

 

It was spraypainted black, so it needed one anyway. Also, the last time I had it on the road, half of it was hot, and half cold, so I'm thinking it was clogged.

 

And no, I don't have heat now, but it was working back when it overheated. :fs2:

 

in my experience, replacing the radiator is never a bad thing. :thumbsup:

 

 

Righto.

 

Now, it's got a new CTS, new radiator, new water pump, and still overheating. :wall: :wall: :wall:

[mvusse]

And no, I don't have heat now, but it was working back when it overheated. :fs2:

 

Now, it's got a new CTS, new radiator, new water pump, and still overheating. :wall: :wall: :wall:

 

Burp the air out of the system.

 

By overheating, do you mean running over 210 degrees? (Which is not actually overheating and well within operating specs.)

 

Or do you mean needle pegged, steam coming out from under the hood and coolant boiling in the pressure tank?

 

Or do you mean 210 degrees, steam coming from under the hood and coolant boiling in the pressure tank?

 

Also, what do you use for coolant? Premixed? Tap water? Distilled water? Concentrate? Mix of any of these?

[Thunderbear]

And no, I don't have heat now, but it was working back when it overheated. :fs2:

 

Now, it's got a new CTS, new radiator, new water pump, and still overheating. :wall: :wall: :wall:

 

Burp the air out of the system.

 

By overheating, do you mean running over 210 degrees? (Which is not actually overheating and well within operating specs.)

 

Or do you mean needle pegged, steam coming out from under the hood and coolant boiling in the pressure tank?

 

Or do you mean 210 degrees, steam coming from under the hood and coolant boiling in the pressure tank?

 

Also, what do you use for coolant? Premixed? Tap water? Distilled water? Concentrate? Mix of any of these?

 

Overheating means temp gauge swinging well wide of 210 and approaching 260 with no sign of stopping. No steam, no boils, and the rad is cool to the touch when it happens. Oil still looks good, not toasted, and the truck idles just fine while the gauge pegs. I let it get to 240ish and kill it.

 

Coolant started out 100% antifreeze, with no thermostat, and an old radiator/cts/waterpump. Over the course of wrenching, it's been flushed to 50/50 antifreeze/distilled water.. probably closer to 40/60 coolant/water with spillage and refilling.

[mvusse]

Reason I asked is because a lot of people seem to think anything over 210 (even just a hair over) is overheating.

 

Sounds like you have an air bubble in the system now. There's a post somewhere on how to burp it, but I can't find it.

[Thunderbear]

I just noticed that midpoint is 220, haha. On my TJ, it's 210. So, after burping and refilling the radiator after it cools and settles. I have heat now, but it is still overheating. Interestingly, the heater increases in temp with RPM increases, and temp decreases when coming back to idle, while apparently only having a slight effect on the coolant temp. Upper half of the radiator is still cold to the touch, even after temp spikes. Temp gun says 57.9. On the CTS, it says 180ish. On the exhaust manifold, says 339, thermostat/water neck 154.

 

It seems to be improving, I now have heat. I keep refilling, and burping. Will continue to update...

[Thunderbear]

So, after a short drive up and down a local road, I'm working on the theory that the CTS is lying it's little copper @$$ off. It'll swing past 260, then drop down to 240 as I'm driving like it's giving the wrong temp readings. Temp gun says the CTS is 169, gauge says 260.

 

Still no boiling, no hesitation, oil looks great, and the rad is cold at 79 degrees. Water neck at 140ish. Exhaust manifold at 330ish.

[Automan2164]

Just interjecting here...

 

Unless you do the air burping method Pistol Pete laid out for you on a 4.0L, it will never be right. Especially on the Renix. I know of one local member to me who dealt with it for the longest time, and ended up selling the truck out of frustration. Many trucks I have looked at are the same thing too. the owner is selling it because they think the "Insert expensive part here" is busted, and they are done dumping money into it. Then they tell me they've replaced the radiator, hoses, pump, bypass, anything coolant related... It will start with one, then they usually replace everything because they are trying to chase down the problem they created by never burping it properly from the initial repair...

 

Also, a problem commonly overlooked (Although I doubt it here), is the pressure tank. Most are 20+ years old, and have cracks, bad caps, and the like. They never build pressure like they should, and the engines perpetually overheat.

 

Rob :cheers:

[HOrnbrod]

And after you've done all that, check for a clogged cat converter. If you still have one and it's the original, it's most likely clogged.

[Thunderbear]

Just interjecting here...

 

Unless you do the air burping method Pistol Pete laid out for you on a 4.0L, it will never be right. Especially on the Renix. I know of one local member to me who dealt with it for the longest time, and ended up selling the truck out of frustration. Many trucks I have looked at are the same thing too. the owner is selling it because they think the "Insert expensive part here" is busted, and they are done dumping money into it. Then they tell me they've replaced the radiator, hoses, pump, bypass, anything coolant related... It will start with one, then they usually replace everything because they are trying to chase down the problem they created by never burping it properly from the initial repair...

 

Also, a problem commonly overlooked (Although I doubt it here), is the pressure tank. Most are 20+ years old, and have cracks, bad caps, and the like. They never build pressure like they should, and the engines perpetually overheat.

 

Rob :cheers:

 

It's a 2.5, and I did Pete's method twice, just to be sure. I know how those guys felt. It's freaking maddening trying to nail down the problem with intermittent symptoms.

 

And after you've done all that, check for a clogged cat converter. If you still have one and it's the original, it's most likely clogged.

 

PO said it was new, for whatever that's worth. :ack:

 

I'm pretty sure it had a pinhole headgasket leak. After the test drive today, I came back to swap the CTS back, this time with the truck parked as usual facing uphill. I cracked the seal for the CTS.. no fluid. WTF? That can't be right, it should be pouring steadily out. I walked around and found that my right rear tire was doused in a mystery fluid, while my engine compartment was clean. No coolant smell, but I went back around to the engine and checked all the fluids, and they were all good except for the overflow tank. And as soon as I cracked it, I heard drip noises underneath. Put my hand on the block back by the firewall and found it wetter than $#!&. My thinking is that there was a small pinhole leak that evaded me when I was just idling it to check, and today's ride blew it out.