Tech: At wits end with an overheating motor, long post

BUG-E J said:

Water pump was mentioned pretty early. He keeps shooting that down....

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I don't keep shutting it down, it's my next test point. What I keep "pointing out" is that I had all my old cooling system stuff still in place and it began overheating. Which is why I wouldn't think the water pump initially as the old one was working seemingly fine before. That's why I kept looking at everything else as well. I agree that I hope it's the water pump. I've got a new one sitting right here in the shop ready to swap out.

Today I ran it with the cap on, and barely made it around the block before it hit 210 in under 3 minutes. A buddy pointed something out, with my new radiator setup, when the T-stat opened I should notice a temp drop for a few seconds while the cool radiator fluid moves into the engine. It doesn't, it stays hot and gets hotter.

Did the exhaust gas test today and it passed, no exhaust gasses detected. So my next plan is to remove the T-stat and then remove the top hose. Fire up the engine and it should pump all the water in the radiator right out of the hose. That should give me a good indicator of flow from the pump before I pull the whole front end off. 've got to take my entire front end down to get the water pump swapped out as all my March performance pulley brackets use the WP as a mount point. Thus why I wanted to eliminate everything before I went back to square one.

whoops double post

Re:

Have you checked both radiator hose's to see if you can feel a temperature difference

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I have been reading a bit and every day that I read it reminds of when I did a big block swap in my blazer when I was 20yrs old.

Coming from a 305 to a 402. I dropped that thing in using the big block temp sensor because the threads between the 2 cylinder heads were different. Never thought twice about it

You said you already verified your gauge and sensor function.

I just remember doing exactly what you did. Crank it up, drive around the block and the gauge says 230. I'm freakin out cuz its a brand new build

I tried all of the obvious things like you, airflow, air bubbles, t stat change etc..

I ran without a t stat around the block, didn't change.

I borrow a laser thermometer from an old man at the parts store, motor was running at 130 degrees the whole time. The temp sensors are different yet look the same.

So, only thing you did was re wire the rig. Try to remember not to grasp for straws. Go back to the basics and you'll find your problem.

customcj7 said:

A buddy pointed something out, with my new radiator setup, when the T-stat opened I should notice a temp drop for a few seconds while the cool radiator fluid moves into the engine. It doesn't, it stays hot and gets hotter.

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Your buddy is smart. Even the most piss poor cooling setup will show a temp drop once the thermostat opens for the first time and the room temp water flows into the hot block.

LightBnDr said:

I have been reading a bit and every day that I read it reminds of when I did a big block swap in my blazer when I was 20yrs old.

Coming from a 305 to a 402. I dropped that thing in using the big block temp sensor because the threads between the 2 cylinder heads were different. Never thought twice about it

You said you already verified your gauge and sensor function.

I just remember doing exactly what you did. Crank it up, drive around the block and the gauge says 230. I'm freakin out cuz its a brand new build

I tried all of the obvious things like you, airflow, air bubbles, t stat change etc..

I ran without a t stat around the block, didn't change.

I borrow a laser thermometer from an old man at the parts store, motor was running at 130 degrees the whole time. The temp sensors are different yet look the same.

So, only thing you did was re wire the rig. Try to remember not to grasp for straws. Go back to the basics and you'll find your problem.

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This is a good point as well. Could be a bad gauge or sending unit.

Long time ago I was curious of a pump working like we are here....
On my setup, yours may be different, with the radiator cap off you could watch and see the water start churning when the t-stat opened. Pretty much let's you know it's pushing water. Now, I don't know what the gpm was but it was good enough info for me that the pump works

I'm betting, more like hoping that some of you were right and some asshat put the wrong pump in the box. After talking to my friend last night about the issue and his mention of the temp drop, and then Rocktoys asking about the hoses, I'm betting waterpump.

Upper hose is hot as balls, and if I remember correctly, so was the lower. I remember checking a few days ago, but not 100% sure.

Sending unit and Temp gauge check out as I've verified both with an Ohm meter. Sending unit was monitored at cold, to warm, to hot on the ohm meter and was within the specified ranges. Was on the phone with Autometer verifying their guage as well.

EDIT: Yeah I can see slight movement from the radiator cap, but churning is about as far from the adjective as I would use. Moving is about it.

customcj7 said:

I'm betting, more like hoping that some of you were right and some asshat put the wrong pump in the box. After talking to my friend last night about the issue and his mention of the temp drop, and then Rocktoys asking about the hoses, I'm betting waterpump.

Upper hose is hot as balls, and if I remember correctly, so was the lower. I remember checking a few days ago, but not 100% sure.

Sending unit and Temp gauge check out as I've verified both with an Ohm meter. Sending unit was monitored at cold, to warm, to hot on the ohm meter and was within the specified ranges. Was on the phone with Autometer verifying their guage as well.

EDIT: Yeah I can see slight movement from the radiator cap, but churning is about as far from the adjective as I would use. Moving is about it.

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I can not tell you how many times I have seen a wrong direction wp issue with a sbf when I worked at a parts store. Once a month at least

"Sending unit and Temp gauge check out as I've verified both with an Ohm meter. Sending unit was monitored at cold, to warm, to hot on the ohm meter and was within the specified ranges. Was on the phone with Autometer verifying their guage as well"

I have had the same problem since I bought my Jeep with my Temp Gauge and Trans Temp gauge from autometer. I have Ohmed them both and replaced sending unit sensors and they both still read wrong. I called Autometer and checked them just like they said. My Coolant reads to warm and will get to 250 on long hill climbs but, my Trans temp barely reads unless I`m on a long hill climb and even then it never gets above 140*. I finally got a temp heat gun and after the long hill climb in Harlan coming from the Putney side to middle fork (yall know that's big one) my Coolant gauge was pegged out and trans was like 130* on the gauges. I jumped out and shot temps all over the motor (rad hose, temp housing, trans pan, coolant lines etc) and my coolant was actually 190* and my trans was 180*. Perfect. I stopped even looking at the bastards. Gonna eventually put manual autometer gauges in it for those two but, just haven`t done it yet.

I'm not even running guages on my next rig. When you see steam from the radiator youll know it's hot.
Tranny temps vary depending on guage location. They are usually really hot and make you want to baby it around. Oil pressure is about the only one I care for

All right, so I removed the thermostat, and then ran a hose to see if the water pump would pump out water. I took video of it, and it looks like it is pumping, but you tell me. It's stayed around 150 to 160° the whole time, so I reconnected the hoses and took it for a drive. It took some time but then it overheated. It did not boil out but the gauge was near 250. So I stopped.

Engine running

You can see in the video where I kink The hose, and it pops out in waves, I then added water back in and got a steady stream.


Or is this what cavitation may look like?

jam nut loose on alt brace

The way the nozzle off the garden hose is sealing in the top of the radiator the pressure of the water supply from the house may be what's forceing the water throught the engine. Will the engine pump out the water if the radiator is just maintained full without the pressure from the house?

That's what I did in the video, I kinked the hose to shut off Flow. And that is where I get the intermittent flow of water, which is curious to me

Tomorrow I'll cap The inlet high side of the radiator and fill it with water, and then start the engine to monitor flow

Im thinking you are not getting good flow from the water pump.
You have good air flow with the new fan. Overheating happens fairly quick so it's not from a lack of capacity in the system. That brings it to water flow. Correct pump rotation, belts not slipping, restricted plumbing/thermostat.

Re:

But the cold water out of the hose could have kept the temperature down.

How hot has it gotten and did you ever use a laser thermometer to check temp of the engine.
Could stick a thermometer in the radiator to check temp.

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Trying to pick up a laser thermometer today. I wondered if a Grill thermometer in the radiator fluid would work since it gets so high.

Is the water pump really hard to take off?

Re:

Yes it will. Have you ever let rum to see if it would push water oit from running hot? I understand you may not want it.

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