Coolant System: Re-visiting

#1
So I posted about a month ago on my rig getting a little warm. It was recommended that I replace the radiator.

So I did, old one was a 3 core, put in a nice, new aftermarket 4 core radiator. Thought all would be well...but it isn't. Drove the truck all the way to Morris Mountain on Sunday. On the way out, top speed was limited to 60 mph to keep the temps under control. On the way back, more like 55 with two cool off stops.

On the trail, no problems. Stop and go traffic and errands, ok. Only while on the interstate is there a problem.

BTW on the highway, I'm turning middle of the road RPMs, like 2500~3000 at my 60-ish mph (from what I've gathered from basic research). BTW, truck does redline at 4400 rpm :la:.

Here is what has been done: Rebuilt water pump, new T-stat, new radiator and fresh coolant. I have a mechanical fan, but no clutch (fan is bolted directly to the water pump pulley). Belt feels tight and belt is fairly new. I have most of a radiator shroud. Some of it was "deleted" because it is a Grade A Pain in the *** to remove if its all there. Oh and a new radiator cap was installed with the radiator. I don't have new hoses, but they are all in good condition. There is no fluid leaking.

Engine side, I haven't fooled with the carb recently but it was good last time I checked. Ignition is in good condition and properly timed. Engine isn't making any unusual metallic noises...for the first time in...FOREVER :la:

Lastly, except for what is mentioned, the system is STOCK. Engine is modified, probably where I'm getting my extra heat from but nothing that should cause a problem and certainly all of it has been done before. So There isn't any mickey mouse work in there, with custom hoses or sideway mounted radiator or anything like that. Except for the oil cooler, there isn't anything blocking the radiator.

So here is what I'm thinking I need to do and wanted to check with ya'll first. Its been my observation that normal people traditionally have a better grasp on what is happening compared to the "specialty" guys (aka, rover people).

1. Check to make sure the SOB isn't running lean. Checked it a while ago and don't remember any problems. Spark plugs looked good when I pulled them on Saturday. However I've got a colortune so that will tell all. Maybe look into tuning the truck to run just a touch rich?

2. Try the coolant additive snake oil. I mean, why the hell not.

3. Check the see if my gauges are accurate. My oil temp gauge is capillary so I believe it but my water temp is 40 years old, British and Electrical...nuff said :la:. I'm probably going to buy/liberate a laser temp sensor to see whats going on under there. See if the SOB actually IS actually running warm.

4. I really don't want to do this, but will if I have to: Pull the oil cooler and have it hot dipped and checked. Also might look into replacing it. Something tells me that oil cooler designs have gotten a lot better in the last half century.

5. Maybe...maybe not...pull the T-stat. I'll be golden until October when it isn't buzzard sweating hot outside. People have cursed at me for saying this but hey, its designed to restrict flow...something I don't want right now. Is this sound thinking or am I being stupid?

6. Maybe try and track down a decent fan shroud for the stupid thing.

7. I don't think I have a bubble in the system and I would've thought that after over 200 miles the stupid bubbles would've worked their way out.

8. Side note: The system seems to be under a lot more pressure than usual. I pull the cap off and a little bit of fluid always shoots out from the radiator cap (BTW, only check it when the truck is cold, as in, sat overnight/couple of days in the shade). Does this tell anyone anything?

Any input on this subject would be appreciated before I start throwing anti-freeze everywhere. I just want my old POS running smoothly again and now that cruising on the highway is an option again, more wheeling is also an option. Only thing holding me back is this heat problem.

Thanks ya'll.
 
#3
Both. The Water temp, while it doesn't have numbers, is always in above the half way mark, but below the redline. The oil temp, I try to keep it around 85 degrees C and when it gets a touch above that, I start to worry.
 
#4
On the trail, no problems. Stop and go traffic and errands, ok. Only while on the interstate is there a problem.
what about if you were to rev it up for a while similar to interstate driving on the trail, does it overheat? I wonder if there is some sort of air pocket forming on the interstate behind your arb bumper that is not letting air flow through the radiator, like it just wants to go under or over the truck?
 
#5
Have you checked your ignition timing yet?

I would also check the coolant for combustion gases. You can do this with a simple tester from the parts store. In my last car, I had an overheating issue that wouldn't go away despite replacing the radiator, water pump, etc. It turned out that I had several small cracks in my cylinder head that were causing the overheating issues.

Removing the thermostat will not stop your rig from overheating, it will only delay it. With the thermostat out of the loop, there will be more coolant to heat when you first fire it up in the morning. It will take longer to warm up, but eventually it will still reach the same temps.

...I would start with the ignition timing though.
 
#6
Already checked the ignition timing. I'm right at 6 degrees BTDC, right where I need to be for running the "good" fuel here in the US.

Cylinder head and block have been checked recently by a machine shop. If there was a problem, I would assume they would say something about it.

Will go forage for the combustion tester. Decent place to start!
 
#7
I'm wondering if, because of the mods, you're not moving enough coolant around, ie, is the pump big enough to move the necessary coolant needed to cool the engine.

A cooling system, as you know, has numerous parts that must all function in unison, otherwise overheating will occur.

I would certainly consider removing the t-stat from the equation to see if it's restricting the flow.

JP
 
#8
I'm wondering if, because of the mods, you're not moving enough coolant around, ie, is the pump big enough to move the necessary coolant needed to cool the engine.

A cooling system, as you know, has numerous parts that must all function in unison, otherwise overheating will occur.

I would certainly consider removing the t-stat from the equation to see if it's restricting the flow.

JP
Or take the gas cap off and replace everything underneath it:grin:
 
#9
Or take the gas cap off and replace everything underneath it:grin:
Sure! I'm cool with that! I assume I can use your garage space for however long it takes me to swap in a powertrain out of an early 2000s chevy...right?? :flipoff:

After more research, I'm seeing a lot that says, check gauges for accuracy. I seems like that is the first thing on the list, then go from there.

BTW, I DID overheat and melt pistons about 2 years ago so yes, I am a little timid on the subject. No, I have no desire to replace more engine components.
 
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