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Cooling System Overhaul - Stumped and Frustrated

Darren! (not that it would solv anything...) but you should ship that thing up here for me to put a 6.0 in it while me and Pinsco63 are doing a 6.0 in his 91! Oh if only...

If only i had the time to do that instead of the crate motor.....

Its all about priorities. I love this truck, but the 350 will do its job it if can keep it cool. Priorities currently lie in larger life goals, like the home purchase i'm working on.
 
Who needs a house?! Trucks are the important thing in life!


Im just kidding. I feel ya man. I have a ton of stuff on my list of wants. Knocking down the list of priorities is the challenge!
 
I know ever so just how you feel as far as the frustration. I fought my TBI idling bad for years until i gave up and did the 5.3. I literally did a 5.3 swap to fix an impossible idle problem.
 
SummitRacing sells radiator hose springs. Thought about you when I saw them listed just the other day when I was daydreaming about buying an aluminum radiator.
 
What are you guys using for radiator mounts for larger radiator's?

My mounts are kinda ghetto the way they are installed right now.

Looking for stock style, but with a deeper throat.
 
What are you guys using for radiator mounts for larger radiator's?

My mounts are kinda ghetto the way they are installed right now.

Looking for stock style, but with a deeper throat.


Anyone?

In addition, I ordered that lower hose spring, but also finally had a friend around to help me check if the hoses were collapsing.

My lower hose is plenty solid. Not going to install the spring til the next time i drain coolant. Not worth it. No way they are collapsing after revving it up for a while after driving the truck all day.

Going to pull the o2 sensor and "check" cat back pressure today when its cold. If its plugged, i have a guy in Sac that can slam a new cat in before my tow up the grade tomorrow. Otherwise, i'm just running with it again. Luckily, it will be much cooler outside this time.
 
do you have an engine oil cooler on this rig?


Yes Sir. Drivers side, in front of the rad.

IMG_2703.JPG


Factory oil cooler Drivers side, Matching trans cooler passenger side.
 
was just curious, as I know what happens to oil temps under a good load...

so we're still somewhat unresolved here right? ya think ya may have a plugged cat?
 
was just curious, as I know what happens to oil temps under a good load...

so we're still somewhat unresolved here right? ya think ya may have a plugged cat?


Totally unresolved, other than possibly too much blockage of the radiator with coolers. Although, many have the same config i have, cooler location wise.

Plugged cat is entirely possible. Have had various levels of fuel going through this thing, including full on black unburn fuel spraying out the exhaust at idle/warmup :haha:

So, plugged cat is fairly likely? Running out of options.
 
I've had the same issues with my 91 TBI454 C3500. It runs 210 unloaded on the freeway and with a load it will creep up to 230. I've tried the same "fixes" you tried. New WP, hoses, thermostat, big aluminum rad. ect. I think I may have finally found my problem and thought I'd pass it along.

While tracing the coolant flow, I found that the coolant flowing through the heater bypasses the radiator. It flows from the PS rad. tank, through the engine, back out the back of the block, though the heater core, and back to the PS rad. tank. This allows a large portion of the coolant to bypass any cooling at all.

I think that blocking the heater hose, forcing all coolant through the full radiator will solve my issue.

I'll post back when I've had a chance to drive it enough to give feedback
 
...While tracing the coolant flow, I found that the coolant flowing through the heater bypasses the radiator. It flows from the PS rad. tank, through the engine, back out the back of the block, though the heater core, and back to the PS rad. tank. This allows a large portion of the coolant to bypass any cooling at all.

I think that blocking the heater hose, forcing all coolant through the full radiator will solve my issue.

I'll post back when I've had a chance to drive it enough to give feedback

I don't think the coolant flow is quite that segregated. The coolant flow throught the block and radiator is failry turbulent. It is not at all like a portion of the coolant only circulates through the right side of the block and radiator via the heater core and never really migrates to the rest of the system (almost like a mini closed loop). The coolant is constantly flowing and mixing it's entire volume - and moving through the radiator.
If what you describe is true, it would be a complete design flaw pervasive among all GM systems with the same coolant flow. This is simply not the case. The overheating issue here is pretty unique.
 
I don't think the coolant flow is quite that segregated. The coolant flow throught the block and radiator is failry turbulent. It is not at all like a portion of the coolant only circulates through the right side of the block and radiator via the heater core and never really migrates to the rest of the system (almost like a mini closed loop). The coolant is constantly flowing and mixing it's entire volume - and moving through the radiator.

I'm still gonna try it. It just takes a minute to clamp off the hose, and it's free and just as easily undone.

If what you describe is true, it would be a complete design flaw pervasive among all GM systems with the same coolant flow. This is simply not the case.

I think it is a design flaw. I may be wrong, it's been known to happen. It's just that most of the non GM vehicles I've owned had valves that cut off the flow of coolant to the heater core when not in use.
 
I'm still gonna try it. It just takes a minute to clamp off the hose, and it's free and just as easily undone.



I think it is a design flaw. I may be wrong, it's been known to happen. It's just that most of the non GM vehicles I've owned had valves that cut off the flow of coolant to the heater core when not in use.
the only time I've personally seen the valve thing, was to be used with the AC. by keeping the coolant from circulating thru the heater core youre keeping the airflow a tad bit cooler. in fact most valves that are automatic, actually switch once the AC is turned to max cool, IIRC
 
My '89 has a vacuum controlled water valve inline with the heater hoses, it gets it's signal from the vacuum manifold setup at the heat level selector slide lever on the dash. More heat, the valve open more to let more water through, slide it to cold, it closes the valve completely.

I have argued with many people about this valve and how it's not factory, but I have had things torn apart on this truck several times, it's all factory run vacuum tubing.

Your overheating issue is different, I also have a dual cooler setup on the front of my radiator, just about identical to what you have, again, mine hardly rides over t-stat level and won't even reach t-stat levels in real cold weather.
 
I quickly went through the entire post and I think I have the gist of the problem and what you've tried/replaced to resolve the problem. The main problem I see is air flow on the radiator. As Fordum mentioned, you should try moving both the oil and trans coolers out of the way temporarily. Could probably do that with just a couple lengths of hose and couplers along with some simple brackets. It's cheap and shouldn't take that long to try this test.
I'd also remove the fan shroud and fan so you could measure the temps with your IR gun at different spots on the radiator while in your driveway. Maybe even take it for a drive before doing this so the tranny heats up. And as mentioned in this link, you can measure the temp of your cat to see if it's blocked. It says a difference of 200* between the inlet and outlet means that it's blocked (or a pressure reading at the O2 sensor of 4 or 5 psi).
http://www.buzzle.com/articles/clogged-catalytic-converter-symptoms.html

As a final thought, it seems like you've dumped a lot of $$ into replacing parts but you don't want spend the money on a fan cooled trans cooler. I think they're a wise investment to make sure the trans stays cool. Not only does it move it away from in front of the radiator where it's restricting air movement and blowing very hot air onto it, but I think they're more efficient.
 
I quickly went through the entire post and I think I have the gist of the problem and what you've tried/replaced to resolve the problem. The main problem I see is air flow on the radiator. As Fordum mentioned, you should try moving both the oil and trans coolers out of the way temporarily. Could probably do that with just a couple lengths of hose and couplers along with some simple brackets. It's cheap and shouldn't take that long to try this test.
I'd also remove the fan shroud and fan so you could measure the temps with your IR gun at different spots on the radiator while in your driveway. Maybe even take it for a drive before doing this so the tranny heats up. And as mentioned in this link, you can measure the temp of your cat to see if it's blocked. It says a difference of 200* between the inlet and outlet means that it's blocked (or a pressure reading at the O2 sensor of 4 or 5 psi).
http://www.buzzle.com/articles/clogged-catalytic-converter-symptoms.html

As a final thought, it seems like you've dumped a lot of $$ into replacing parts but you don't want spend the money on a fan cooled trans cooler. I think they're a wise investment to make sure the trans stays cool. Not only does it move it away from in front of the radiator where it's restricting air movement and blowing very hot air onto it, but I think they're more efficient.


Thanks for the input. I'll drag my IR gun with me again, hadn't thought of checking inlet/outlet temps on the Cat. Good idea.
 
A properly working cat should be about 100* hotter on the outlet than the inlet. If the inlet is a lot hotter than the outlet, it is probably restricted.
 

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