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Discussion Starter · #1 ·
OK, I know this has been mentioned before over the years, but I don't want to resurrect an old thread and I haven't found specific mention of anyone doing exactly what I've done... So I'm working on one of my good customer's '96 K2500 Sub, lots of little things to take care of, replaced crank balancer, resealed the leaking block heater, got the starter, PS pump and front driveshaft rebuilt. Went through the IP again because he's been complaining of a hard start hot, so it's fresh with new low friction poppet valve kit and FSOL coil. I've already upgraded to the dual T-stat housing and HO water pump but they work this truck hard and I've been wanting to do a cooling mod like this for ever and finally have a good opportunity.

So most of you probably know about GM 6.2s and 6.5s coolant flow problems and their tendency to run much hotter toward the back 2 cylinders. GM's "fix" for this problem was to overbore 7&8 a little to allow for more thermal expansion, but obviously fixing the problem rather than covering it up would be better. There are a few kits on the market sure, but they seem a bit over priced but a big thanks to Paradox by Design for writing a detailed article on the subject. I like their idea, but I don't see why you need those types of fittings for coolant, I mean the rad and heater hoses work fine with just hose clamps, its only ~15psi pressure why all the expensive high pressure fittings for their kit?? Also, rather than plumbing the stagnant coolant to the TSTAT housing like they did, I decided to go from the rear plates right to the WP suction side for 2 reasons, first to increase circulation even while the stats are closed and 2 because, well, its convenient, there's a pipe plug right on the WP so makes that part really easy too. So here's what I did...

I pulled both rear coolant block off plates, drilled them through the center and tapped them to 1/4" NPT. Then I installed NPT to 1/2" hose barb brass fittings with teflon tape and belt sanded the back side where they were sticking through they are flat on the bottom side. I removed the 1/2 pipe plug from the pass side top of the water pump and installed a 1/2"NPT to 1/2" barb brass fitting. Then I just connected all 3 with 1/2" heater hose and a 1/2" brass hose tee and followed righ beside the heater core hoses. All it took was 4 fittings, 6 hose clamps and about 5ft of 1/2" hose. I haven't filled it up and tested it out yet, but it looks great, I'll get some pictures Monday when I get back to work. I will use a vacuum fill method to eliminate virtually any air bubbles when I fill it up and maybe even get some pictures with the infrared camera to judge how its working.

Here's the fittings purchased...
total cost for parts was under $40.
642331
642332
642333
 

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pretty neat! let us know how it works- i'm very interested to see where this goes.
 
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1995 Chevrolet Silverado Z71 6.5 TD
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Went to the paradox website, they had a tech article on how to remove a swollen glow plug, no broken yet. It was great advice in my opinion. I haven't seen or heard of that procedure to remove a swollen GP. Scroll down and read the procedure.
Paradox By Design tech articles & how-to write ups
 

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Discussion Starter · #5 · (Edited)
I'm hoping to test it soon, I've got a thermal imaging camera so hopefully I can "see" the difference it makes.

Have to take care of some other unrelated issues, the shifter cable keeps falling off and there's something up with the brakes, once I get that straightened out then I'll be able to test drive it more.
 

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Discussion Starter · #6 · (Edited)
I have done a little road testing and it looks very good so far. Checking the block at 4 corners just below head, i'm only seeing a temperature difference of like 5 degrees from any 2 corners. Coolant temp is rock steady at 185 and after driving 20 mins at highway speed the coolant system has virtually no pressure on it at all. Ambient temperatures are pretty cool right now, but it looks promising, can't wait for them to try it out in the sumer months.
 

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I have done a little road testing and it looks very good so far. Checking the block at 4 corners just below head, i'm only seeing a temperature difference of like 5 degrees from any 2 corners. Coolant temp is rock steady at 185 and after driving 20 mins at highway speed the coolant system has virtually no pressure on it at all. Ambient temperatures are pretty cool right now, but it looks promisting, can't wait for them to try it out in the sumer months.
Beta test results sound great. Like you mentioned it will be great to see the data once your out driving during the summer months. Promising info, awesome.
 

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Discussion Starter · #8 ·
Yeah, I usually see this suburban once every year or two for various things so I'm trying to be as sure as possible that these modifications will work properly...

I've been thinking, what if I were to route the coolant back to a tee where the temp sensor is in the coolant crossover instead? That would be just as easy to do, and that would send heated coolant from the back of the heads out to the upper rad hose / outlet instead of back in the lower rad / inlet.
 

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Yeah, I usually see this suburban once every year or two for various things so I'm trying to be as sure as possible that these modifications will work properly...

I've been thinking, what if I were to route the coolant back to a tee where the temp sensor is in the coolant crossover instead? That would be just as easy to do, and that would send heated coolant from the back of the heads out to the upper rad hose / outlet instead of back in the lower rad / inlet.
The water coming from the rear head area should be circulated back to the radiator for cooling correct.
 

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Discussion Starter · #10 ·
The water coming from the rear head area should be circulated back to the radiator for cooling correct.
Yes, I think that's the "correct" answer. I was debating this plan a lot while I was planning it, let me explain my reasoning and see if it holds water...
My main goal with this mod is to improve coolant flow at the rear of the block. So first imagine what the flow looks like with the T-stat closed... water is pushed into the front of the block and some of it flows out of the tapped plates at the back of the heads, through the 1/2 hose I added into the water pump inlet. Here the heated water mixes with cooler water from the radiator and is pushed back into the engine and closed cycle repeats. This flow should make the engine warm up to operating temperature more evenly.
Now when the thermostat opens things get more interesting. Yes, this will mix hot water from back of the heads with cooler water returning from the radiator which means the water temp at the WP inlet will be higher. This also means the volume of water from the radiator will be lower. I cannot deny those 2 facts but in defense I will say that it's only a 1/2" hose, which is tiny compared to the 2" or whatever the water pump inlet is. It doesn't seem like enough to cause a serious decrease in flow through the radiator.... does it?

What other ways to test this should I try and should I limit or reroute bypass coolant flow??
 

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Yes, I think that's the "correct" answer. I was debating this plan a lot while I was planning it, let me explain my reasoning and see if it holds water...
My main goal with this mod is to improve coolant flow at the rear of the block. So first imagine what the flow looks like with the T-stat closed... water is pushed into the front of the block and some of it flows out of the tapped plates at the back of the heads, through the 1/2 hose I added into the water pump inlet. Here the heated water mixes with cooler water from the radiator and is pushed back into the engine and closed cycle repeats. This flow should make the engine warm up to operating temperature more evenly.
Now when the thermostat opens things get more interesting. Yes, this will mix hot water from back of the heads with cooler water returning from the radiator which means the water temp at the WP inlet will be higher. This also means the volume of water from the radiator will be lower. I cannot deny those 2 facts but in defense I will say that it's only a 1/2" hose, which is tiny compared to the 2" or whatever the water pump inlet is. It doesn't seem like enough to cause a serious decrease in flow through the radiator.... does it?

What other ways to test this should I try and should I limit or reroute bypass coolant flow??
I was thinking of doing the same thing but returning the coolant to a T in the heater core return line. This would bypass the thermostat and take a little longer to warm up, but I think the added heat rejection would be well worth it in the long run.
 

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1995 Chevrolet Silverado Z71 6.5 TD
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Yes, I think that's the "correct" answer. I was debating this plan a lot while I was planning it, let me explain my reasoning and see if it holds water...
My main goal with this mod is to improve coolant flow at the rear of the block. So first imagine what the flow looks like with the T-stat closed... water is pushed into the front of the block and some of it flows out of the tapped plates at the back of the heads, through the 1/2 hose I added into the water pump inlet. Here the heated water mixes with cooler water from the radiator and is pushed back into the engine and closed cycle repeats. This flow should make the engine warm up to operating temperature more evenly.
Now when the thermostat opens things get more interesting. Yes, this will mix hot water from back of the heads with cooler water returning from the radiator which means the water temp at the WP inlet will be higher. This also means the volume of water from the radiator will be lower. I cannot deny those 2 facts but in defense I will say that it's only a 1/2" hose, which is tiny compared to the 2" or whatever the water pump inlet is. It doesn't seem like enough to cause a serious decrease in flow through the radiator.... does it?

What other ways to test this should I try and should I limit or reroute bypass coolant flow??
No it doesn't seem like the hot or warmer water flow from the 1/2" hose when mixing with the water from the 2" in the wp inlet will over saturate the incoming cooler water. The testing your doing now and during the summer will either show success or not failure but I believe a stable temp whether higher which I doubt but possibly lower than what the water temp before you installed cooling mod. You did state that the rear temps taken with a infrared meter was at 180 on both corners correct. That in itself is a improvement.
 

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Discussion Starter · #13 ·
...You did state that the rear temps taken with a infrared meter was at 180 on both corners correct. That in itself is a improvement.
Yes, I will try to remember to get the pictures off of the thermal camera to prove it, but yeah, its hard to see a temperature differential looking at the side of the block... of course its a little hard to see with the stuff in the way but, still, I think I'm on the right track.
 

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No proof needed bro, I was merely making conversation with in my reply to you. all good.
 

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Nice mod! I have this mod on my to-do list for my K30. I already had block-off plates laser cut to weld bungs on to. I'm about to add this mod to my friend's K30 that is in my care, but I am unsure what hose size to go with.

Why did you choose 1/2 hose? The Paradox kit looks much smaller, 1/4 or even 3/16?
 

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Nice mod! I have this mod on my to-do list for my K30. I already had block-off plates laser cut to weld bungs on to. I'm about to add this mod to my friend's K30 that is in my care, but I am unsure what hose size to go with.

Why did you choose 1/2 hose? The Paradox kit looks much smaller, 1/4 or even 3/16?
I figured he wanted to remove as much hot water as possible from that area for cooler rear head area.
 

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I figured he wanted to remove as much hot water as possible from that area for cooler rear head area.
That much I figured :LOL: But Paradox must've chosen their sizes for a reason, they've done the testing, or at least claim too. Maybe there's a "scientific" reason the OP chose 1/2 hose...
 

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Discussion Starter · #18 ·
That much I figured :LOL: But Paradox must've chosen their sizes for a reason, they've done the testing, or at least claim too. Maybe there's a "scientific" reason the OP chose 1/2 hose...
Perhaps "scientific" isn't the correct term... Yeah they chose very small hoses and claimed larger hoses caused "over cooling". I mean, who am I to argue, they have way better equipment than I do to test... I just don't see it. I reasoned that standard 5/8" heater hose would be overkill and I was debating between 3/8" and 1/2" for a while. I just didn't see how a single 3/8" hose could flow enough to make difference, but if I was wrong and 1/2" was indeed too large, I could easily restrict it.

There you have it, my "scientific" thought process (more like S.W.A.G.) Actually what made me even start thinking about it was just noticing the pipe plug on the water pump on the previous 6.5 I worked on.
 

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I think you may end up restricting it down. 1/2" seems like too much flow to me. Moving coolant too fast thru an engine is just as bad as too slow. But i like your idea. Easy and cheap to make. As you said adding a restrictor is no big deal. Interested to see what an IR gun says on different parts of the head when the engine has been put to work.
 

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I think I'm going with 1/4 myself. Still a little bigger then Paradox's? The more I look at their kit, the more I think they use 3/16?

I will be welding 4AN equivalent JIC fittings to the block-off plates I had lasercut. Thinking of chaining two 1/2 NPT T fittings on the heater port on the coolant crossover, both with 1/2 to JIC adapters on top. I think that will look cleaner then having one T fitting and a T or Y on top.

I might invest in a Fluke 62 infrared thermometer. If I do I'll share my results here.
 
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