Time for a Radiator Upgrade...?

[7900_Blazer]

You should be totally fine with the stock radiator and setup you have unless you have bumped up the power output a lot or have a BBC in there.

The cheapest and easiest solution would be to take that radiator in to a good local radiator shop and have it fully rebuilt. You also NEED to put an overflow tank on there. The radiator is so plugged that the water pump is pulling all of the coolant out of the side the cap is on and nothing is making it through the radiator to replenish it. That is one of the worst plugged radiators I've ever seen, and that's saying something.

I bet that is why the spacer is on there, the PO was probably having overheating issues and they got rid of the fan clutch to try and help it out.

Here's my recommendation:

1. Go down to the parts store right now and get a bottle of radiator flush and an overflow tank.
2. Pour the flush in, top off the radiator and overflow tank with distilled water and drive it for a few days like that.
3. Drain out all the coolant and flush fresh water through the block until it comes out clean.
4. Take your radiator down to the local shop and have it rebuilt
5. Get a new 195 thermostat
6. Get the right fan clutch and replace the spacer with a fan clutch. The fan you have should be fine.
7. Once everything is replaced, cleaned, and flushed refill with new coolant concentrate and distilled water in a 50/50 mix. NEVER use anything other than distilled water in a coolant system unless it is just for flushing the cleaner out. Those deposits are from someone running tap water in their system for a LONG time.

Also, if the radiator looks like that, I'm sure the heater core is probably just as bad. You might want to look at that while you have the cooling system drained for refreshing.

@Bextreme04
Thanks - super helpful. I found a shop in Dallas (nothing any closer) - so I'll pull it, drive my trusty Dodge Cummins in and get it rebuilt along with getting rid of the spacer, no fan clutch (@AuroraGirl).... etc...

BTW: I went back and read through my 'stranded' thread... and with just a cursory glance, I counted 15 pieces of 'advice'; all of which I did AND reported back on so that whoever happens on that thread in the future can take advantage of them...... so not exactly sure where you are getting your: 'you seem to ignore a lot of solid advice', that was a bit uncalled for, not a big deal though

Again, know that I very much appreciate you all stopping what you are doing and working on these issues... I always learn a ton.

 

[7900_Blazer]

I'll post a picture of the Champion aluminum radiator I bought from Jegs for my '75 GMC K25 in 2018 (after I accidently punched a hole in the copper 3 row radiator). The old copper 3 row radiator worked fine most of the time, but with A/C on it spiked up to about 210+ in slow traffic at idle.

I have the aluminum radiator, a high flow water pump and 195 degree high flow thermostat, and stock steel fan with factory shroud and Hayden severe duty fan clutch. The heater return hose connects to the radiator. My RPO sticker shows that my truck originally had the factory HD cooling option.

In 90-95 degree weather I could start up the truck and turn on the A/C and it will idle for hours and never get above about 190-195. If I run it at 60-65 on the highway and then stop at a light it might spike up to 205 for a very short time as I first stop and it comes back to idle, but then the thermal clutch fan catches up and it goes back down to 195.

I would not recommend using electric fans, since the stock mechanical setup is so trouble-free once you get the right parts installed. However, if you do decide to go with electric I can also give you the Lester number for the 93 amp 12si alternator that could replace your original 10si.

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@75gmck25 Thank you for all the info... much appreciated!

 

[7900_Blazer]

Fix your radiator with a shop, get a new fan blade and clutch and see where it places your blades in relation to the shroud.

Being you just ignored my post on charging system I DEFINITELY don't recommend a electric fan. You also ignored the very real belt dilemma you seem to have which is going to **** your day in either a belt or electric drive fan, so that's nice.

You want help but it seems like you have determined the answer you will accept but are trying to squeeze it out of us.


I can do this all day. Lol.

@AuroraGirl Not at all trying to ignore your expertise... I appreciate your knowledge and help... just prioritizing my list

 

[7900_Blazer]

Also, I don't see the nipple on the radiator for the heater hose return and the trans cooler lines don't have anything running to them. Do you have an auto trans? Does the heater hose return go directly to the water pump?

Heater hose runs... one into the intake.... the other into the water pump.

Currently have an SM465 I purchased off Facebook Marketplace to get me 'down the road' a few months until I can get my '71 running for my 16 year old.... then my goal is to shoehorn in an 4L80E...

 

[7900_Blazer]

I would start with a good flush and see if that gets the radiator to allow the coolant to flow better. I used prestone flush but. Any will work fine. Maybe you'll have to do it twice as yours looks pretty clogged. It's cheap and easy and then go from there.

I'm not a big fan of the flex fan but. I had one on my 75 square in high school and it did work ok for me and didn't overheat.

Flush it then see where you're at. I'm in Texas too so know how hot it gets here. Lol

If that doesn't help maybe call these guys and get them to build you one for your truck.

https://radiatorsupplyhouse.com/?utm_source={{campaign.id}}&utm_medium={{site_source_name}}&utm_campaign={{adset.id}}&utm_content={{ad.id}}

Much appreciated!

 

[80BrownK10]

@Bextreme04

Not ignoring your advise...

Maybe I am.. because I do not think adding a return line is going to lower my engine operating temperature from 220 down to say 180 or 190 - maybe it will though and I'm completely wrong... won't be the first time.

I did ask a specific question that has been ignored - but that's fine...

Still I do appreciate the thorough feedback. I have a 180 degree thermostat that I can put in v.s. the 160 degree one that I took out when it hit 220.

Do you think changing from the 160 to the 180 is the problem?

Thermostats are not your issue. You need one in there but it's not going to make any difference, your getting so hot any t stat is going to be wide open after just a few mins of running time .

 

[80BrownK10]

Some pics

Video at idle: https://youtube.com/shorts/h4IMsrPxSlI?feature=share

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100% your problem is a stopped up radiator. I'd have it rodded out!

 

[Turbo4whl]

You should also have a coolant recovery system on your radiator. When the system warms up the coolant expands. When it cools, it contracts. At this point air is sucked back into the cooling system. The air can and will help the corrosion form.

With the recovery system, expanded coolant in the recovery bottle returns to the radiator instead of air.

Newer term for that overflow bottle is "degas bottle" This is a better name to describe what the system really does.

 

[MikeB]

Just a couple of comments:

My 82 C10 with 350 and no A/C ran a $130-something "Murray" aluminum radiator that I bought at O'Reilly Auto Parts. It's listed for 6-cylinder up through 350 w/o air. Folks on forums laughed at me, but one of the reasons I did it was because a guy on a Chevy truck forum (maybe this one) said he ran the same one with a blown 383 and had no issues. Also, I already had the proper brackets and OE-type fan shroud. It had a 30-day return policy and a lifetime warranty, so nothing to lose on my part! However, if you go this route, get the radiator that's the same size as your current one.

The truck also had a OE-type 7-blade fan with light duty clutch and factory shroud. Water pump was a new AC Delco; t-stat was either 180 or 195.

Even in high-90s low-100s air temps, the setup kept the coolant at around 180-190 and got to only 200 or so at long stop lights. That was for 5 or 6 Texas summers until I sold the truck.

If your overheating is caused by fuel system or exhaust I'd be surprised, unless the mixture is WAY too lean or exhaust is somehow restricted. But I think you'd be getting pre-ignition clatter if either of those was a problem.

Finally, I just noticed the pictures of the radiator internals. Wow! If you few or no pinhole leaks, which is doubtful, try using one of the powered cleaning solutions, if they are still available. I did just that on a 30+ year old radiator, and was amazed at how much crap came out. I did it with radiator in the driveway lying on its back. After two treatments, letting it sit for 10-20 minutes or so each time, water flowed through 2-3 times as fast! And the driveway was covered with white sediment. Awesome stuff!

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[peats]

I bought an aluminum rad from Rock auto for my '81 c10 360/700r4. was amazed by the low price. i run a 160 stat and the truck never wavers off of 170 degrees. Gotta believe that cooler temp is good for the trans. I'd shelve that rad and replace it, less than $150 if i remember correctly

 

[AuroraGirl]

I bought an aluminum rad from Rock auto for my '81 c10 360/700r4. was amazed by the low price. i run a 160 stat and the truck never wavers off of 170 degrees. Gotta believe that cooler temp is good for the trans. I'd shelve that rad and replace it, less than $150 if i remember correctly

that temp is low if you dont have some extenuating reason for it, like --
wait
360 is a small big block right? nvm

for a big block that is proper

FOr a small block, that would be cold

if you were worried about 700r4 temps, a auxillary trans cooler piped after your radiator end take cooler would be a good addition.

 

[MikeB]

I bought an aluminum rad from Rock auto for my '81 c10 360/700r4. was amazed by the low price. i run a 160 stat and the truck never wavers off of 170 degrees. Gotta believe that cooler temp is good for the trans. I'd shelve that rad and replace it, less than $150 if i remember correctly

Here's a link the RockAuto radiators for 75 C10. Probably the same as the one I had in my 82.
https://www.rockauto.com/en/catalog...50cid+v8,1030093,cooling+system,radiator,2172

 

[peats]

.60 over 350. running this combo for 21/2 years now. I didn't put the 160 in for the trans specifically. one of the best running small blocks i've ever had. Tell me why you think this is too cold even though i have no intention of changing it.

 

[AuroraGirl]

well unless you have a high compression ratio esp compared to stock for the year, the engines are lower compression in general and they run cooler to begin with. if its not smogged, if it has headers, etc, it wont be holding a lot of heat in the engine. and at 160 you are slightly below the optimium temperature for combustion chamber, potentially, and that is more dependent on your heat range of plug and if you hae forced induction often times, and of course, timing over all. i dont know your setup obviously, but if its, for example, a bored over 350 with no smog components and maybe just external HP gains maybe getting it near 300, maybe sub, with the factory heat range plug and stock timing spec, maybe you run manifolds or maybe not, you could be below optimum temp. Power isnt gonna be like suffered suffered, but unless you drive rather exclusively a good 30+ min a day, you may be keeping the crank case cool enough and not dried out. when cool they condense moisture and then you get creamy oil. Hotter temps, closer to the boil point, dont need as long to evaporate the water in the oil. but short trips will negate that idea almost no matter what


but, say, you are pushing some ponies and maybe have some high compression heads or you run 91 etc because it would ping otherwise, or maybe you have a turbo etc etc, you very well may need that 160 t stat to keep your combustion chamber the right temp. i dont know your truck tho

basically its not like your killing anything, but if you were a stock situation you could potentially make more efficient cleanliness of your crankcase and also with the right plugs keep them from fouling. I forgot to mention that, having the wrong heat range or significantly lower temps around in there could make your plugs foul more.


should have saw how milkshake I got my park avenues crank case when I ran without a t stat for a couple days and it was a cool, foggy evening and it was hot the time I parked. Took a while to get it not milkshake, but it was a no-stat scenario vs a lower. If i use a 180(lower my car calls for) in winter and dont block the radiatiro, the car struggles to break 150, 160 in driving scenarios. In city it will eventually get 180 but that temp stuff is significant to the PCM for torque converter lockup, but thats a electronioc controlled transaxle, i doubt you have that worry in your truck

 

[73cheyenne]

Looking at your pictures, the radiator is obviously plugged. By the time a radiator is that old, it's corroded junk. Just put a new one in and be done. If you waste your money trying to clean it, it will probably leak.

The radiator in my '73 was plugged and leaking. I put a new 4 core in it. No use messing around trying to fix junk.