whats the right temp range

I got a 77 g10 with the straight inline 6 and factory carbonated set up. I own a few older vehicles and cannot remember if I replaced the thermostat or not in this van but I did a radiator flush with that radiator inside cleaning product stuff, because the heater was not too hot in the winter. After the flush the heater works fine. There is an aftermarket temp gauge previously installed in the van by previous owner.

Anyway I'm about to take a trip to New Mexico and its still summer so I want to double check on if my cooling system is behaving normal for this engine.  Right now its been in the mid 90's in Colorado and when cruising around on flat ground at say 30-40 mph without traffic lights or going sown hill the temp gauge is usually at about 185-190. so if Im not pushing the van and coasting around in an easy fashion it usually is about 190-197 degrees. but it will creep higher if I drive with any stop and go or enthusiasm.

If I driving a little more aggressively and in stop and go traffic. then the temp is usually 200. It will hover there. Also 200 is where it will go to if I just leave the truck idling in my driveway without moving. It will be at 200 a bit over 200 if it is a hot day outside. But what concerns me is the highway driving temps in the summertime.

at HWY speeds if Im trying to accelerate and pushing to gain speed to 70 and over and especially when going up hill it will get to 205 and 210. maybe even 212. after it reaches any temp over 200 it does not get below 200 unless i intentionally coast without a lot of gas at slower speed especially go down a big hill. then maybe it might get back to 190. so usually it hovers and changes between 200 and 205 and sometimes 200 and 210 depending how im driving.

When I shut off the truck the gauge will climb higher sitting without the water pump going. sometimes up to 220. when I turn the car back on it will slowly go back down to 205

does this seem normal or is it running a little hot? should i throw in a 180 thermostat? or add after market electric fans?

So lets start with how old is the radiator,,,,, when you drained the coolant,,,,,was it muddy,,,,,,,when you look down in the radiator, can you see if the tubes are clogged,,,,,dirty heater core sure can mean dirty radiator,,,,is it a down or crossflow radiator,,,,,,,what temp thermostat is in it,,,,,,,,when its hot, can you feel cold spots anywhere on the fins,,,,,,,,do you have a shroud on the radiator?

Thanks donivan65. Its a cross flow radiator. No shroud. I do not know what temp thermostat is in it because it was a very busy time back when i did the flush I assume I installed a thermostat it when I did the flush. If I did it is either 180 or 195. prob 195 because I did the flush because i was not getting a lot of heat from the heater in the winter so I think I would have put in a 195. and I also tend to research and put in the OME type. So i think that is 195 but i do not remember exactly.

I do not think the fluid stood out to me back then as especially thick, but I think I remember it was not green and looked like brownish tan or like if different colors were mixed in it from the prior owner. Right now its been a year since the flush and it is i think a normal green. When I did the flush i did do it a few times with a garden hose and then filled it with distilled water and the green type coolant.

The radiator feel test. Just now I ran the van 25 minutes until hot and got it to the point its idling at 195 parked, but it is actually a very cool rainy day. the upper driver size area feels hottest (closest to the inlet hose from the engine) . the middle level driver side area feels hot but not as hot. the mid-lower feels warm but bottom driver side for like 3 or 4 inches up from bottom feels cold and I can see through the gate that there is a cross flow tube at that level, which probably is clogged. In middle section of radiator i feel the most air pass through from the fan the lower section is also cold and the mid lower is slighlty warm and the top is slighly warmer. On the passenger side the lower is cold, mid is cold and upper is slightly warm. it is a cooler day. The lower cool and hose feels slightly warm to the touch. I think the cool air today is really cooling down the coolant well and of course the van is just sitting idling so not generating as much heat as on the highway.

I turn the engine off and a few minutes later the top is very hot and middle level is warm on the drivers side and in the middle, the lower driver side is a bit warm but lower central part of the radiator is cold and the lower passenger side is cold.

I assume therefore it is the radiator having clogged lower cross tubes. Let me know if you think this is right as your test suggestion seems to point this out.

I do remember the temperature being less fluctuating right after I did the flush a year ago, so maybe it was freed up a bit back then, but I think I did it still in colder weather when i did that so maybe i was seeing the problem even in the winter back then. It was a busy time so i do not remember exactly.

So now in hotest summer weather on hwy it still shows not full radiator capacity if coolant is not flowing through the full radiator the the lower cross pipes. Maybe since the last flush more debis came out of the heater and got stuck in radiator or that flush did not get out the debris from the lower pipes

thanks

That 195 thermostat,,,,,,,helps ,,,,,,,,keeping you warm in he Winter,,,,,,but it stops any hot coolant from leaving the engine until the coolant gets above 195,,,,,,,try a 160 in there and see if you notice any change,,,,,,,

Yes I will switch the thermostat especially for this trip because i will be in the south east desert, but does anyone have experience with radiator flush products?. I used the prestone stuff last time so I think that did not do it for me. Some forums say to use vinegar and other say CLR cleaner. any thoughts appreciated. the most convincing idea I see is pasted below but a simple product might be easier before I try the the below:

"Professional cooling system de-scaling is done with Sulphamic acid for hard water, lime and antifreeze build up. Oxalic acid is used to remove rust.
Sulphamic acid crystals are available at the hardware store in form of 'grout and tile cleaner'.
Oxalic acid crystals are available in form of 'wood bleach'.
Containers say what acid is used and its pure acid cystals with no other additives.
Available in 16oz. containers, which gives the right mixing ratio with water for the typical car cooling system with 3-4 gallons capacity.

Properly diluted, both acids are just as mild and safe as vinegar (acetic acid) and citric acid, but are more effective and cost is the same.
These treatments are safe to use with copper/brass radiators.
It is supposed to be safe with aluminum radiators as well, but I would do some tests first to determine how much reaction time is actually safe.

Oxalic acid used to be sold as a heavy duty 2-part cooling system cleaner over the counter until a few years ago. Recommendation said to do this annually...

For best results it's essential to keep temperature at engine operating temp and to keep the flow going.
Instructions are to drain and flush first, then fill with the diluted acid mix and run the engine at fast idle for 3 hours.
Do one acid treatment at a time, starting with the sulphamic acid, then drain and flush, followed by oxalic acid, then drain and flush.
The final step is to neutralize any remaining acid with a mix of washing soda and water and run the engine again for a while, then drain and flush and finally fill with coolant, but using distilled water instead of tap water, this time."

So how many rows of tubes do you have in that radiator,,,,,A/C, stick or automatic?

,,,,,these RockAuto Chevy Van radiators look,,,,,,,,,,awfully,,,,,,,,,,,,interesting......

Thanks for this question and line of thinking. no AC, 3 speed stick, its a g10 so its a 1/2 ton van, not heavy duty. and its a inline 4.1L 6 Cyl .

I never thought of how radiators are constructed. I just watched this video https://www.youtube.com/watch?v=A65613TaWYw and this guy cuts open a radiator, this is very helpful to actually see what 3 or 4 core means.

I do believe from web research most the of radiators for these vans were 3 core radiators.
I imagine since i just have the 1/2 ton and the smallest engine for these vans, its radiator is not the highest capacity and I figure maybe trying to see what capacity the system is by how much coolant it takes. When I research on line amount of coolant a 77 g10 will hold, i cannot find specs for that old a year, but I do see in 1995 the have listed different amount of coolant with different size engines, so they probably had different radiator capacities (in 95 the 4.3L engine takes 4.5 quarts, the 5.0 and 5.7 take 5 quarts, and the larger 6.4 and 7.0 engines take 7 quarts). So in 77 they also probably had different capacity radiators.

In my book, when you use a cooling system cleaner, it just loosens up all the junk in the engine and the water pump pushes it into those small tubes that run through the radiator,,,,,and makes it worst,,,,you should go to a radiator shop, and see if they can,,,,,boil out the radiator or  by properly,,,,,,,disassembling,,,,,,,the tanks and running a rod through the tubes,,,,,the radiator has to come out for this,,,,this way you dont have to worry about if a new radiator will fit, have the correct hose fittings or any capacity concerns,,,,,,  so check that out,,,,,

I think since the 77 is in the third gen, there are plenty of aftermarket radiators that can fit for a low price. I will try to CLR flush. what some people on you tube (who say they had success in classic cars) if it does not work then i will get a new radiator.

But actually I realize I never got a answer to my initial question. I say above sometimes it gets to 205 or 210 degrees on the hwy with a 195 thermostat installed. I still wonder, maybe this is not to bad in the first place? The only reason I am concerned is because how it looks on the gauge, more than half way. what is normal operating temp range for these engines? does anyone know?  

So what Im going to try is

1. plush radiator system with water a few times until it is clear and free of all coolant.

2. Add in a bottle of CLR   Calcium Lime Remover... which is pretty strong stuff, sttoger than any auto radiator cleaner.  And then after that bottle of CLR Add a few gallons of vinegar, because vinegar is also a cleaner and has a boiling point of 244 degrees.

3. Run the car with that stuff in it for like 3 days.

4. Drain out and flush the system again until it is clean. and also do the last flush with distilled water and add some dissolved washing soda in the last flush to neutralize any left over acid.

5. then flush it one more time.

6. then add the coolant with distilled water.


So im listing the steps so if it works people know what I did.

I will report back and let you all know if it helped or if I need a new radiator.

How accurate is that gauge,,,,,a themo radiator cap or an infrared gun will tell you what the coolant is,,,,,other things that cause an engine to run hot are wrong timing or bad vacuum or centrifugal advance units in the distributor,,,,,,and then of course is the sniff test that determines if the head gasket is leaking,,,,,,,but I would say under 212 is where you want to be,,,,,,it will go higher going up hills,,,,,as well as when you shut off the engine,,,,it might even puke into the overflow tank,,,,

I did the CLR flush with the 6 steps I listed above. It worked and solved the problem. the issue was clogged radiator and the acid in the CLR flush worked. It was very interesting.  I first took out the thermostat *it is a 195). The CLR and Vinegar (I added no water) bubbled when I put in in. It was producing gas. I added vinegar to the overflow tank as well because it was hard to know I filled it up all the way. I drove the van on the hwy and to town and let it idle. I could feel the radiator was hot where it was not hot before. I drove for about 2 hours. let it sit overnight.

When i felt the upper hose in the morning totally cold engine did not run it at all, it was still pressurized since yesterday, so the gases released from the acids in the engine also ended up giving me a pressure test, so I have no leaks in the system.  When I took off the radiator cap, engine still cold, I really hear and see the pressure release and more foamy bubbles. Then I did all the steps. and a whole lot of flushing with garden hose. a lot of brown rust like water came out.I ran the engine a few times in this process.

When i did the last flush with about 3/4 cup of washing soda powder dissolved in, also running the engine with that in there, the water turned blue. that was really cool. then I again flushed it a number of times, and the blue turned into more slightly brown. Then It was eventually clear.  I  replaced the thermostat before adding distilled water and green coolant.

I bought a burping funnel kit. and the van already had an inlet for a hose to connect to the heater inlet.  used a female to female washing machine hose to make that work. So about half of my flushes were done this way without a big mess of spilling water and easy to collect in a 10 gallon bucket. but I also totally emptied the system from the bottom into a collection pan as well, and of course this did during the very last flush before adding distilled water and coolant into a totally empty radiator. and burped out all the air.  This burping kit also helped because it made it possible for me to connect a hose out of the top of the radiator from the cap opening, even thought this is not the intention of that kit.

These are the products I used.

OEM TOOLS 87009 No-Spill Coolant Funnel Kit, Near Universal Fitment, Translucent, 15 Piece Set $19.99

https://smile.amazon.com/gp/product/B01A2CQSU6/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

and the van already had the stuff from this kit in it.
Prestone AF-KIT Flush 'N Fill Kit    3.79 at Walmart nearby also on amazon

https://smile.amazon.com/Prestone-AF-KIT-Flush-Fill-Kit/dp/B000CCFY5W/ref=sr_1_3?dchild=1&keywords=radiator+flush+kit&qid=1599171961&s=automotive&sr=1-3

CLR Calcium & Lime and Rust Remover 28 OZ 5.99
https://www.homedepot.com/p/CLR-28-oz-Calcium-Lime-and-Rust-Remover-CL-12/100049980

So this solved the problem. I still think I will install a 180 thermostat before heading on desert highways

Thanks for all your help and hope these steps help others.

Cool, please let us know how the trip goes...Best of luck on your trip and stay safe!