Cooling Question

[Longhorn Man]

I have a mechanical guage run to the same location, and it does not read that hot...headers too.
I am starting to wonder about the pump too.

[67Fleetsidedream]

I have always said it is the RPMs that these trucks cruise at while on the highway.
These trucks were engineered and made in the era of when the speed limit was 55 mph. So with todays higher speed limits, these trucks have higher highway cruising RPMs. You can try a electric fan, flex fan, clutch fan, new radiator and water pump to lower the temp, but until you lower the highway cruising RPMs, your truck will always get hotter than normal.
Try this, On a hot day, let your truck warmed up to normal temp, then drive 55 mph for 5-6 miles and see if it gets hot. Turn around and take the same road back but at 65-70 mph. Take notes to when it gets hot and at what RPMs and speed.
To correct the problem get a overdrive tranny or higher geared rearend. I have a 160 thermo and the same tranny and rearend as you but with heat, A/C and a clutch fan. Mine does the exact same thing at 65-70, but at 55 mph it will never touch 190.
Ben

[crazy longhorn]

At 70 mph,on a 3.73 gear, you should be turning roughly 3200-3300 rpms (depending on tire size)........Your truck should be able to cruise at that speed/rpm all day long without overheating. I also agree with longhornmail, at that speed you should have all the airflow that you need(provided that nothing is blocking the radiator). To look back at what has been changed, it looks like the thermostat, fan, & radiator,& also the trans. When you swapped to the 350 t, did you run the trans lines through the rad,or install a add on cooler? If you dont find a problem with coolant flow, you could be just a couple degrees off on the timing,or a little lean on the carb.......good luck.....Al

[67Fleetsidedream]

I thought the post was about the engine getting unusually hot. Not overheating. My truck has never overheated.
Ben

[crazy longhorn]

I can rephrase from overheat,to unusaully hot,but it still shouldnt be a problem cruisin @ 70mph if the system is in good shape. I run 4.10 gears on a 28" tire. that puts my 60 mph cruise @ 3000-3200,& i hold @ 185 on the temp. i can turn it up to 4000 rpms & cruise @ 80 mph with the truckers,& will only see a 5 degree increase in temp after 10mi of runnin that speed /rpm. with a 195 stat, Im still runnin where Im posta be. with most of the old trucks I have had, i have seen more trouble with them running "warm " in town, when the airflow/pump speed is low. In stop/go traffic, I run @ 200 degrees,but dont see that as a problem......still close to the stat rating, & pushin 400hp to boot. I do however run a 4 row core radiator that is fresh.....Al

[Ed ke6bnl]

I can only speak from experieices I have had this happen more then one time. And that is I have gotten thermostats that are bad from the near get go. We just pulled the stat and took the guts out and reinstalled the restrictors in my boys truck that normally runs ice cold that not long after getting a new stat started to act up even started to creep up at freeway speeds. The truck is now running cool. We plan to replace the defective stat.

Prior to this we had to extend the fan shroud so that about 1/2 the fan blade is with in the shroud. we have also found that it helps to seal all areas between the shroud and the radiator so the air that is drawn in is only the air passing through the radiator. Good luck and make sure you have a lower radiator with a spring in it I know Napa sell them. So it does not colapse at higher speed lot of luck Ed ke6bnl

[Longhorn Man]

67Fleetsidedream, the double nickle speed limit was not in effect untill 74 if i am not mistaken, it was set by the feds to help conserve fuel. Before that, it was up to the individual state.
So in essence, they were designed to run at about the speed most states post...70-ish. (except the faggot Ohio lawmakers who think 65 is a good speed)

[hanssolo]

My Gosh! Great stuff here. Let me get in on this.
1)External trannie cooler. How does cooling trannie fluid thru almost boiling radiator water cool off? They both combat each other.
2) Use a flex fan with an electric back-up fan. Connect it thru a relay that goes to a coolant switch and the A/C cycle switch. I put it between the radiator and the condensor.
3)Good fitting fan shrouds very important for stop and go traffic.
Overheating at freeway speeds could be carb. jets one size too small. Also ign. timing may be too much cause its running fully advanced for a long period of time.

[ThreeQuarter]

Yeah, longhorn, I think our trucks are geared this way because they were built to work. I can imagine the GM truck engineers in 1966...I can see it now: "A freeway? That's what Buicks are for!" LOL

[crazy longhorn]

I bet those 4.57 gears keep that327 hummin on the free way! My longhorns work days are over,shes all on 1/2 ton parts(12 bolt posi/4.10 richmonds)....... shell still take that "Buick" to about 126mph tho.......tachin about 6400

[Sinister]

i heard a good way to check a new thermostat is to toss it in boiling water, should open right up...
about freeway rpm, i've run 24 hours at a ton +, from san antonio, texas to tampa, florida, only stopping for gas and to check the oil, no problems with temp.
running 3.73 gears, stock fan, shroud, 180 degree thermostat, 3 core radiator for a caprice, (fits perfectly), i had to pick it up in universal city, texas cause my POS radiator had ate it...

[Stano]

Bout forgot the tranny cooler. Its external mounted. Put in 192d thermostat and it stabilized a little. Runs about 200d to and around town and gets up around 210d+ on highway. Pulled off hoses and checked them. OK. Think I will put in a 180d stat and new water pump this weekend. This is getting old, fast!

It also never turned over 2800 with 3:73's with 275/60's. Now its got 285/65's (I think) pretty tall and wide. Kinda tubbed look at a glance. And never ran over 195d with a 22ft camper in tow before.

Thing about it is I have spent so much money gettin this thing legal and all I am tired of spending cash for a while. And when I do it isn't helping the cooling issue. GRRRRR!. I have a nice thermostat collection though. LOL

Gonna go try something and it won't cost a dime. I'll be back later.

[REPO1]

Yes, please post reply if you find a problem. This is a good learning experience for us all.

You mentioned that alot of the parts are off of other vehicles, if so, what it the pump from? Is it turning the right way?

(I.E. a pump from a serpentine system is supposed to turn in reverse to a pump from a V-belt system)

[Stano]

Well that wasn't it. I couldn't remember if I had my advance hooked to full or timed vacume but it was hooked to timed. And I noticed after a quick drive that when I got home my water neck is pissin a little. If it ain't one thing its another. Oh well I was gonna take it off again anyhow to put in a 180d stat.

[Stano]

Repo, The radiator is new, as is fan clutch a sack full of thermostats, water pump was used about a year before it was pulled off and stored, hoses too, new shroud(thanks Mudder67), Heck its all been apart so many times nothin is new anymore. Threads in the intake for the stat housing have more miles on em than the truck has had put on it so far.

And when these trucks were built the speed limit was 70mph in most places. Around here any way I am told.

[Stano]

I replaced my water pump. Looked in the old one and it looked brand new inside impeller was shiny and all. I put in a 180d stat, new flex fan(shut up lol), and I put a smaller pulley on the water pump. It now runs 190d and 200d hiway. Thats good enough. I am tired of friggin with it. I made me a heat shield for my starter out of aluminum. All the parts stores around here had some little pos for the solenoid. Looked like a metal condom. LOL about $9. The one I made was free and it covers the whole side of the starter and solenoid, looks and works good too.

[REPO1]

Glad to hear its driveable now anyway.


You should try a bottle of "Water Wetter" just to see if it helps any. I use it in my Z28 and it seems to run very cool.