View Full Version : \\\'86 Chevy K30 454 Runs Hot

03-11-2001, 12:01 PM
My '86 carburated K-30 with a 454 & Turbo 400 still runs at 230 degrees at 70 MPH even after a new 4 row radiator, 160 degree thermostat and 17" flex fan. During City driving the engine runs pretty warm also. The Carb was recently rebuilt by a competent shop and timing is at 4 degrees advanced (a little low) mostly to compensate for the oxygenated fuel in Los Angeles. I was thinking the stock water pump might be the culprit, but unless it leaks, there isn't much that could go wrong with it. That may be my next step along with bypassing the interal cooler for the trans and just running the external one. I'm curious whether anyone has had this problem and what they have done to solve it. Any suggestions would be appreciated.

John DiMartino
03-11-2001, 12:44 PM
A high flow water pump might help you.The 17" fan is small isnt it?I had an 18 on mine that 1" will make a big difference in airflow,especially at idle.Another thing you can do is pinch off the heater core lines in the summer when your not using it,I dont think you have a hot water control valve-but by closing off water flow to the core-you are forcing more water thru that new 4 row radaitor,where it will do the most good.Another thing you didnt mention and is very important,is the antifreeze mixture.Is it 50/50% or stronger?If your in a warmer climate,keep the mix very weak,(lots of water,sindce water transfers heat better)and run Redlines water wetter additive its about 7 bucks a bottle,but it really works,it helps the transfer of heat from engine to radiator.I used it on my Iroc,it ran hot when cruising,it dropped temps a good 10 dergrees.The water wetter also contains the additive pgk to prevent corrosiom in your cooling system,so ruuning little antifreeze is OK,with water wetter,it wont rust up your cooling system.Good luck

03-12-2001, 10:27 AM
Keep in mind that while traveling @ 70mph your fan is no longer helping draw air through the radiator. What are you running for coolant? If you have too much antifreeze mixed with water it will run hot. Is your radiator cap holding pressure good? If your carb is running lean it could make you a little hot.

03-12-2001, 01:27 PM
When you replaced the radiator and thermostat you did not mention that you replaced the radiator hoses. Some times these items can seem fine sitting still at idle or even while driving around town but under constant acceleration they sometimes can suck themselves closed.


03-12-2001, 11:39 PM
John, BigUgly and Bruce - Thanks for the suggestions. I've thought about going to an 18" fan but the 17" I have is a large bladed seven blade and it's soooo noisy it seems a larger one would only add to that problem. I may have to sacrifice my hearing or go back to the clutch fan. High volume water pumps are about $80-$100 so I wanted to try the cheaper fixes first. Any ideas what the flow rates of the high volume pumps are? Is the flow higher across the board or is it normal at idle and builds from there?

I've been running about a 70/30 antifreeze/water mix due to the high mineral content of the water here to prevent corrosion. Thought about using distilled water but the motor still has the original steel freeze plugs in it and I've experienced these disintegrating in other vehicles in the past due to what I believe is deionization of the metal due to the lack of minerials in the distilled H20. I've thought about Arrowhead or Sparklets, but haven't given it a try, but I'll decrease the mixture as suggested. I'm going to try power flushing the block too when I can afford to have the truck down a week or two if the drain plugs break off.

Any idea where Redlines Water Wetter Additive is carried? Cap is a new 13 lb Stant. Bypassing the heater core may help but due it's routinely 55-60 degrees here (Los Angeles west coast beach area) summer mornings so that one's a tough decision from a comfort standpoint. The hoses are new but that doesn't mean they don't collapse. The quality of hoses and belts from the local parts places (Kragen, AutoZone and Pep Boys) just doesn't seem to be extremely high - I'll check that to see if there is a problem there. Last time the truck was smogged the mixture seemed to be about where it should be and the plugs look OK.

It's interesting, my son has a 400 CID small block in his '73 Chevy 3/4 Ton that runs extremely cool with the same setup I have and those motors normally run really warm....

Anyone tried and had any luck with an electric fan (or 2) to supplement the mechanical one?

Keep that input coming, I'm sure if I do all this stuff I'll get this licked....


03-12-2001, 11:48 PM
The electric fan always seems to be a big hit with the high performance crowd and they put their mills through as much as any of us. The rad hoses I like for the bottom are the ones with the springs inside to help combat collapse.


03-14-2001, 03:00 PM

Is this an original 454 truck? Go out and get a new clutch fan rated for 180 degree stats and factory fan. They pull huge amounts of air compared to those wimpy flex fans. Drop in a 180 degree stat. If this doesn't work, then something is wrong. Something is making too much heat! Do you have any big "good buddy" lights blocking the grill area? Also, what gears are you running? What rpm's are you turning? These trucks aren't made to run at 70mph plus for extended periods of time. Also, has the waterpump been replaced recently? There are two types (3 really) one for v-belts and one for serpentine belts. Neither will work on the wrong belt. The reason I say to go to a 180 is that the 160 is open too much and with your high speeds, water is circulating too fast and not properly cooling. Hope these things help cool down your hot rat!

03-14-2001, 06:02 PM

I believe you said earlier that you had not changed the water pump yet. Usually you see a trickle of coolant from the "weep" hole in the front of the water pump. I have however run across a situation where I took a water pump off and found that the impeller had come loose from the shaft and there was no indication of this problem outside. No idea how you could check this without taking the darn thing off but if you have to take it off you might look at this.


John DiMartino
03-15-2001, 01:52 AM
I got my redline water wetter from Summit racing.Your 70/30 mix is part of the problem-make it 30/70,add some water wetter and watch your temp drop.Im willing to bet you'll drop 20 degrees peak temp with those changes alone.Water wetter has corrosion protection in it,you can run straight water with it,if you want to -I wouldnt-but you can.As for the radiator hoses,the lower hose is supposed to have a spring in it,to keep it from collapsing ,since the lower is the suction side of the water pump.If it was removed for any reason,and the hose collapses the temp will skyrocket instantly,not the case here.If there is any baffling in front of the radiator support,make sure it is there,.and sealing angainst the radiator at speed,so all air goes thru the radiator,not around it.Good luck