overheating under load

[89k5]

Have 89 k5, 350 TBI, 700R4, Overheating when going up local logging roads. Not showing any codes, runs all day in traffic with no problem. I have Flowkooler water pump, griffin aluminum radiator, accel ignition box, Holley throttle body, 8mm wires, new plugs, new cap, new hoses, new plugs, cleanable air filter, underhood welder, Kilby aircompressor in place of a/c pump, and am unable to use my baby for what I engineered her for? Timing is adjusted for new ignition per specs. Now what do I do? Could it be the head gasket? Block, body, and some of the frame is stock, ALL else modified. Problem started recently, after mods it ran great for about 6 months, now broken!

[Rick Norwood]

Assuming that your cooling system is clean and full of coolant, is the new radiator large enough for the truck?

Do you have an external Tranny cooler?

When you installed the new Radiator, did you put the Fan Shroud back on?

Does the forward edge of the fan blades just reach under the lip of the fan shroud?

What about the fan clutch, do you see any evidence of oil leaks or looseness/wobble in it?

[BlazerLT]

Originally Posted by 89k5

Have 89 k5, 350 TBI, 700R4, Overheating when going up local logging roads. Not showing any codes, runs all day in traffic with no problem. I have Flowkooler water pump, griffin aluminum radiator, accel ignition box, Holley throttle body, 8mm wires, new plugs, new cap, new hoses, new plugs, cleanable air filter, underhood welder, Kilby aircompressor in place of a/c pump, and am unable to use my baby for what I engineered her for? Timing is adjusted for new ignition per specs. Now what do I do? Could it be the head gasket? Block, body, and some of the frame is stock, ALL else modified. Problem started recently, after mods it ran great for about 6 months, now broken!

New rad cap lately?

[89k5]

Thanks for reply Rick Norwood. Yes, the radiator is large enough for the truck. I went to Electric fans for cooling with in cab control, no auto switches to fail, if it warms up flip the switch, they work. I did reinstall the fan shroud as well. The factory tranny cooler is in the side of the factory radiator, I didn't want that. The tranny is now cooled by a stand alone BE COOL two circuit cooler with its own fan, temp. gauge, and in cab control, the second circuit cools the engine oil.

[BlazerLT]

I don't think your electric fan is cutting it then.

It is not putting the volume out.

[RexNfx400]

How about if you keep the RPMs up like have it in manual 2nd or something? Run in 4 low with front unlocked? Theres a tool used to detect exhaust gases in the coolent(works good too)
Maybe too much coolent flow(no t-stat)? or obvious, not enough water flow. Temp gage incorrect? Just a few Ideas...

[Rick Norwood]

How big is the radiator? Is it 3 rows wide? 4 rows? If we are to assume that all of the components are in good working order and that you have no problems with overheating on the street, I have to think that you have either insufficient cooling capacity in the radiator, or like BlazerLT says, your electric fans are not moving enough air through the radiator core under the high temp conditions. Are there higher RPM fans available? How many blades are on the actual fan? 4? 6? 8? Maybe you could replace the fan with one that has more blades. Going back to the Radiator, if it is under capacity, (which I kinda doubt) it's R&R time.

[Mikado14]

First off, all you say is overheating. The more demand for horsepower from any engine, the more heat will be created. You say you are driving up logging roads. Have you done this in the 6 months prior to this problem? Standing in traffic, depending upon the ambient temp and humidity may not be a good comparison.

What is the temp (engine) in traffic?
What is the temp (engine) when you are overheating? Are we talking steam coming out? Are we talking 195 in traffic but it is going to 220 on the logging road?

Could you be a little more specific?

[89k5]

The radiator is two core, however each is 1.5" thick, big as the factory four core. The fan is four blade, 16", with aluminum blades from Summit, flows about 2800 cfm if I remember correctly. The temps are about 150 to 180 in traffic with fan on, over 25 mph don't need the fan. When heading to the hills, all is fine until it gets steep and the load increases. If I don't stop to let it cool at about 210 deg. it WILL boil over. So every mile or two I have to stop. The neat part is I'm not losing coolant! I pressure tested the system and the cap, it will hold pressure, unable to locate any leaks. After I completed the upgrades, it ran beautifully with no overheating problems, for about six months. Then one time going up with a buddy and boom, overheating. At first it wasn't too bad but noticable, just progressively got worse until now I am unable to go up ANY steep, long hills! I tried a new cap just for giggles and no change. I checked the hoses for any soft spots when it was warm, none. I can feel the difference in temp from the input to discharge side of the radiator, and it's substantial, so I know it's doing it's job. My thought are going to a head gasket problem, however it's only under load. So I came here to the Forum for more wisdom and ideas or thoughts. BTW what tool is used to check for coolant in the exhaust?

[BlazerLT]

210 degrees and it will boil over?

You sure you have a right measurement?

If that is true, you need to strengthen you coolant misture to 60/40 and put a new rad cap on rated at 15psi.

[Mikado14]

Water boils at 212 degrees. The purpose of the radiator cap is to raise the temp that the water will boil at. A coolant system is pressurized for that purpose just as a steam boiler is pressurized. You will have super heated water. Super heated water is water that is still liquid above 212 degrees.

Now, if you are boiling over, or almost boiling over at 210, then either you need a new cap, change the mix, as BlazerLT mentioned, or you should be looking for an opening to the atmosphere. You mentioned that there is no loss of coolant.
Have you checked the seat for the cap?
What was the pressure rating of the current cap?
Have you checked your timing?
Do you have anti-collapse springs in your radiator hoses?

With all the mods you have done I would install the anti-collapse springs in the hoses. I have a 1969 Dodge Super Bee with a 383. I changed the hoses once and didn't put the springs in. I learned that one the hard way.

[BlazerLT]

I think the coolant mixture is too light.

[89k5]

The temp will go from 210 on up to the point it boils over if I don't let it cool. I understand the theory of pressure is temperature and the reason for the 16 pound rad. cap on the system. Yes the springs are in the hoses.

[Rick Norwood]

I still think your problem is insufficient air moving through the Radiator. Is there anyway to put a higher capacity fan on the truck? I think 4 blades is too few.

You said you re-installed the shroud, I assume the leading edge of the fan blades is inside the shroud. Correct?

[Mikado14]

Did you ever drive this same road or route before and not have it boil over? or almost?