overheating under load

[BlazerLT]

This sounds like:

1.) Poor Water Pump not pumping enough flow.
2.) Rad fan not pushing enough air or not set up properly to come on and stay on at tose temperatures. It shouls stay during those hot times.
3.) Coolant mixture is too weak.

[89k5]

The shroud is against the radiator as stock, the electric fan is mounted to the radiator and the blades are about 1.5" from the fins. I have driven the road numerous times both before the mods and after with no problems. The temp never got above about 190-200.

[BlazerLT]

Have you even checked anything liek the rad cap yet?

[Rick Norwood]

So this is not an every time occurrance. You have made it up this hill/road without boiling over before, correct? Are you using Dex-cool or the green antifreeze? You might check to see if your thermostat isn't stuck partially open/closed.

[slammed s10 87]

Originally Posted by Rick Norwood

So this is not an every time occurrance. You have made it up this hill/road without boiling over before, correct? Are you using Dex-cool or the green antifreeze? You might check to see if your thermostat isn't stuck partially open/closed.

check the thermostat?-lee

[89k5]

I checked and reset the base timing, somehow it was advanced 20 degrees!!! I have'nt had the chance yet to try the hills, but maybe that was the problem, I HOPE! I plan on trying it this weekend and will see how it goes, then let you know the outcome. Thanks for all the input; MIKE.

[BlazerLT]

Wow, wasn't it pinging and detonating before?

[89k5]

Belive it or not, no, I don't know how or why yet. But it ran lean according to the plugs, as you said in the other thread.

[BlazerLT]

Advancing the timing leans the combustion.

You had to have been hearing some pinging and detonation.

[Butch Dennis]

Originally Posted by 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.

You state you went to an electric fan and then reinstalled the fan shroud. Did you mount the electric fan right against the radiator with the speed clips or brackets and then put the shroud over it? Or did you possibly mount the fan at the exit/opening of the shroud? Does the electric fan have any type of shroud with it from the factory?

If the timing reset does not correct your predicament, look at the electric fan/shroud combo. It could be the shroud is blocking the cooling airflow at slow speeds. I don't recall seeing where you mentioned if this problem came anywhere near when the electric fan install occured.

I did see a post about coolant mixture mentioned. Hopefully, you are not running anymore than a 60% antifreeze mix to water. This can cause many problems including raising the freezing point and lowering the boiling point of the mix. This information used to be marked on the antifreeze bottles years ago. Most don't remember that water alone is a better conductor of heat than the mix. All the additives like corrosion inhibitors and water pump lube are part of the antifreeze solution and are vital to todays engines.

I have seen an engine that someone ran 100% antifreeze in and the gelatinlike mixture that resulted was horrible. The owner thought that if a little was good, a lot was better.

[BlazerLT]

As he said before, he had this exact same setup and it ran fine.

Advanced timing does lean the combustion fuel mixture and does lead to higher combustion temperatures which leads to higher coolant temperatures.

That is why people that advance their timing use cooler burning higher octane gas to lower the combustion temps down to stop pinging an detonation.

[89k5]

Well, it's fixed! I took it up into the hills this weekend, and the engine did not overheat. I am guessing the hold down for the distributor somehow loosened and it moved. I can't see how else it could end up so far out. I plan on checking it again later this week and see if it moved, but it's good and tight now. Thanks again for all the input, and I hope this may help someone else out.

[BlazerLT]

Thats for getting back to us about this.

Food for thought for the next guy.