Installing new Radiator, Best time to do the Flush

Alright, I'm getting ready to install my new radiator for my pickup here in a couple days and am going to do a flush on the system to clean out crap from the old one (15 years of service and finally gave up the ghost).

Question is: Should I do the flush with the old radiator installed? Or should I install the new one then perform the flush?

My thoughts on the latter were that there'd be less getting shaken up with the old radiator out of the system when doing the flush to just get pumped into the engine. I would appreciate any advice.

niether.... flush the system with no radiator at all. you should go ahead and put a new stat in with the new rad. with the thermostat out, stick your garden hose right in there and let her flush.

I was considering getting Prestones flush mix and running that through which is supposed to help remove any build up in the system. Good, bad or ugly? Though I do like the idea of running the hose.

gimme a sec...

its kinda a toss up. here's my opinion (master tech) you cant clean in 15 mins what took 15 years to build up. you put that stuff in and some of it stays in and continues to break up old stuff for the next 10000 miles. it contaminates the new rad and also can cause leaks from things like a freeze plug thats rusted from the inside out by disturbing rust and build up thats actually keeping that old system sealed. if youve even done a little maintenance on your cooling system over the years, there is really no need for a chemical.

Wish I could say I owned the truck for the 15 years, I bought it with 83,000 miles on it in 2003 from the state out of its fleet. Its performed faithfully until a couple weeks ago when the radiator finally said "Enough" and stopped cooling as effectively as it used to.

Thermo's current 2 weeks old and the water neck and it should come off without too much trouble as when it was installed the second time (Read my Overheating thread) I only RVT'ed hte side facing the water neck so I could unbolt it again if needed without having to reclean the mounting area on the intake manifold. If the gasket and what not leaks after this is done, its not hard to replace it then. I'll stick with the hose idea, you do make a good point. Just need to remember to put a bucket under the water pump outlet when I stick the hose in so I don't get the mess everywhere.

i think i read your other thread and i remember thinking, from what you described that you may have a head gasket problem but i didnt have enough info to reply to that effect. i need to go back and read it again.

Wouldn't a failing head gasket been seen with signs of oil consumption and white smoke from the exhaust usually? I could and probably am entirely wrong on this.

youre right and wrong. i read back over your thread. it sounds like a small head gasket leak. in most cases youre right, coolant passes through the break in the gasket into the combustion chamber, mixing with fuel and exiting the exhaust giving you the white smoke. in your case, i believe just the oposite is happening. compression is leaking into the cooling system. extremely hot exhaust gasses and pressure are entering into the cooling system. this is causing the gradual and inconsistant overheating condition. the rad isnt a bad guess but it doesnt seem to fit the symptoms the youre discribing. the best way to check for this is a chemical test where you suck gasses out of the radiator into a tool designed for this where those gasses mix with another chemical causing a color change to determine if exhaust gasses are present. this test is pretty acurate.

What's this tool called? I'll see if our shucks here in town has one for rent. The temperature now is only doing the gradual increase and only when it stays at constant speeds, any start and stop and it stays cool. Most likely if it is suffering from the leak because of the fact that there isn't as much exhaust gas being produced. Mind you I've also redriven the same trip and its temp has gotten nowhere as far up as it had that one evening, even with the speed up another 5 mph.

Begining to wonder if some of the oddness is because its running almost entirely water maybe 10-15% of the original coolant mix remains.

believe it or not, ive always known it as a "head gasket chemical tester" if it has another name i dont know of it. i wouldn't expect it to be at your local parts house. the chem is pretty expensive. it is a simple and quick procedure and may be worth your while to pay 30 to 50 bucks for this test.
question... is the cooling system pushing coolant into the overflow tank before it actually overheats. if you run you engine at about 2500rmp sitting still and look for the overflow tank to start filling b4 the engine even starts overheating this may confirm my theory. the pressure cap relieves the pressure in the system usually caused by the coolant reaching its boiling point. if the pressure in the system is above 10-14 lbs without the coolant boiling, the pressure is coming from somewhere.

No change, went out got her up to normal and then wedged the accelerator down so that she would be up at the higher rpm. No change in either the engine running temp or the water level in the overflow tank. When it was gradually warming up it was running for almost an hour at 60 mph by the time it reached half way up from Cold on the temp guage that day and when I repeated the drive yesterday it only got to maybe a 1/3 of the way up from cold.

im sticking to my guns on this one. it sounds more like a head gasket than a radiator. my suggestion is to A: get the chem test done or B: go with the cheaper repair..throw the rad in and see if it fixes it. like i said before, it's not a bad guess.

send me an e-mail when its all said and done. i'd be interested to know what you come up with.

I appreciate the advice Hazzmatt, the radiator's crustier than hell on the inside when its visible and needs replacing before it springs a leak in any case so its good preventative maintanence. I am also pondering just replacing the clutch in the fan as well and having everything I can think of in the main system done at that point.

Prior to me fiddling with the thermostat the first time she had made this run and others in much hotter weather and pulling a trailer up a 6.5% grade without moving an inch in the heat area.

It could be that the gasket may have gone out since then as well.

If all the cooling fixes do nothing then we shall be in a boat of new problems and none that I will look forward to.

P.S. On fan clutches, which is better, the ones that use a thermostat in them or the non-thermal?

Oh one other odd question? If the gasket had gone with a small compression leak wouldn't also there be a sign of it in the vehicles fuel economy? These days the beasts getting 14.8 mpg which is a bit better than what she was rated for on the lot. About a .8 mpg improvement.

ther is benefits to both but i wouldn't be to concerned with replacing it. they rarely go bad anymore. that was the old days. those things seem to last forever anymore. if you do do it, just go with the standard replacement. the one on it has given you good service. there would be no reason to deviate from the original equipment.

And the other question?

only if it was leaking coolant into the combustion chamber causing that cylinder to miss, would it give you a fuel economy change and it would be for the worse not better. this will sound really strange and i cant figure it out but i have seen several engines run there best right before they blow up. i never could explain that but i've seen it more than once. good luck

Hmm... well let's hope its not going to do that, just paid this bugger off don't need yet another car payment to deal with. My last Chrysler product was running strong at 194,000 miles when the vehicle was totaled in a car accident, here's to hoping this one last least as long.