any auto mechs here?

Doing some engine work that involves letting the engine idle for an hour before draining the radiator and block.
Did that OK, but when the petcock at the radiator bottom was opened, the water that came out was cold. Should have been scalding but wasn't.
What or where could it be getting blocked from circulsting like it should?
I know the pump is good, so what caused this?

 

Have you checked the thermostat?

 

None installed.
I removed it several months ago.

 

I'm not a mechanic but seems to me that if the water was not circulating, the temperature gauge on the instrument panel should have gone way up.

 

How old is the radiator?

I've found over the years that flushing can be useless, especially with age or if it's a GM product that used the original Dex-Cool formula. The first formula would gum up everything because it would "gel".

I had a friend of mine whose '99 Blazer would repeatedly lose heat, and I must have hooked up a hose to the heater core over a dozen times one winter. Mainly because it was easier than swapping the core, and he got rid of it the following spring anyway.

 

That MAY be why. The thermostat is supposed to be closed until the engine block warms up, then open to the radiator when warm. If there isn't any there, the radiator is going to be cold for a lot longer.

 

Original radiator in a 2002 Nissan Sentra.
16 valve,twin cam 4 cyl.
Temp. gauge is defective.
Water was boiling hot in the top of the radiator, but cold as ice at the drain plug.
Always been my experience that the water at the plug was as hot as what was at the top.
Something just isn't right.

 

Phantom.
No way should it be that cold after running for over 1 -1 1/2 hours.
Even without the thermostat.
Was removed because of overheating.
Now trying to find the cause.

 

Yer right, an hr+ of running time should get everything hot. Must be blocked somewhere, (unless it's the water pump - but you said that's good). Done an engine block and radiator flush, yet?

 

Really sounds like a plugged radiator. Ten years from an OEM radiator is beyond pushing it. If the fins are rotten at the top, but dissipating heat at the bottom that could keep the bottom cooler, but that is some fuzzy physics.

It also could be possible that it is so clogged that there is no flow, and one tank will remain far cooler.

It the petcock on the opposite side of the filler cap?

 

Filler cap in the middle of top tank.
Drain is on drivers side of the bottom tank.

Phantom:
That was the idea of running and draining.
Did as directed on can of radiator flush compound.

 

If you can feel the radiator (don't cut your hand) from top, to bottom you can feel just how far the coolant is flowing.

It sounds like it's completely plugged, and beyond help.

 

Well, the only other thing I can think of, is maybe getting the radiator power flushed, which normally blows holes in any weak spots, anyway. The next step would be a radiator re-core. After that - new radiator time, sadly. I used to take the radiator hoses off and stick the garden hose in it. 'Course, you could just blow a hole in it, instead.

 

My boss junks a lot of cars, so may find a replacement from one of them.
As long as the hoses are on the correct side and it's the right size, I could make it work.
"Hillbilly ingenuity" don't you know.

 

This is not uncommon because the cooling system in an auto consists of various metals and rust does build up also if you have had a gasket leaking oil into the cooling system that gives the rust a coagulant to adhere to it then blocks the narrowest parts of the system which are the cores of the radiator.

One way is a power flush as phantom said, it is very easy to do this yourself by finding an old radiator cap and removing the spring then drill a hole in it to fit a hose connector then connect a water hose to it after that open the drain plug and gently open the tap on the water and see if there is a flow, if that fails try the same thing with a power washer but this will definitely find any weak spots in the rad cores but if it clears the obstruction it is a cheap job to have a couple of cores soldered.

 

Airlock 86.78% sure,you need to bleed the air from the system.

There are loads of vids on you tube not got time to find the best.Basically you find the highest point in the engine cooling circuit where the air will collect,fill system then run engine,bleed air,top up system,run engine,bleed air ect ect. You can also use the bleeder valve method by finding the bleeder valve or burp it using a funnel straight on the radiator.

Think all those methods are here:-D

http://www.youtube.com/watch?v=KfZUahNaDCM

http://www.youtube.com/watch?v=owQcxSrKARA

http://www.youtube.com/watch?v=zUpXgAJ1gjU&feature=related

http://www.youtube.com/watch?v=NReU4wqdK5w&feature=related

A solid blockage would have the same symptom.

 

Drain the radiator, leave the petcock open, remove the TOP hose, tape it off/shut, fill with water from the top, and see if you get flow through the radiator.

If you don't get alot more than a trickle the radiator is toast.