How long is too long for radiator flush?

if your thermostat was stuck closed you would know it. you would be pegged on red and probably have a blown head gasket by now.
to the person that said its a blown head gasket...not likely. again man if you are rolling with a blown head gasket it is kind of hard to miss.
if you did have a blown head gasket OP you would see smoke/steam/whatever coming out of the tail pipe. you would also smell it. it would smell sweet and be hard to miss. the # coming out the pipe would be white.
white coming out the pipe is water/antifreeze and blue is oil.
you would know it.

thermostat is easy to replace and it cheap so it wont hurt. if you are strapped for cash you can take it out, put it in a pot of water and bring it to a boil. if it is functioning properly it will open and you will see it.

if its the heater core good luck. gotta take the whole dash out to replace that bitch.

I agree with the thermostat issues.
I have fixed this issue on my old offroad 99 jeep twice.

The first time was a thermostat, the second was a broken blend door actuator axle. The blend door wasn't closing and forcing air through the heater core.

Radiator flushes are good to do in general, but I recommend a flush of your radiator with the heat on high, AFTER replacing the thermostat, they are about 8 bucks for your truck.

A note on radiator flushes. They are highly caustic and will eat aluminum if left in longer than recommended, or improperly diluted.
They are highly effective for build up removal, but are usually done wrong.
The application is completed properly, but trace amounts of the stuff remain when you just clean, drain and refill, so do a full fill and drain on the rad at least twice, with the heat on, reaching operating temp each time, it will remove any of the remaining acid, which over time eats everything in site, including head gaskets, thermostat, o-rings, water pump, heater core, radiator etc,etc...

Good luck



Here's a redneck heatercore flush that works, just disconnect at firewall, don't overpressurize it with water pressure

a reply to: Mandroid7

That`s why I was worried about leaving it in there overnight, but it`s 11pm now so I don`t have much choice.

if I find a big puddle of water on the passenger side floor tomorrow I`ll know that the flush ate the heater core.

a reply to: alphabetaone

it`s the baby blazer S-10

a reply to: Tardacus

You have air in the system most likely, probably in the block. I don't know what mod vehicle you have, but some have a bleeder valve to let the air out while filling. What happens is fluid flows until the air rises to the top and usually it ends up in the heater core and then you have cold air.

a reply to: Tardacus

I think you should be good, and it may help clean better.

24 hrs is the amount of time I let it sit and do it's thing when I flush the inside of jetski supercharger intercoolers, it is basically a aluminum radiator.

longer term trace amounts are bad, basically an acidic coolant that remains and eats it.
I can't stress enough the two flushes, one isn't enough imo.

IF you are seeing the amount of garbage coming from the rad, you heater core is most likely clogged, it has smaller passages than the rad core.

Check the vid I posted above, you just unplug the two 1"ish hoses going into the firewall and flush that bad boy out, then your nice clean coolant can flow through it again. He mentioned not to overpressurize it, so 80psi-ish tap pressure is a little high, so use a valve on the garden hose to control it.

originally posted by: spirit_horse
a reply to: Tardacus

You have air in the system most likely. I don't know what mod vehicle you have, but some have a bleeder valve to let the air out while filling. What happens is fluid flows until the air rises to the top and usually it ends up in the heater core and then you have cold air.

This is good info too. I had to raise the front end of my old Jeep to get the last of the air bubbles out when bleeding the system, they just couldn't come out at level and overheated until I saw in some Jeep blog a similar issue, jacked the front, and sure enough gurgle gurgle, it worked again.
The bubbles, even tiny ones, get sucked into the water pump impeller and cause it to cavitate and no longer pump.

originally posted by: Mandroid7

originally posted by: spirit_horse
a reply to: Tardacus

You have air in the system most likely. I don't know what mod vehicle you have, but some have a bleeder valve to let the air out while filling. What happens is fluid flows until the air rises to the top and usually it ends up in the heater core and then you have cold air.

This is good info too. I had to raise the front end of my old Jeep to get the last of the air bubbles out when bleeding the system, they just couldn't come out at level and overheated until I saw in some Jeep blog a similar issue, jacked the front, and sure enough gurgle gurgle, it worked again.
The bubbles, even tiny ones, get sucked into the water pump impeller and cause it to cavitate and no longer pump.

Yea, the dreaded cavitation also eats impeller blades. I used to rebuild pumps for heavy industry and shipping. Cavitation even eats pump bodies.

Backflush the core at the firewall. Just disconnect the hoses and put light water pressure thru it backwards.

Wow...holy crap do not listen to anyone here. You're running around like a chicken with your head cut off. Stop. Think. Go back to the beginning.

First of all, definitely do not change anything until you check the flow first. Call an autoparts store or go on your favorite parts website to find out what temp your thermostat operates at in a factory configuration. With the engine cool and the ignition off, remove the radiator cap, and start the engine. Watch the temp gauge until it reaches near the temp of your t stat. You will be able to see the coolant lowering and flowing in the radiator tank as the stat opens up. If the flow looks hindered or flows while cool then get back to this thread. Also, lightly touch the upper radiator hose to see if it has hot coolant flowing through it at normal running temp. Let me know.

Trust. Rebuilt plenty of coolant systems. Can do trans, lower motor, done full suspension changes by hand including dipping leaf springs without a machine, bascially rebuilt entire trucks. You gotta diagnose first before you make any moves. You might have put a bunch of work into a simple solution. A common cause of poor heat is a thermostat that is stuck in the open position. Again, check the flow first. It should sit still until the t stat opens at its indicated temp. It might be swirling around in there at low temps (which means you got a stuck t stat and I suspect is likely) and if thats the case a t stat costs $8 and perhaps a gasket. If the parts store tells you a gasket is necessary then get the expensive fel pro gasket with the rubber sealers and some permatex rtv for t stat housings 22071 or they might just have permatex rtv rated for coolant. It'll be there. Also, a t stat housing is tightened down to a specific torque spec. It really is better to always torque down to spec that way you have an even seal all the way around.

Also, don't flush at home. It's nearly impossible to not create an environmental disaster without machinery to suck the coolant out safely and it takes gallons and gallons to properly flush. How are you properly disposing of this waste? Its not recyclable in that condition and shops have to pay to have chemical waste removal companies pick stuff like that up. I highly doubt you're paying for that service. A good shop will give you the contaminate free high pressure distilled water flush your car deserves and will handle the waste for you.

a reply to: Tardacus

Wow...holy crap do not listen to anyone here.

Including the above.
If you are not overheating or below spec why suspect the cooling system?
Heater not working then look at the heating circuit...Fkin simple.
Two words..... heater tap.
Inspect/rebuild/Replace. (the interior mechanism can become separated from the actuating lever)
Then flush through the firewall fittings until you are sure of flow. (No/ low flow - could be heater matrix / heater tap / hoses clogged)
Not just moving the control lever. (can become disconnected and rusty so feels like its doing something)
Also make sure those related hoses are ok too. (can have fissures within the hose than close up like an artery)
Frikkin experts.....

a reply to: seasonal
Excellent

don't put any kind of cleaner thats not specific for radiators. something like CLR might eat at gaskets or make seals expand. if your Blazer is 1996 or newer, then take it to a parts store that has OBD2 scanners you can use. use a scanner and see if the truck knows whats wrong. could save you a lot of time and money.

originally posted by: cancerslug
don't put any kind of cleaner thats not specific for radiators. something like CLR might eat at gaskets or make seals expand. if your Blazer is 1996 or newer, then take it to a parts store that has OBD2 scanners you can use. use a scanner and see if the truck knows whats wrong. could save you a lot of time and money.

yeah cause the heat not working always throws a code huh?

Today I drained the radiator,filled it with plain water, ran the engine for about 15 minutes then drained it again, I did that 3 times to get all that radiator flush out.

Then I flushed the heater core again but this time I took the hoses off.
There was dried rusty crude inside the heater core pipes,i scrapped it off.
The hoses didn`t feel very flexible so I banged them on the cement driveway and I heard crackling crunching sounds,when I held the hoses up a lot of hard shiny brownish crude fell out. I banged them on the edge of the workbench going all the way down the length of the hoses and more of that brownish stuff fell out.I flushed them with water and put them back on and the heat works great.I drove around for about a half hour and the heat remained hot and consistent.

I`m going to flush it with water again tomorrow and put antifreeze in it and test it again but I think I found the problem and fixed it.
I noticed that same hard brown stuff around the inside of the radiator fill spout.
I`m not sure what it is but I would guess that at some point someone put a lot of stop leak in it for some reason.

I just bought the truck so now I`m wondering if there was something leaking that the previous owner got fixed after trying to stop the leak with stop leak or if something was leaking and they used a bunch of stop leak to temporarily fix the problem so that they could sell it.

I did notice that it had green antifreeze in it but this vehicle is suppose to use the orange anti freeze I don`t know if that could be the cause of all this brown stuff.I`ve heard bad stuff about the orange anti freeze so I might use the green stuff.

no not always. i also said it could help, not that it was going to work. sometimes you get lucky and a code saves you the trouble of playing detective a reply to: TinySickTears