How long is too long for radiator flush?

My heater wasn`t working so I flushed the heater core with just plain water, it blew heat for about 4-5 minutes and then it went back to blowing cold air.
The second time I flushed the heater core I used water then some CLR let it sit for about 5 minutes then flushed it with water again.It blew hot air for about 5 minutes then went cold again.
The third time I flushed it I did the CLR again, let it sit for 5 minutes, and flushed it with water again. The heat blew for a little longer this time about 10 minutes then got cold again.

I figured that there must be crap in the radiator that is circulating and blocking the heater core so I bought some gunk brand radiator flush and poured it in while I was in the store parking lot.I drove 30 minutes home but it wash dark by the time I got home.

The container says to run the engine for 15 minutes with the flush in it and then flush the radiator with water.
well it`s dark so I`m going to wait until tomorrow to drain and flush the radiator, do you think leaving it in for so long will cause a problem?

my other question, if the gunk radiator flush doesn`t fix the problem would it be harmful to pour the CLR in the radiator and run the engine for a bit and then flush it out?

I`m worried that the CLR will mess up the gaskets it comes in contact with.

a reply to: Tardacus

Have you checked the thermostat?

a reply to: seasonal

My grand father worked as a wind tunnel engineer at Ford. I remember he told me once if heat is not working on a car your thermostat is not opening. Or you have a blown head gasket.

Good choice seasonal.

dp

Try this,it's been a long time since I messed with the radiator stuff, I think I have it right.
If the thermostat opens, it lets more water into the block to cool the engine, it shuts to reduce water to heat up. Yours may be stuck open, "flooding" water threw the block and not allowing the water to heat up. After allowing the car to idle and heat up is the hose warm/hot or OH MY God hot?

a reply to: Tardacus

a reply to: Tardacus

When the mixture of boiling water and sodium hydroxide melt through the radiator core, that would be too long. Lol

I did mine once, I ran the engine for about 5 minutes first. Drained it and then filled with warm water and rad flush. Ran it until it got to temperature and then ran for another 15 minutes. Let it cool down for 30 minutes, drained again. Let it cool down for an hour and filled it with 50/50 antifreeze.

If you want to mix your own antifreeze and water, make sure the water is distilled or de-ionized as some vehicles will build up an electrostatic charge in things like the heater core and eat it away through electrolysis.

Cheers - Dave

originally posted by: seasonal
a reply to: Tardacus

Have you checked the thermostat?

Definitely a good starting point. Yesr make and model would be very helpful with trying to diag it for you if ya dont mind.

a reply to: Zerodoublehero

If his radiator was plugged the heat wouldn't "leave" the engine very efficiently and his car would be HOT, seems like heat would be easy.

Also if you are getting water through your heater core it is more than likely it isnt clogged seeing as how water is going through it. Could also be a problem with the blend door/ vent system.

a reply to: Tardacus


Watch your temperature gauge during your tests. There is a thermostat installed, right? A thermostat stuck closed will quickly overhead your car in normal driving conditions.

If it is stuck open or none is installed, the heater may not get too hot. Actually, turning the heater on with no thermostat in the engine will even cool the coolant more as it increases the radiation effect from the various radiation surfaces. I suspect there is no thermostat installed.

a reply to: Tardacus


Typically what I've done (to myself) is use too much sealing compound on the thermostat causing it to stick open. Though even with no thermostat you should get SOME heat.


A good first sign that your heater core is bad would be steam coming out of the vent when you turn the heat on and the engine is at running temperature. Frankly if I were you, I would get a pressure test done on the radiator / cooling system.


Also, make sure it's the properly rated thermostat, if your vehicle is rated to open at 180 degrees and it isn't opening until 200 degrees (which it never may do) that could explain it too...it sounds as though your thermostat simply isn't opening and closing.

originally posted by: seasonal
a reply to: Zerodoublehero

If his radiator was plugged the heat wouldn't "leave" the engine very efficiently and his car would be HOT, seems like heat would be easy.

Never said his radiator was plugged. He would have an enginw over heating problem if that was the case because the coolant would not be able to circulate.

a reply to: seasonal

not yet but now it will be the first thing I check tomorrow

The water temp gauge on the dash only goes up to about 160-170 degrees even after several hours of driving,i have a feeling it should be higher than that up around 190-200 degrees?

The first 2 times that I flushed the heater core a lot of rusty water and soft chucks of rust came out,the third time I flushed it rusty water came out for about 5 seconds then the water ran clear.

a reply to: Tardacus


I believe that modern thermostats are rated at 192 degrees. far hotter than in my old hotrodding days of about 165 degrees.

a reply to: Zerodoublehero

That was the first thing I checked, I removed the blend actuator box and moved the temp control knob from hot to cold and the actuator motor worked. then I turned the blend door by hand to make sure it moved easily and wasn`t stuck.

a reply to: Aliensun

now that you mention it I seem to remember that the heat would stop when the temp gauge got up to around 150 degrees, when the gauge was below that it had heat, not real hot heat but definitely heat.

originally posted by: Tardacus
a reply to: Zerodoublehero

That was the first thing I checked, I removed the blend actuator box and moved the temp control knob from hot to cold and the actuator motor worked. then I turned the blend door by hand to make sure it moved easily and wasn`t stuck.

Definitely start with replacing the thermostat. Depending on the type the vehicle you have you can probably pick one up for less than 30 bucks. If its stuck open it will let rhe coolant flow through the radiator before the engine gets to proper operating temperature which would not let the coolant get hot enough for you to be able to get good heat from the system.

Try that hopefully a cheep and simple fix! And that is the most likely scenario based on the conditions.

a reply to: Zerodoublehero

I`ll do that tomorrow I`ll take it out ( if there`s one in there) and replace it.after reading the comments here I have a feeling I`m going to find the thermostat is rusted open.

it`s a 1998 blazer the auto parts store should have a thermostat for it in stock.


I wonder if there is like a flow control valve that that shuts off water supply to the heater core if the engine temp is low?

I didn`t see anything on the heater core hoses.

Sounds like you will have heat in no time. I believe that particular vehicle its fairly easy to do a thermostat replacement so you should be fine. Just make sure you get a new gasket also. That way you sont end up having any leaks afterwards.

Eta. To answer that question no. Its a much older vehicle and its pretty straight forward. Theres always coolant going through the heater core. You only feel the heat when the blend door opens and the fan blows the hot air into the cab.

originally posted by: Tardacus
a reply to: Zerodoublehero

I`ll do that tomorrow I`ll take it out ( if there`s one in there) and replace it.after reading the comments here I have a feeling I`m going to find the thermostat is rusted open.

it`s a 1998 blazer the auto parts store should have a thermostat for it in stock.


I wonder if there is like a flow control valve that that shuts off water supply to the heater core if the engine temp is low?

I didn`t see anything on the heater core hoses.

Full sized Blazer or S-10? From what I recall, the S-10's were notorious for thermostat issues.