Rusty rad and poor heat

[JTMiller13]

Hi everyone,
New guy here with a new to me truck,
Picked up a 92 silverado and I've got rad problems on the 'backburner' but it's still a pain,

Very rusted out rad hooked to my 7.4, upon first look fluid was swamp brown, determined it was not due to oil and performed several coolant flushes with radiator cleaner, after a couple weeks of daily driving my new green coolant is once again brown and radiator inside is very rusted, open to ideas big and small...

Also! Following this I also replaced my heater core, now I find it doesnt leak anymore but it's very weak and slow to heat the cab...

cheers!

JMiller

 

[Schurkey]

1. Did you pull the two block drain plugs? Flushing the coolant without draining the block before and after is very ineffective. Some guys leave them out "during" the flush.

2. Is the coolant totally topped-off?

3. What is the dash gauge showing for engine temp when fully warmed-up?

4. What is the air temp coming out of the dash vents, when the heater temp is set to full hot, vent, and high blower speed? Same for low blower speed?

 

[GoToGuy]

Are the lines going from block to heater and back clear. No obstructions. What about operating temp? You never said. Should be 195 f° are the lines going in and out of heat exchanger hot? No heat in cab? Check flapper valve positions.

 

[JTMiller13]

Hey guys, I did pull the block drains, coolant and coolant reserve are full, dash gauge shows 70 degrees Celsius or 160 degrees farenheit, not sure about air temp or fan speeds...

The lines are clear of obstructions, lines get hot and cab warms but slowly and weakly, will check flapper positions and thank you both for your time

J Miller

 

[termite]

Hey guys, I did pull the block drains, coolant and coolant reserve are full, dash gauge shows 70 degrees Celsius or 160 degrees farenheit, not sure about air temp or fan speeds...

The lines are clear of obstructions, lines get hot and cab warms but slowly and weakly, will check flapper positions and thank you both for your time

J Miller

160 F is too cold. I’d toss a 195 thermostat in it with another flush and see what you’ve got then. Engine will likely be happier running at 195 as well.

 

[Schurkey]

Hope it's just a failed thermostat.

The other likely cause is rotted foam gasket between the steel cowl and plastic air inlet to the HVAC fan. The cold air coming in past the failed gasket overpowers the heat provided by the heater even if it's working properly. Cab stays cold.

 

[movietvet]

An infrared temp gun can be your friend.