Working on my brothers 2001 Expy. He has very luke warm heat in the front with the fan speed on the lowest setting (I'd barely even call it warm), which gets colder as you increase the fan speed. The rear heat is cold. Never gets close to warm at any fan speed.
1) The vehicle has never overheated, but the coolant level was low. We added coolant,elevated the front end, squeezed every hose and seem to have got any air out of the system.
2) There is no leaking at all from the heater core that we can find any where.
3) There are no weird smells coming from the system at all.
4) No "clicking" noises that we can hear from the blend door area of the dash.
5) Heater core hoses running into the firewall get almost too hot to hold onto, but the hoses in the back of the truck are ice cold.
From this point we are unsure of what to check next and need some help!! Kind of seems like maybe the heater core is blocked - maybe?? I would really hate to tear the whole dash out if we don't need to though! If the core is blocked, how do we flush/backflush the system??
Also, the truck has 228,000 miles (still runs excellent! - just cold) and he is unsure when the coolant was flushed last. What is the correct way to flush the system?
5) Heater core hoses running into the firewall get almost too hot to hold onto, but the hoses in the back of the truck are ice cold.
This sounds like a blend door issue for the front, but a lack of coolant flow to the rear. The lack of flow could be due to a plugged core for the rear unit.
The best way to flush the core is to remove the heater hoses going to it and blast water through the core with a garden hose. Preferably in both directions.
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We disconnected the heater core lines at the firewall and flushed the front and rear lines with the water hose and air compressor. All kinds of rust/chunks came out!! Now, the rear heat has improved dramatically, but the front is still just luke warm. We are gonna reflush with air and water and then cleaner and see what happens.
This sounds like a blend door issue for the front, but a lack of coolant flow to the rear. The lack of flow could be due to a plugged core for the rear unit.
The best way to flush the core is to remove the heater hoses going to it and blast water through the core with a garden hose. Preferably in both directions.
It was actually 2 plugged heater cores! We removed the heater hoses going in to the fire wall and blasted the heck out of them (front and rear) with a garden hose and the air compressor. We got the back working first and with repeated efforts, finally got the front working as well.
I think the trick is attacking the "outlet" hose for front or back first. What worked for us was blasting everything out with the air compressor and then refilling it with a high pressure stream of water and then blasting with the air compressor again over and over until no particles come out and the water is crystal clear on the out let hose, then doing the same thing to the inlet hose. Before we hooked everything back up for the last time, the water was so clear it looked like you could drink it . Now, the heat is very very hot in the front and back!!
How do I tell which are the inlet and outlet hoses for the front and rear heater cores?
That's always a good question for any vehicle. What I usually do is turn the heat on full blast (engine running) then feel the two hoses. The inlet hose will always be slightly warmer than the outlet hose.
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. Now, the heat is very very hot in the front and back!!
