Unusual Heater/AC issue

Bought a 98 recently and found a couple things that are a bit odd. Hoping someone here can point out if maybe i overlooked something.

First,
I found out the heater core is bypassed. I removed it and pressure tested it to about 10 psi. No bubbles. There's still perfectly clean coolant in it. So, why the bypass? There's nothing to indicate a leak anywhere. What am I missing?

TIA

imagodei wrote:

Bought a 98 recently and found a couple things that are a bit odd. Hoping someone here can point out if maybe i overlooked something.

First,
I found out the heater core is bypassed. I removed it and pressure tested it to about 10 psi. No bubbles. There's still perfectly clean coolant in it. So, why the bypass? There's nothing to indicate a leak anywhere. What am I missing?

Second,
my hvac only blew luke warm air. So i've spun the ac compressor to make sure it's not locked up. That checked out, unless i did it wrong? does the clutch need to be engaged?
And i tested the clutch, that clicks down and works. So i'm thinking i'll have to find a leak somewhere after i get the condenser and everything back together.

Last,
I have a new heater core and hoses I plan on using but wanted to see if there's anything else i should do before i start putting the entire system back together.

TIA

1) 10 PSI is not enough. More like 20-30 with boiling water for a test. if there is a leak in the heater core, since it's swaged the leak may only open when things are hot and heavy.

2) the refrigerant may be low, you probably want to evacuate teh system, replace the o-rings on the HVAC hoses, replace the receiver dryer and the orifice valve (put in a variable one if you can find one) and charge it back up. The charge weight is in the service manual.

3) there is not much to the heat part of the HVAC system. Only thing I can think of is inspecting the actuators, the large gears in them usually crack and you can buy just the gear via amazon or eBay, people 3D print them or run them as custom short-run molded parts to sell fairly cheap.

Albertj

albertj wrote:

1) 10 PSI is not enough.  More like 20-30 with boiling water for a test.  if there is a leak in the heater core, since it's swaged the leak may only open when things are hot and heavy.

2) the refrigerant may be low,  you probably want to evacuate teh system, replace the o-rings on the HVAC hoses, replace the receiver dryer and the orifice valve (put in a variable one if you can find one) and charge it back up.  The charge weight is in the service manual.

3) there is not much to the heat part of the HVAC system.  Only thing I can think of is inspecting the actuators, the large gears in them usually crack and you can buy just the gear via amazon or eBay, people 3D print them or run them as custom short-run molded parts to sell fairly cheap.

Albertj

Thanks for the response, I may have found out why the heater core was bypassed. When going to put the new hoses on the adapter pipes that connect to the engine, I decided to take them off from the engine to get a better handle and the check valve basically crumbled and broke apart on the longer one. Is this something I need to replace? I can't find one anywhere...

imagodei wrote:

albertj wrote:

1) 10 PSI is not enough.  More like 20-30 with boiling water for a test.  if there is a leak in the heater core, since it's swaged the leak may only open when things are hot and heavy.

2) the refrigerant may be low,  you probably want to evacuate teh system, replace the o-rings on the HVAC hoses, replace the receiver dryer and the orifice valve (put in a variable one if you can find one) and charge it back up.  The charge weight is in the service manual.

3) there is not much to the heat part of the HVAC system.  Only thing I can think of is inspecting the actuators, the large gears in them usually crack and you can buy just the gear via amazon or eBay, people 3D print them or run them as custom short-run molded parts to sell fairly cheap.

Albertj

Thanks for the response, I may have found out why the heater core was bypassed. When going to put the new hoses on the adapter pipes that connect to the engine, I decided to take them off from the engine to get a better handle and the check valve basically crumbled and broke apart on the longer one. Is this something I need to replace? I can't find one anywhere...

Start by asking at a GM dealer.