96 ram 1500, no heat.
checked heater core, feed line gets hot, return doesnt, can easily blow thru hoses and core.
Im a bit stummped here.
Ideas guys ????
Tia

 

You either aren't getting flow thru the core, or the blockage is somewhere else. Might be just low on coolant as well.

 

I removed heater core, inspected, put back in and refilled

 

if you had the heater core or you should have replaced it.

 

If supply to heater core is hot and core isn't plugged I'm guessing air in system/cavitation

 

I actually thot about that.

 

So I'm dealing with this now on a '98. I tried the Maddox vacuum fill after a timing cover re-seal.

Unfortunately no heat from vents afterward. I was finally able to get "warm" air by taking the front as high as my AC Hydraulics jack would go and using a spill-free funnel. I got it take noticeably more coolant this way.

I could try to drive RF up my RTI ramp but without TAD's I'm not sure how far I'd get and not sure it would do any better than what I've already done...



Still, I'm not thrilled with the heat performance. Really don't know what more could be done. Heater core was new a year ago. Line into core hot, line out of core hardly even warm.

 

add a T like I did.

 

Ok so kinda weird experience today but I'm posting here because my symptoms were same as OP: positive core isn't plugged but outgoing heater hose cold.

As much as I dislike novellas, I must first mention that earlier today I tested the rad cap because it just didn't feel "right". It initially tested pathetically but I found if I pumped it up rapidly with my tester it would hold, so I figured "meh, good enough."

After attempting to bleed as shown in pic above, I had to leave the shop for awhile so I let it off the jack and shut it down. Once I returned I was actually able to get just a little more in the radiator while it was shut down (and now cold). I kept trying to burp any little bit I could by squeezing upper rad hose and I did see a few bubbles escape.

Then I started it up and went for a test drive. At this point HVAC heat was inexplicably good to borderline great. Ok, don't know what happened but it's better to be lucky than good I suppose.

I got into town and dropped from highway speeds to ~30 and noticed dash gauge was at 210 (perfectly vertical) and considering climbing beyond that but never did much. I understand the gauge is more of a "guide" but it had never run this hot before while idling for ~45 minutes in my shop or on the highway, so I was suspicious.

I stopped at the store and took a peak under vehicle to find that the rad cap had allowed some coolant by and rather than going down the poorly-fitted hose to the reservoir it was just dripping. I cracked the cap (carefully) and the system gurgled a lot but no additional coolant escaped.

I decided I was done trusting this questionable rad cap -- there was no reason it should have blown off if I wasn't overheating and I have no credible reason to suspect head gasket issues. Thermostat is a new Motorad but it's the higher end "Ultra" and not a fail-safe. I went to my FLAPS and grabbed another craptastic Murray cap -- they feel like they belong on a child's toy like an EZ-Bake oven but it was all they had.

After this the vehicle was great. No more 210 on temp gauge and heat from vents was still good.

At this point my working theory (aka arguable fiction) is that there was still air in the system. Since I would assume hot air expands more than hot coolant (is this true??) it helped to overcome my weak rad cap....and it would seem (more fiction) an air pocket contributed to my weird running-hotter-than-normal condition, so perhaps cavitation which was relieved when I cracked the cap at the store.

I drove it more and repeatedly went from highway speeds to ~35 mph for a couple miles then repeat but the gauge stayed well under 210 while HVAC heat was still very good. At this point I called it good and returned it to my non-profit.

TL;DR: these systems are a biznatch to burp

 

Air does indeed expand a LOT more than coolant as it heats.

Air trapped under the thermostat will make it look like the engine is overheating, but, it isn't really. After the thermostat cycles a time or two, the air should be released.

Also, the cooling system being under pressure raises the boiling point..... however, due to your craptastic cap, it was unable to build pressure......