Just slightly warm air from Heater (Page 1/1)
Oz NOV 01, 12:09 PM
I read up on some previous discussions around luke-warm air from the heater (87 GT). I know the diverter is moving into place when I move from cold to hot. The system seems to be purged of all air and I know coolant is being circulated. So I took another approach.

I got my infrared temperature gun out. At full operating temp (with 195 thermostat) the engines top coolant hose (right off of the thermostat cap) read ~180. Sounds right considering it was 45 degrees outside. The driver side radiator hose up front read ~145. The bottom hose on the heater core read ~130. The top hose on the heater core read... 85. (Without the fan on moving air through the core.)

Just my diagnostic thoughts, but that is likely the original heater core and it sounds to me like it's just plugged up. So I ordered a new one. We shall see.

I just wanted to document my process for someone else that might be looking for a way to diagnose a similar challenge with cold-ish air coming from their heater.

Any other thoughts are very much welcome!
theogre NOV 01, 01:32 PM
Is a new T-stat? T-stats do fail & maybe stay open. Some aftermarket ones are design to fail open.

Core can be plugged or anywhere in that loop blocking flow.
See https://web.archive.org/web...erocave/heatmelt.htm
Get under the car to check heater pipe(s) aren't crushed etc.

If the core is plugged, the rest of cooling systems very likely have problems too.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Mike in Sydney NOV 01, 05:41 PM

quote
Originally posted by Oz:

I read up on some previous discussions around luke-warm air from the heater (87 GT). I know the diverter is moving into place when I move from cold to hot. The system seems to be purged of all air and I know coolant is being circulated. So I took another approach.

I got my infrared temperature gun out. At full operating temp (with 195 thermostat) the engines top coolant hose (right off of the thermostat cap) read ~180. Sounds right considering it was 45 degrees outside. The driver side radiator hose up front read ~145. The bottom hose on the heater core read ~130. The top hose on the heater core read... 85. (Without the fan on moving air through the core.)

Just my diagnostic thoughts, but that is likely the original heater core and it sounds to me like it's just plugged up. So I ordered a new one. We shall see.

I just wanted to document my process for someone else that might be looking for a way to diagnose a similar challenge with cold-ish air coming from their heater.

Any other thoughts are very much welcome!



Sounds like you diagnosed it correctly.

I had a similar problem on the Bride's VW Tiguan. Dealership wanted almost $2000 to replace the heater core. I disconnected the hosed from the heater core out side of the passenger compartment and back flushed the core and goaat all kinds of sediment and crap out of the core. Then, I jury rigged a bucket higher than the core so I could hold radiator flush in the core and I let it stand over night. I back flushed again and got even more junk out and when the water flow was clean I reconnected the hoses to the engine block. Problem solved.

I'm not saying this will fix your heater core - and some folks on the forum will tell you why tjhis shouldn't be done - but, hey, I saved $2000.

Good luck.
Oz NOV 01, 07:12 PM

quote
Originally posted by theogre:

Is a new T-stat? T-stats do fail & maybe stay open. Some aftermarket ones are design to fail open.

Core can be plugged or anywhere in that loop blocking flow.
See https://web.archive.org/web...erocave/heatmelt.htm
Get under the car to check heater pipe(s) aren't crushed etc.

If the core is plugged, the rest of cooling systems very likely have problems too.




Yep, brand new 195 t-stat. It had the same issue with a 160 t-stat.

I'm happy that you said that if the heater core is plugged, that the rest of the cooling system likely has problems too. Because it does. It will overheat if the outdoor temperature is over 80 degrees. I've been messing with the system all summer and decided a new radiator or water pump was in my future. Maybe a new heater core will be the easier, cheaper answer to all the issues.

All that said, I will get underneath to see about any crushed pipes, just to triple check every possibility. But a new heater core is on the way.

Thanks for the input!
Oz NOV 01, 07:15 PM

quote
Originally posted by Mike in Sydney:


Sounds like you diagnosed it correctly.

I had a similar problem on the Bride's VW Tiguan. Dealership wanted almost $2000 to replace the heater core. I disconnected the hosed from the heater core out side of the passenger compartment and back flushed the core and goaat all kinds of sediment and crap out of the core. Then, I jury rigged a bucket higher than the core so I could hold radiator flush in the core and I let it stand over night. I back flushed again and got even more junk out and when the water flow was clean I reconnected the hoses to the engine block. Problem solved.

I'm not saying this will fix your heater core - and some folks on the forum will tell you why tjhis shouldn't be done - but, hey, I saved $2000.

Good luck.



Thanks for your insight as well! New cars have some crazy costs associated with them. I considered having a local radiator shop 'core' this one. But replace heater cores for the Fiero are pretty cheap. Anything over a couple hundred bucks for a new core would definitely have me trying to flush it out first just like you did!
Oz NOV 08, 06:22 PM
For posterity and searches that might find this topic;
I replaced the heater core today. Dumping it out the antifreeze was chunky and brown coming out of one side. The new core was much less restricted blowing air through it.
Starting it up, there was warm air much more quickly and as the car got up to temp the hot air was actually hot while the ambient air temp was 45 degrees. Huge win.

Side note; I also noticed that the cooling system didn't cycle full range as quickly or as often. The thermostat was cycling open and closed while it idled instead of the fan kicking on. I'm optimistic that the cooling system will perform better in the summer.
Patrick NOV 08, 06:51 PM

quote
Originally posted by Oz:

I replaced the heater core today. Dumping it out the antifreeze was chunky and brown coming out of one side.



Unless you did a full flush/reverse flush of the entire cooling system (as Mike was suggesting), I'd be concerned that there's more "chunky and brown" stuff elsewhere that could lead to future blockages.

[This message has been edited by Patrick (edited 11-08-2023).]

Vintage-Nut NOV 08, 07:55 PM

quote
Originally posted by Patrick:
Unless you did a full flush/reverse flush of the entire cooling system....



until the drained liquid is nearly colorless,


quote
Originally posted by theogre:
...the rest of cooling systems very likely have problems too.



To me, the complexity of cleaning the Fiero coolant system requires several flushing’s.

And my local water hardness has minerals, so I don't use a 'garden hose' - I use distilled water instead.

The cooling system fluid capacity of the 2.8L engine is 13.8 quarts; however, when draining it for the first time will only measure ~7 quarts. So, keep in mind that the fully flushed coolant system has ~7 quarts 'water' in the engine block and other 'pockets'.

The bottom-line is don't use a premixed 50/50 Antifreeze/Coolant - pour in full strength concentrate antifreeze.

Good luck with your optimistic mood........

[This message has been edited by Vintage-Nut (edited 11-08-2023).]

IMSA GT NOV 08, 08:31 PM

quote
Originally posted by Patrick:

Unless you did a full flush/reverse flush of the entire cooling system (as Mike was suggesting), I'd be concerned that there's more "chunky and brown" stuff elsewhere that could lead to future blockages.




I'll just add, if someone mixed standard green antifreeze with Dexcool orange type, the combination can gel up and block the cooling system. It NEEDS to be 100% flushed out.
Oz NOV 13, 01:47 PM
All green, never orange. Thankfully.

Yes, I could have done a better flush.

I drove it for a few weeks before a catastrophic hose failure and all the coolant and floating debris was forcefully removed for me via the lower water pump hose.
I replaced all the big hoses and ran new coolant/distilled water for a month before I replaced the heater core. The coolant I drained / spilled during the core replacement was pretty clean. So it seems that the old heater core was a really good debris filter and retainer.

That said, I'm sure the primary radiator is not clean. A spring project will be a flush and likely a new radiator --should this one be too plugged. The heater core is cheap and easy to replace, so worst case I'll replace the heater core again --if it looks like there was/is still a lot of stuff loose in the system.

Final thoughts. I drove this Fiero when I was a college student in the mid 90's. I didn't do a very good job with maintenance back then and I used (very hard) tap water instead of distilled water in the system.