I just replace the heater core in our 84SE. After attempting to "burp" the system I ran the engine and noticed an intermittent hissing coming from the vicinity of the core. I can move the temp slider from Hot to Cold and it goes away.
The heater works great, and all seems good, however the hissing makes me think there is air in the system. Still, after burping the system I wondered if I was doing it right. I found a link in this forum to a page that should have instructions but the link was broken.
If anyone has ideas one way or the other (air in the system or not) I welcome suggestions.
The heater works great, and all seems good, however the hissing makes me think there is air in the system. Still, after burping the system I wondered if I was doing it right. I found a link in this forum to a page that should have instructions but the link was broken.
I've posted the following numerous times. My Fieros never overheat. My heater cores never hiss.
quote
Originally posted by Patrick:
* Begin procedure with a cold engine.
* Make sure rad cap is the proper one for Fiero use. The catalogs are wrong! You want a non-vented one, * Check that the coolant reservoir and the small hose to the rad are both in good shape. Otherwise air gets sucked in. * Ensure that coolant level in coolant reservoir is at the "Cold" level. * Position rear end of Fiero higher than the front. * Remove thermostat housing cap and thermostat. * Remove radiator cap. If coolant runs out, put rad cap back on. If coolant doesn't run out, leave it off. * Add coolant to thermostat housing. If rad cap is still removed, continue to fill until coolant runs out the top of the radiator. * Re-install rad cap.
* Continue again to add coolant at the thermostat housing until you see the level come up to where the thermostat normally sits. * Put thermostat cap on (without the thermostat) and turn just barely enough to hold cap on. * Start engine and run for about 30 seconds. * Remove thermostat cap and check coolant level. * Repeat last four steps until coolant level no longer drops.
* Re-install thermostat and thermostat housing cap.
As long as there are no blockages anywhere in the cooling system and the water pump is circulating coolant, you should be good to go.
* After several heat cycles of the engine/cooling system, double-check coolant reservoir level... just in case there's a coolant leak.
[This message has been edited by Patrick (edited 06-23-2022).]
A hissing noise from the heater core would indicate air, but it would also indicate blockage of some sort. I don't think it is supposed to be that difficult for any fluid to go through the core.
You DO NOT need to "burp" as many here say. When coolant system is good... all air moves to radiator then out of system. Just get big air out at Tstat and rad covers then system does the rest. It can take a few heat/cool cycles to remove all the air. Make sure overflow tank and tube is good and filled.
If you move controls and noise stops... Problem likely is not heater core. Noise is heater/AC box. Examples: Air Flow making noise. Crap in heater box or blower. Clean blower, resistor set, etc. You can remove resistor and blower w/o problems. use search.
------------------ 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)
Thanks for all the replies. I will cycle it a few more times. Right now we are getting ready to be hit by this storm moving through tonight. I am hoping to take a closer look at it this weekend when the weather is nicer. Thanks again.
I just replace the heater core in our 84SE. After attempting to "burp" the system I ran the engine and noticed an intermittent hissing coming from the vicinity of the core. I can move the temp slider from Hot to Cold and it goes away.
The heater works great, and all seems good, however the hissing makes me think there is air in the system. Still, after burping the system I wondered if I was doing it right. I found a link in this forum to a page that should have instructions but the link was broken.
If anyone has ideas one way or the other (air in the system or not) I welcome suggestions.
if the noise goes away when you move the temp lever the heater core door closes so it may very well be a air leek at or in the heater core. By closing the door you are putting a sound barrier between the noise and the cabin.
Did you pretest the core before you put it in? put a garden hose on one end and fill it slowly with water, then when it is full put your thumb over the other outlet. if it hold water it isn't the heater core, but it could be the hose connections. But I don't see it being the hose connections under the hood, the only thing that makes me think it is the heater core is the noise but if it is it maybe air now but will eventually become antifreeze on your floor.
But then I could be wrong, I have been before.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Originally posted by 84fiero123: Did you pretest the core before you put it in? put a garden hose on one end and fill it slowly with water, then when it is full put your thumb over the other outlet. if it hold water it isn't the heater core, but it could be the hose connections. But I don't see it being the hose connections under the hood, the only thing that makes me think it is the heater core is the noise but if it is it maybe air now but will eventually become antifreeze on your floor.
But then I could be wrong, I have been before.
This test is useless. Even "Dead" cores can pass static test and fail at working pressure. If the core is bad then you likely leaking coolant on your floor.
Using hose/air to pressure test w/o regulator can break the core etc. Test pressure is 20-22psi Max for many parts. Normal working pressure in 15-16psi for most systems.
Air in the heater core and plumbing will move to radiator then out of system. Again, Could take a few heat/cool cycles to purge air out of system.
[This message has been edited by theogre (edited 02-24-2016).]
Originally posted by theogre: This test is useless. Even "Dead" cores can pass static test and fail at working pressure. If the core is bad then you likely leaking coolant on your floor.
Using hose/air to pressure test w/o regulator can break the core etc. Test pressure is 20-22psi Max for many parts. Normal working pressure in 15-16psi for most systems.
Air in the heater core and plumbing will move to radiator then out of system. Again, Could take a few heat/cool cycles to purge air out of system.
Since normal household pressure is 40+ psi, the hose test mentioned by Steve is far from "static". Still not the best test since you can't regulate the pressure accurately.
[This message has been edited by Neils88 (edited 02-24-2016).]
Originally posted by Neils88: Since normal household pressure is 40+ psi, the hose test mentioned by Steve is far from "static". Still not the best test since you can't regulate the pressure accurately.
I reading he's filling but not any or enough pressure for that test.
Say the hose is clamp on one tube and thumb is on outlet side and leave water on... Many people can't hold more then a few PSI on ~1/2 tubing w/ just thumb pressure and many dead cores can fake pass w/ low pressure.
You can test w/ any hand pump and basic items. I used junk heater hose, old clamps and a old spark plug to seal up and hand pump w/ gauge to test them. If gauge moves after reached ~15psi then dunk the whole thing in 5 gal bucket to see where the leak is. Many cheap pumps can leak in the pump or gauge is off. Gauges w/ scales under 2-3 inches and 100+ psi are hard to read at low end. so don't go over 20psi.
You can test w/ any hand pump and basic items. I used junk heater hose, old clamps and a old spark plug to seal up and hand pump w/ gauge to test them. If gauge moves after reached ~15psi then dunk the whole thing in 5 gal bucket to see where the leak is. Many cheap pumps can leak in the pump or gauge is off. Gauges w/ scales under 2-3 inches and 100+ psi are hard to read at low end. so don't go over 20psi.
That reminds me of something I posted about more than seven years ago. Here's the picture I uploaded...
You just never know when an old bicycle inner tube might come in handy.
This isn't one of those new fangled hear cores with swivel inlet/outlet pipes is it? I put a new heater core in my sisters car, some newer Pontiac, not a Fiero but it had swiveling pipes. That has 2 more places that are possible points of leakage.
Every heater core I have ever bought had a little one page instruction sheet that said pretest the heater core for leaks, every manual I have ever read has said pretest it before installing it. The water is a useful test, by putting you thumb over the heater core outlet even if it is just a couple of lbs. is better than not testing it before the install. Air will escape easier than water on a hose connection or any leak in the heater core.
if you are that concerned about over or under pressurizing the core than put a pressure gauge on the open end, they are cheap enough. an old vacuum/pressure tester in.
But not doing any kind of pressure test of the core before putting it in is a mistake and can cause problems if the core did get damaged during shipping. How many of us here have gotten a bad brand new part that was damaged during shipping?
Old school rules right Patrick.
If you have a vacuum pump you can do the same test in reverse, so to speak, use a vacuum pump with the other end capped and pump it up to 15 lbs. and if it keeps losing pressure then you have a leak somewhere, at the hoses is the first place to check, then everywhere else.
edit to add
frig I forget now
Oh ya, here is one you can't say is over or under pressure, connect the heater core to the hoses in the spare tire area and put the core on some flat surface, do not install it in the heater core box leave it right out where you can watch it. Now start the car, if the core is leaking you will see it soon enough.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Detroit iron rules all the rest are just toys.
[This message has been edited by 84fiero123 (edited 02-25-2016).]
UPDATE: I had a little time on Sunday and tried to burp (the system). I did have to add some coolant. While I have not had a chance to do it the recommended 4 times, in the meantime, I had to move the car out of the driveway, so I drove down the street to the grocery (about 3 miles). Here are some observations ...
The hiss sound only occurs when the defrost OR the AC (which does work) is on regardless of the temp selected. I got out of the car and left it to idle. The hiss is especially loud under the hood and seems to be located around or behind the AC unit. So, I came to realize since I owned the car I never really ran the AC or defrost (due to the leaky core).
I did not get to spend a lot of time with the car as we had a beautiful weekend here and I wanted to spend it doing other outside projects. I hope to be able to investigate this sound in the forward compartment further. Thanks for all the responses.
I had a little time on Sunday and tried to burp (the system). I did have to add some coolant. While I have not had a chance to do it the recommended 4 times...
Where did you read it needed to be done "the recommended 4 times"?
quote
Originally posted by Jon84:
The hiss sound only occurs when the defrost OR the AC (which does work) is on...
Keep in mind the A/C is running anytime Defrost is selected.
[This message has been edited by Patrick (edited 02-29-2016).]
Originally posted by Jon84: The hiss sound only occurs when the defrost OR the AC (which does work) is on regardless of the temp selected. I got out of the car and left it to idle. The hiss is especially loud under the hood and seems to be located around or behind the AC unit. So, I came to realize since I owned the car I never really ran the AC or defrost (due to the leaky core).
The hiss is the refrigerant. It's entirely separate from the heater core. You could have the A/C pressure tested; it might be low on refrigerant. That can increase the hissing noise.
Originally posted by Patrick: Where did you read it needed to be done "the recommended 4 times"?
Now that you mention it I cannot find it! I went back an looked and I must have mis-read or picked it up from someplace else. I have been installing everything from a security system on a house to a car stereo this weekend. Too many irons in the fire I guess.Sorry about the confusion.
Originally posted by David Hambleton: The hiss is the refrigerant. It's entirely separate from the heater core. You could have the A/C pressure tested; it might be low on refrigerant. That can increase the hissing noise.
