A/C questions and ramblings

[BudW]

Your old heater core tube has a “restrictor” in it for a reason.

Before installing, make sure the tube sizes match on both (which should be 5/8” for all 4 tubes - two new and two old).
The ’76-79 F and M-body heater cores use 1/2” and 5/8” tubes. I’m not saying yours are different – only trying to catch a problem before it becomes one.

If needed, some minor tube bending may be required to get the heater core to fit into case correctly.
When I changed the heater core in my ’86 Fifth Ave (same exact heater core), I had to perform a lot of bending, Dremel the core brackets some and other case modifications to get mine to fit correctly - and even then, I cracked the case when bolting the two case halves together.

Those aftermarket (made in China) heater cores do not fit well – from my experience.
Aftermarket evaporator cores – I have had better luck with fitment – but if needed, be very careful about bending those tubes, or better, just don’t do it. The heater core brass is a lot more forgiving than the aluminum is.

I do recommend removing that heater restrictor and reinstalling it, if possible.
Otherwise your heater will always overpower the A/C, correction, heater is just overpowering period (which is not good either in summer or in winter).
BudW

 

[shadango]

Your old heater core tube has a “restrictor” in it for a reason.
View attachment 30595

Before installing, make sure the tube sizes match on both (which should be 5/8” for all 4 tubes - two new and two old).
The ’76-79 F and M-body heater cores use 1/2” and 5/8” tubes. I’m not saying yours are different – only trying to catch a problem before it becomes one.

We had posted about the restrictors here a couple years back when we did the rebuild.....found that then....left it in and it hasnt been a problem.....no idea why its there....think we should pull it out?

If needed, some minor tube bending may be required to get the heater core to fit into case correctly.
When I changed the heater core in my ’86 Fifth Ave (same exact heater core), I had to perform a lot of bending, Dremel the core brackets some and other case modifications to get mine to fit correctly - and even then, I cracked the case when bolting the two case halves together.

Before I take the chance of cracking our perfect heater box or worse, cracking the NEW core and finding out it leaks after reassembly, I think I would rather take our chances and reinstall the old one...it wasnt leaking at all....and looks great.

Those aftermarket (made in China) heater cores do not fit well – from my experience.
Aftermarket evaporator cores – I have had better luck with fitment – but if needed, be very careful about bending those tubes, or better, just don’t do it. The heater core brass is a lot more forgiving than the aluminum is.

The new SPectra heater core appears to be all aluminum, not brass or copper like the old one. Thats why I dont want to try bending it. In fact SPectra distinctly refuses warranty on parts that have been damaged "due to installation". If they are gonna be that way, it would be nice if the parts were RIGHT TO BEGIN WITH. I am really fuming. This is nothing more than CRAP quality control. Makes me question the rest of the part.

I do recommend removing that heater restrictor and reinstalling it, if possible.
Otherwise your heater will always overpower the A/C, correction, heater is just overpowering period (which is not good either in summer or in winter).
BudW

Gotcha......that was our plan...it just sets inside the tube....

We are still waiting for the evaporator...a "4 Seasons" unit.....hopefully a better fit.

 

[shadango]

What really ticks me off is that it looks like SPectra is the ONLY game in town....all the online vendors are selling that brand....and the 'Murray", sold by one place uses the same exact part number....so likely a rebadged SPectra.

 

[BudW]

When a heater core is needed - I highly recommend taking your old core to a radiator shop and have them work their magic. That way you know it will fit (and not break anything in the process.

I broke the evaporator case in my Fifth Ave as well as the heater case in my wagon.
The wagon, I couldn’t wait to get original one fixed (was in a time crunch) – but should have waited and done it correctly.

I hadn’t seen an FMJ heater core made from aluminum, yet – but I guess it was only a matter of time.
The old (leaking) cores from both repairs, are stuffed away in my garage . . . somewhere, for future repairs.
BudW

 

[shadango]

When I did my Cuda's heater core a few years ago I had used a Spectra as I recall and it fit good....and I think I tossed the old one...or its in my metal recycling bin...maybe I should grab it.....

My heart sunk when I opened the box on this one and saw the lack of quality......it weighs almost nothing which I guess is good.....but geez....it just dont fit.

I called Oreilleys and have a "murray" coming in friday.....same exact part number as the spectra so I am not holding out much hope that its vastly better....but if the pipes are right we will use it.....

I can have the AC shop that did the rest of the work recore our old one for $150 *IF* (he said) he can get the core pieces to work with.

This old one isnt leaking so reinstalling as is is high on my list right now unless the murray is a perfect fit.

 

[shadango]

Should have a new aftermarket heater core or two late today or early tomorrow and will know if its "all of them are made that way" as the SPectra tech claims or if he is full of it. If they are also bent wrong, I do plan on having the old core redone. Or maybe we will just reuse it and cross our fingers. trying to get the car back together and functional again. The kiddo seems optimistic about the whole process of yanking it and reinstalling again at some point if needed.....

Also wondering.....we also picked up another new filter/drier....the system has been open now for several days.....figure that dessicant is full of water at this point. And the system will be open for a couple more and then will sit yet a few more til the system is vac'd and filled....

But, the AC shop guy says that this topic is one of those ones that there are all sorts of opinions on.....he and many other pros seem to feel that the vacuuming of the system removes all the water that the dessicant may have soaked up from the air.....that we can replace the drier if we want but he thinks its not necessary....

That said, the filter drier was only $12......so aside from the time it takes to slap the new one in the system, I figure its worth the gamble to use a new one......right?

 

[Aspen500]

The filter/dryer dessicant may dry out if you vacuum long enough but it is recommended to replace it.

The heater core restrictor isn't there really for anything to do with heating and cooling. It's main job is to be a "shock absorber" so the heater core doesn't get a sudden burst of pressure. That can happen if you go WOT and then suddenly go closed throttle. The pressure spike can burst the core in some cases, especially over time. Sort of like when you run a faucet wide open and then turn it off quick. You get that water hammer clunk, especially if your plumbing system doesn't have water hammer arrestors at the shut off valves.

 

[shadango]

The filter/dryer dessicant may dry out if you vacuum long enough but it is recommended to replace it.

The heater core restrictor isn't there really for anything to do with heating and cooling. It's main job is to be a "shock absorber" so the heater core doesn't get a sudden burst of pressure. That can happen if you go WOT and then suddenly go closed throttle. The pressure spike can burst the core in some cases, especially over time. Sort of like when you run a faucet wide open and then turn it off quick. You get that water hammer clunk, especially if your plumbing system doesn't have water hammer arrestors at the shut off valves.

Thanks , that makes sense. Will attempt to reuse it.

The evaporator came today.....overall looks OK but concerned a bit about, again, how the pipes line up.

I have the new evap in the case and the old sitting on top of it, lined up. Notice how the "clocking" of the block from the front looks OK, it is not flat with the case like the oem one would be.....I THINK there is enough leeway in the firewall hole for it to be ok.....I hope....any thoughts??

It is also a litle tight to get it to seat totally on the bottom of the box.....one oif the small feeder pipes is out further than the rest and rubbing on the heater box......think thats an issue long term??

 

[shadango]

Here is from above/side

The pipes are lined up vertically, but the new one is angled toward the middle of the car and seems like it will stick out more....

The new one is missing the flat plate on the top, with the small hole...its for one of the box lid screws....

 

[shadango]

I fussed with it a bit more and once the core was in the box I GENTLY tweaked the block a bit......it yielded pretty easy actually.....its not perfectly lined up compared to the original, but now its not such an extreme angle....just hoping it didn't cause any issues or leaks -- that would suck....I think it should line up ok....

Picking up TWO new heater cores tomorrow to see if they are better than the forst one we got....

Why cant nothing be easy? Why cant the parts just be made RIGHT?

 

[Oldiron440]

Think China made, that's why fit is a problem.
And everything is made I China these days.

 

[BudW]

I wouldn't get worked up about two company’s having the same (or similar) part number. It is not uncommon for most aftermarket part companies to use the same (or close to the) part number.
Also it helps the part stores as well (so the part counter dude can write down 1-part number instead of two before going back to look to see if either brand is on the shelf).

For giggles, I went to RockAuto.com and looked up the part numbers for the front wheel bearings (for FMJ vehicles). Each one of these company’s make their own bearings (. . . I think):
Inner bearing (the larger one)
Timken “Set2”
National A2
SKF BR2
Centric 41091002 (look at last two digits)
Outer bearing (the smaller one)
Timken “Set17”
National A17
ACDelco A17 (note: ACDelco only had the outer bearing listed)
SKF BR17
Centric 41091017
Note: we are lucky, our front wheel bearings are a very common part – that has been used for several decades (well – not so much sense front wheel drive took over).


I would agree with Aspen500, the receiver drier is a reservoir for excess refrigerant and is a filter. The filter portion catches contaminates as well as water moisture (only about a drop worth of water). In this case, there shouldn’t be any contaminates in the system. If the shop allows the vacuum pump to operate for a period of time (about an hour or so), then any water moisture in system will boil and get sucked out. In this case, I wouldn’t spend the money for another drier.

Now if you had a compressor that came apart or blew up, or if system has been open for a period of time (more than a couple of weeks) like with a blown into two pieces hose – then I might consider a drier replacement.

Even though you have a leak – the A/C system will still have residual refrigerant left inside – which makes any air or water moisture difficult to get inside – especially after a week or so.


Your evaporator core fitment issues.
I would not be worried about the large block – for even new Chrysler cores came with issues like that from time to time. If you want, you can go get a large adjustable wrench and give it a slight bend - but personally, I wouldn’t worry about it.

I have a 36” (1 M) version that works pretty well. If a car starts to act up on me, I take it off my pegboard wall and toss the heavy end up and down in my palm a few times – that alone causes the car to start cooperating, um, most of the time.

As far as a tube in contact with plastic – you should be fine there, as well. Plastic will wear faster than aluminum will. If you want, you can place a bit of electrical tape on the core side (really well), or you could also use a heat gun and try to deform the case a bit in that area. I have even seen some technicians trim a small part of the case, then stick A/C duct tape to inside and outside of case– to get some hard to locate cores, to fit correctly.

The imporant part is A/C will produce water condensation via the evaporative cycle of A/C. That water needs a place to go - which should be outside the interior via the drain tube, and not on the floorboard/carpet. Also, the case is under pressure via the blower motor – so keep both items in mind (water drainage and under pressure) if making any case modifications.

The (missing) upper bracket is not a critical issue – except for when tightening (or loosening the) screws/bolt). That bracket is to aid the block from twisting during fastener removal/installation. As long as you keep that in mind – you should be good. I would put a bit of electrical tape on inside and outside of (missing) screw hole – or you could have a hard to find small whistle noise from the pressurized air.

Make sure you use some kind of a seal around all four edges of evaporator core – so that all air travels through the evaporator fins.
BudW

 

[shadango]

I would agree with Aspen500, the receiver drier is a reservoir for excess refrigerant and is a filter. The filter portion catches contaminates as well as water moisture (only about a drop worth of water). In this case, there shouldn’t be any contaminates in the system. If the shop allows the vacuum pump to operate for a period of time (about an hour or so), then any water moisture in system will boil and get sucked out. In this case, I wouldn’t spend the money for another drier.

Now if you had a compressor that came apart or blew up, or if system has been open for a period of time (more than a couple of weeks) like with a blown into two pieces hose – then I might consider a drier replacement.

Even though you have a leak – the A/C system will still have residual refrigerant left inside – which makes any air or water moisture difficult to get inside – especially after a week or so.

The system has been completely open at the evap core connection for a week.....hose has been disconnected this whole time....so its more than just a leak.....do you think there would still be refrigerant inside??

Your evaporator core fitment issues.
I would not be worried about the large block – for even new Chrysler cores came with issues like that from time to time. If you want, you can go get a large adjustable wrench and give it a slight bend - but personally, I wouldn’t worry about it.

I figured that a small amount of tweaking might be needed...just seems like they could do a lot better job on their jigs when building these parts.

I have even seen some technicians trim a small part of the case, then stick A/C duct tape to inside and outside of case– to get some hard to locate cores, to fit correctly.

Well thats good to know....I guess we should be OK.

The (missing) upper bracket is not a critical issue – except for when tightening (or loosening the) screws/bolt). That bracket is to aid the block from twisting during fastener removal/installation. As long as you keep that in mind – you should be good. I would put a bit of electrical tape on inside and outside of (missing) screw hole – or you could have a hard to find small whistle noise from the pressurized air.

Make sure you use some kind of a seal around all four edges of evaporator core – so that all air travels through the evaporator fins.
BudW

Gotcha. Yeah I guess as tight as the core fits in the box it wont move or wiggle once installed....just always freaks me oiut a bit when an aftermarket part eliminates an originally designed feature like this.....will just put some tape over the hole and cross our fingers.

The son refoamed the entire inside of the lid, as was the original situation. So sealing should be good.

 

[BudW]

Did you cap or tape off the hose ends when working with it (to keep bugs from crawling in, or other sources of contamination)?

If a technician is working on an A/C system, then they will not have system apart long enough to cause any problems – unless working in a really dirty or oily environment. If a lot of dirt or oil is in area, they will tape or plug off the hoses (using a collection of plugs they pick up over the years).
The plugs come in several shapes and sizes and a few versions are like:

I have about four containers like this full of caps, cap plugs and other assorted items to plug holes with.

I also have about two dozen other containers like the one above that containing nails, and other hardware (of the same exact type or size). Come to think of it, I just must like nuts (you are what you eat?).

In your case, this manufacture used a metal/tin plate to stop the holes with. Not to seal them – but to keep foreign items out.
I was working on a car after the great Memorial Day flood of Tulsa (in 1984). The dealer I was working at got flooded and the dealer had 60-75 new cars damaged. After dealer reopened, I had an evaporator core to install. The parts dept handed me one that was still in its box - sopping wet - the part was full of flood water. I spent most of a day flushing the core out and getting it dried out enough to install – what a job.

A person can also use tape – if you can find something that will stick but not leave an adhesive residue behind.


Even being open a week or so, I would still reuse your drier and just have the shop evacuate the system for a good while – unless you want to spend a bit more money and feel good about your work.


One thing, a sudden refrigerant leak will allow a lot of oil to escape. A slow leak – not so much of oil escapes.

I would go through the procedures of removing the A/C compressor and drain all oil out of it (hold upside down, turn the clutch hub a few turns and let sit for a while, then re-add refrigerant oil back to the system.
Too much oil is very hard on compressor (oil can’t compress) and ruins things.
Too little oil = a lot shorter compressor life than expected. There is a fine line on proper amount of refrigerant to use.

Attached below is a copy of instructions from my ’86 FSM – which should be identical to your ’80 manual. The only exception is if you are using R-134a instead of R12, then the amount of oil remains the same as listed, but the oil type will be “PAG 46”.
BudW

 

[shadango]

Bud

re: oil.....

There was no sign of major oil leaking anywhere in the heater box so I am thinking the oil should be ok......removing the compressor at this point again means having to order new seals again for the pipes on top......

The shop that did it was charged (no pun intended) with that end of things, oil wise...so I am trusting that he has the right amount of oil in there....

Does the evacuation process remove the oil from the system?

 

[BudW]

Does the evacuation process remove the oil from the system?

No.

Refrigerant oil coats the (insides of) hoses, and such as it moves along the system as the R-134a does.
A slow leak doesn’t leak much oil – but a major leak will lose a lot of oil. My guess is 1/3 to 1/2 of total oil could be lost with a major leak.
When an a/c system holds a total of roughly 5oz of oil – that doesn’t leave much left to keep the compressor parts lubed. There is nothing else that lubricates the moving parts (the compressor).

One thing I liked about the ole RV2 compressors is they had an oil pump and a oil sump – so a person had very little compressor problems to begin. Also they had two different dipstick holes/ports (one on each side of compressor) a person could remove to check oil level with.
Super nice – but also cast iron heavy.

This picture and comment is from my 2002 Town and Country minivan FSM (in blue):
“When an air conditioning system is assembled at the factory, all components except the compressor are refrigerant oil free. After the refrigerant system has been charged and operated, the refrigerant oil in the compressor is dispersed throughout the refrigerant system. The receiver/drier, evaporator, condenser, and compressor will each retain a significant amount of the needed refrigerant oil.

It is important to have the correct amount of oil in the refrigerant system. This ensures proper lubrication of the compressor. Too little oil will result in damage to the compressor. Too much oil will reduce the cooling capacity of the air conditioning system.

It will not be necessary to check the oil level in the compressor or to add oil, unless there has been an oil loss. An oil loss may occur due to a rupture or leak from a refrigerant line, a connector fitting, a component, or a component seal. If a leak occurs, add 30 milliliters (1 fluid ounce) of refrigerant oil to the refrigerant system after the repair has been made. Refrigerant oil loss will be evident at the leak point by the presence of a wet, shiny surface around the leak.

Refrigerant oil must be added when a receiver/ drier, evaporator or condenser is replaced. See the Refrigerant Oil Capacities chart for the proper amount of refrigerant oil to add. When a compressor is replaced, the refrigerant oil must be drained from the old compressor and measured. Drain all of the refrigerant oil from the new compressor, then fill the new compressor with the same amount of fresh new refrigerant oil that was drained out of the old compressor”.

Note: the above specs are about the same for FMJ vehicles, as well.

Note: I somewhat disagree with the above comment about adding “If a leak occurs, add 30 milliliters (1 fluid ounce)” for after a major rupture – a lot more than 1 oz escapes (IMO). Usually you have an oily mess at the site of the leak.
R-134a (and R-12) are (dry) gases and by themselves will NOT show any signs of leakage. Only oil (or dye) will leave a trace of a leak.
I have worked on cars after a hose burst, it has taken a lot of scrubbing and washing to get all the oil removed from hood or wherever the direction of leak was facing.

It is not my intention to have you or anyone else perform unneeded repairs. I only want you to do it right the first time and enjoy the trouble-free A/C for decades to come.
BudW

 

[shadango]

No.

Refrigerant oil coats the (insides of) hoses, and such as it moves along the system as the R-134a does.
A slow leak doesn’t leak much oil – but a major leak will lose a lot of oil. My guess is 1/3 to 1/2 of total oil could be lost with a major leak.
When an a/c system holds a total of roughly 5oz of oil – that doesn’t leave much left to keep the compressor parts lubed. There is nothing else that lubricates the moving parts (the compressor).

One thing I liked about the ole RV2 compressors is they had an oil pump and a oil sump – so a person had very little compressor problems to begin. Also they had two different dipstick holes/ports (one on each side of compressor) a person could remove to check oil level with.
Super nice – but also cast iron heavy.

This picture and comment is from my 2002 Town and Country minivan FSM (in blue):
“When an air conditioning system is assembled at the factory, all components except the compressor are refrigerant oil free. After the refrigerant system has been charged and operated, the refrigerant oil in the compressor is dispersed throughout the refrigerant system. The receiver/drier, evaporator, condenser, and compressor will each retain a significant amount of the needed refrigerant oil.

It is important to have the correct amount of oil in the refrigerant system. This ensures proper lubrication of the compressor. Too little oil will result in damage to the compressor. Too much oil will reduce the cooling capacity of the air conditioning system.

It will not be necessary to check the oil level in the compressor or to add oil, unless there has been an oil loss. An oil loss may occur due to a rupture or leak from a refrigerant line, a connector fitting, a component, or a component seal. If a leak occurs, add 30 milliliters (1 fluid ounce) of refrigerant oil to the refrigerant system after the repair has been made. Refrigerant oil loss will be evident at the leak point by the presence of a wet, shiny surface around the leak.

Refrigerant oil must be added when a receiver/ drier, evaporator or condenser is replaced. See the Refrigerant Oil Capacities chart for the proper amount of refrigerant oil to add. When a compressor is replaced, the refrigerant oil must be drained from the old compressor and measured. Drain all of the refrigerant oil from the new compressor, then fill the new compressor with the same amount of fresh new refrigerant oil that was drained out of the old compressor”.
View attachment 30625
Note: the above specs are about the same for FMJ vehicles, as well.

Note: I somewhat disagree with the above comment about adding “If a leak occurs, add 30 milliliters (1 fluid ounce)” for after a major rupture – a lot more than 1 oz escapes (IMO). Usually you have an oily mess at the site of the leak.
R-134a (and R-12) are (dry) gases and by themselves will NOT show any signs of leakage. Only oil (or dye) will leave a trace of a leak.
I have worked on cars after a hose burst, it has taken a lot of scrubbing and washing to get all the oil removed from hood or wherever the direction of leak was facing.

It is not my intention to have you or anyone else perform unneeded repairs. I only want you to do it right the first time and enjoy the trouble-free A/C for decades to come.
BudW

Thanks Bud. I have to check with the shop to see if they pulled the compressor re: oil......

We didnt see any oil major oil anywhere, to be honest. Of course, no telling how long the system was dead and the evidence could have been cleaned/removed years ago......

 

[shadango]

Well, an update -- so far so good.....AC is cooling......made it thru the night on monday and all day tuesday.....crossing our fingers.

The son noticed a tiny leak at the drier about 20 minutes after we picked it up .....we installed a new drier after the evaporator swap and right before we took the car back for a suck and fill......said he saw some small bubbles. We had torqued the nuts to 100 inch lbs with a beam style torque wrench and used new gaskets....but this time he just tightened them "gootentite".......leak seemed to stop.

So, who knows.

Gonna wait and see, and like I said, cross my fingers that we are done for a while.

On a tangent to this -- anyone know where we can get a new rubber "spout" for the heater box outlet at the firewall? Or what size it is off hand? Ours is missing.....the hole is big enough for a critter to get in there.....

 

[BudW]

Are you referring to the A/C drain tube (or sometimes refereed to an elbow)?

 

[shadango]

Are you referring to the A/C drain tube (or sometimes refereed to an elbow)?

Yep! I have seen some that are just curved hoses, others that narrow down at the end etc.....what should be on this?