HEATER CORE BOX VENT LEAK

[TANTO]

After with winter of 2022 I found a quarter sized spot of anit-freeze on my garage floor that I can see came from a the ½” rubber 90 degree “to air” elbow right under the heater core box area. I assume this elbow is to prevent moisture in the heater core plastic “box”. So I pressured tested the coolant system with fine results, celebrated with an adult beverage, changed the fluid and dismissed it. But just now i found another spot, again seeing the rubber elbows inside is wet with coolant. So I again pressure tested 16 lbs and it’s shows zero loss over 24 hrs. I must have a very slight coolant leak of the core or a hose only under heavy load, right? My coolant changes are by the book with acura fluid and the required burping. Anyone have this happen? Comments greatly appreciated as usual. Thanks!

 

[SWFL_NSX]

I'm having trouble understanding where the "to air" hose is that you're talking about. Do you mean the drain hose that runs from the HVAC unit to under the car?

If so, make sure the liquid is actually coolant and not just water. It is normal for condensation to form around the evaporator core while the AC is running, and then drain out the hose and onto the garage floor. Here in FL this generates quite an amount of water!

If it's definitely coolant you may want to reach out to Joe Gutteri @nsxspeedfreak and see what your options are. He refurbishes the seals on the HVAC; if you need to take the dash out to get the heater core repaired you'll want to have him check it out while it's out of the car.

 

[TANTO]

Yes it is the hvac box drain and it IS coolant. Joe Gutteri@nsxspeedfreak mentioned, I don't find a member when searching, is this an email? Thanks.

 

[Kaz-kzukNA1]

Joe's userID is @nsxspdfreak.
'Mention' feature may not work (never worked for me so no notification received) so search the userID and send conversation.

RHD model so different configuration from LHD but you'll get the idea.

What year model?
Heater core on early models is in brass.
Later one or OEM replacement in aluminium.
You can check the material by looking at the 2 pipes at the front bulk head.

What the colour of your coolant?
Type 2 is Blue but some Honda/Acura garages use green.

Do you have leak detector green dye in your a/c refrigerant?
When was the last time you checked the a/c refrigerant pressure?
You can do quick check at the sight glass on the a/c receiver/drier.

Kaz

 

[TANTO]

Thanks Kaz for the referral. I'm LHD 1992, blue type 2 honda, AC working fine. I just have to bite the bullet and pull the unit and find or repair the core(appears i can get one from Europe). And a repair is possible. When i was growing up in the 70's we had radiator shops who would pressuring the core, drop the core/radiator in, find the leak, solder it up all in about a half hour and charge you $20. Ah-the old days! Those shops are long gone. I assume there is zero interaction between the heater plumbing and the AC plumbing, but please correct me if i'm missing something. The zero loss of pressure during testing had me confused, but i'm now getting a few drops day and a leak is a leak, right? Just had the dash out, but from your helpful picture it appears i may not have to pull it again. If i do at least the how-to steps are fresh in my mind!

 

[Old Guy]

Cooling system pressure tests are not very good at detecting really small leaks, particularly at a wimpy 16 psi test pressure. if you have a significant volume of air in the cooling system expansion tank during the pressure test and you are losing 5ml or less of coolant during a 24 hr pressure test you will not see any significant drop in the test pressure. You can try and make the test work better by filling the expansion tank to the brim to try and eliminate the air cushion and then pressurize the system and watch for pressure drop. You can also crank the test pressure way up to increase the leak flow rate which will then show a faster pressure drop; but, that comes with a different set of risks.

If you want to be certain that this is a coolant leak, presumably from the heater core, I would dump some UV dye in the coolant, drive around some with the heater operating to get the dye mixed and into the heater core and then let the car sit and leak some of the fluid out. Check the leaked fluid with a UV light and 'if it glows you knows'. You may be able to poke around with the light to determine whether the leak is external to the heater core and just happens to be draining at the same spot.

 

[Honcho]

Good advice from Old Guy here. The AC evap and heater core are separate systems entirely, but they share the drip tray at the bottom of the HVAC unit. It connects to the black rubber hose Kaz indicated in his picture. The hose is meant for A/C condensation drainage, which is why you see a puddle of water under the car in the summer when running AC. However, if the heater core is leaking, any coolant will make its way down to the drain pan and exit the same hose. I believe you can still buy a new core from Honda. As Kaz mentioned, the new ones are aluminum instead of brass and the parts catalog will say they don't fit the earlier cars, but they do.

Part number is: 79110-SL0-A03

 

[TANTO]

I can be a little slow. My coolant is BLUE, my leak is YELLOW-GREEN. Duh – this now looks like an evaporator leak. I forgot that at my last R-12 addition having leak detection fluid added. I re-checked my AC just now and while it is working, it is weak. Problem solved i think. Moderator - feel free to rename thread to “fluid coming from hvac box drain” or whatever appropriate. I’ll now get on to finding all the parts/seals required to freshen up the whole AC system. Thanks!

 

[TANTO]

Joe's userID is @nsxspdfreak.
'Mention' feature may not work (never worked for me so no notification received) so search the userID and send conversation.

RHD model so different configuration from LHD but you'll get the idea.

What year model?
Heater core on early models is in brass.
Later one or OEM replacement in aluminium.
You can check the material by looking at the 2 pipes at the front bulk head.

What the colour of your coolant?
Type 2 is Blue but some Honda/Acura garages use green.

Do you have leak detector green dye in your a/c refrigerant?
When was the last time you checked the a/c refrigerant pressure?
You can do quick check at the sight glass on the a/c receiver/drier.

Kaz

Can't find Joe anywhere. Not under member name, user ID or combination and a conversation will not accept him as recipient. Can some one try it for me to see if this is ME issue or he left the room? Or anyone have an email or phone no please?

 

[Honcho]

Can't find Joe anywhere. Not under member name, user ID or combination and a conversation will not accept him as recipient. Can some one try it for me to see if this is ME issue or he left the room? Or anyone have an email or phone no please?

Try him at 239-6(nine)9-(seven)(eight)00

 

[Old Guy]

Different problem, same agony because the dash is coming apart to access the HVAC. The up side is that if you can put up with no AC you can still drive the car. The low AC pressure switch should prevent the compressor from running; but, I would disconnect the clutch control wire just to be sure.

Planning ahead! The HVAC box with the heater core is coming out to replace the evaporator so you are going to be into a cooling system purge and top up. If the cooling system hoses have not been serviced on the car this might be a good time since the vehicle will be out of service for a while.

 

[TANTO]

I see evaporators are available for 93 up, mines a 92. Will the newer model work? For the planning ahead, I assume my hard lines should be good and i'll only have to do the rubbers? I've already done most all hoses, but of course i didn't want to mess with a working AC system. I did purchase 30lbs of the 12 back when it was cheap so i'll want to stay on the 12. Thanks so much!

 

[Honcho]

I see evaporators are available for 93 up, mines a 92. Will the newer model work? For the planning ahead, I assume my hard lines should be good and i'll only have to do the rubbers? I've already done most all hoses, but of course i didn't want to mess with a working AC system. I did purchase 30lbs of the 12 back when it was cheap so i'll want to stay on the 12. Thanks so much!

Newer model will work fine- it's for R134a, which is why it's a 93+ part. 91-92 evaps are R12. TBH, I just sent my entire unit to Joe and he completely cleaned and refurbished it, including a new evap and expansion valve. Best money I ever spent.

 

[drew]

The newer evap and seals will work with R12 just fine.

The oil compatibility is the only thing that is of concern. If the evap is dry then just add in more mineral oil. If ester, then you can mix or clear out evap. PAG doesn't mix, must clear evap completely.

A brand new evap box might be most cost effective overall.

Check for "black death" which indicates a dying compressor. If the compressor needs to be replaced, then I recommend get the Legend version, it is the same body but with a higher displacement.

 

[TANTO]

Already had a new evap, heater core and compressor hoses coming from ATR before i heard about Joe G but i will certainly contact him for a seal kit or more. I've had comptect headers for most of the cars life and as i recall they come worryingly close to the compressor so thanks drew for the legend tip as i should likely replace the compressor as well. My local AC folks refuse to use my own R-12(argh), so not sure if i will invest in a vaccum pump and do this myself or what. While i pride myself of doing everything myself, after long past overcharging a second car with those little cans, i learned to have that done for me as they have the catch tanks. But since i have the R12 and manifolds i may dive in myself. Of course i likely will wait until the season is over as i really like to look at my dash right where it is he-he. Not to discourage anyone from a dash removal as it is really easy compared to other cars. I'm thinking this car DID take unput from the mechanics during the design process. Makes working on these babies "almost" fun.

 

[drew]

Cheaper, faster, and easier to buy a vacuum pump and just do it all yourself.

I got a MVAC cert a long while back because I was stunned at the cost of service for A/C.

I've also gotten lazy and on commuter cars as I just inject refrigerant without even pulling a vacuum. Works just for the life of the vehicle, though not recommended due long term moisture issues. Did ya know that one could inject propane and kinda works too?

 

[TANTO]

Embarrassed to ask this, but I can’t figure out how to disconnect the top portion of the AC compressor wire. I “think” I know how to get the lower portion of the connector off the oil stick bracket which I know will have to come out, but I first have to get the top connector off. Is this “pinch to release” or “pry” to release? Second question - I am replacing the evap and the compressor(legend as suggested) and have new flex hoses for the compressor end. I have purchased all the new o-rings for the entire system that I could see on the parts lists so should I replace the condenser o-rings also? I have the Joe G foam seal kit coming. I have low miles and have no indication of leaks up front, but of course now would be time to cover all the bases. Am I missing anything? My drier should be good, right? Should that green leak stuff be flushed out? Thanks!

 

[TANTO]

I just did discover the method to release the upper AC compressor elec connector. Sorry i need to pause a bit before i bother the the group. Since it appears almost impossible to release this push type connector by hand, i tried using a very long medium screwdriver from the bottom placed right on the push tab and pushed upward as well and it popped. Never done this on a connector and have no idea if Honda envisioned it, but it's done, compressor removed.