Da Mail Man

**NOTE: replies from me in caps are NOT yelling and only serve to segregate portions of the conversation.

Greetings all,
I knew it would one day become inevitable - the evaporator in my 1988 coup is leaking.

Found oily residue on my black rubber mats twice already. The first time I shrugged it of but, vowed to keep an eye on it. Scrubbed them perfectly clean and reinstalled them. Three weeks ago found that mysterious "sheen" back on them (thank god they are over sized so my carpets aren't ruined). So, took my ac leak detector "sniffer" and inserted into the vents and heater outputs of the car and it lit off...Can we all say "MF!!"?

So, years ago I read a post or two on here about accessing the EVAPORATOR and two different ways to do it.

I have seen some net picts today showing the ENGINE SIDE (not cockpit) enclosure exposed revealing the evaporator but, no directions as to how the service person got to that point.

Most of the picts or links I have seen are to access the heater core and, some requiring the removal of the passenger seat which I am not a fan of.

So -

Is there a posted guide for "splitting the engine side of the heater/evaporator box as I cannot locate same....Thanks again for ANY assistance.

Cliff Harris

That makes no sense. The evaporator is filled with FREON, which would just evaporate if it leaked out.

Your HEATER CORE is leaking.

Da Mail Man

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Thanks for the reply. WHY doesn't that make sense? So, you are telling me that my leak detector picks up ethylene-glycol and water now which it is not designed to do? Not possible here.

I am HVAC certified with universal ticket for 30 years. The car uses R-12 refrigerant and that refrigerant has O-I-L (OIL) in it. When refrigerant leaks, along with the gas comes oil.

When you look at refrigeration systems that are mal-functioning, besides looking at gauges, etc., one looks at the "piping" joints and braze fittings (where applicable) and looks for an oily residue.

Have you ever seen a connection where an ac hose connects to an accumulator, compressor, or condenser and notice an "oily dirt" there? That is the refrigerant (freon) oil and the dirt is from the road, etc that sticks to it.

Why oily residue you ask? It is as i said above. (see: at elapsed time approx 4:00). Refrigerant carries oil. Where the refrigerant goes so does the oil, where the leak is, so is the oil that is left behind with the gas escaping to atmosphere.

Cars' cooling system is not loosing coolant but, the a/c system is. I seldom drive the car and only start it 2x's a week and let it run for 15 minutes so, no pressure on the cooling system. At the same time i run my ac regardless of ambient temp.

I have extracted the R-12 from my system with my recovery machine and had fixed a loose joint (o-ring) at the condenser joint and that is when I noticed the oil (not coolant) glistening on my mats. The "sniffer" lit off in my ac duct-work, a sniffer designed for refrigerant will NOT pick up coolant, etc.

357L98

The evaporator is entirely under the hood, and if it was leaking oil, the oil would come out of the drain hole and leak out in the same place as the condensate water. I'm not sure what could be getting on your mats.

Da Mail Man

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Thanks for the reply. NOT TRUE in part.

Since the air in the cockpit of the vehicle has to recirculate (via forced air fan) and pass over the evaporator to do the heat exchange and get cooled and then RE-ENTER the cockpit (via the vents, duct-work), there MUST be an opening (for lack of a better phrase) between the cockpit of the vehicle and the evaporator. Lets not confuse the function of the blend door underneath which directs air flow.

There is and has been NO LOSS of coolant and levels remain the same. Yes, there is a condensate drain hole in the evap/heater housing but, lets remember, the car is sitting and coolant is NOT under pressure while the refrigerant IS which will provide a mist of refrigerant and slightly add increased pressure to the housing and like i said, the leak detector picked it up in all my vents, upper dash included. Therein qualifies the access to the cockpit, the evaporator, the loss of refrigerant (via gauges) and the oil found on the mats.

Da Mail Man

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Thanks for the reply.

The evaporator is entirely under the hood,
OK, STIPULATED

and if it was leaking oil,
IT IS AS BEING VERIFIED BY RESIDUE AND BY LEAK DETECTOR THAT DETECTS REFRIGERANT LEAKS.

the oil would come out of the drain hole and leak out in the same place as the condensate water.
NOT TOTALLY TRUE! There is and has been NO LOSS of coolant and levels remain the same. Yes, there is a condensate drain hole in the evap/heater housing but, lets remember, the car is sitting and coolant is NOT under pressure (PRESSURE RELIEVED BY UNDOING THE CAP BEFORE PARKING/STORING CAR) while the refrigerant IS which will provide a mist of refrigerant and slightly add increased pressure to the housing and like i said, the leak detector picked it up in all my vents, upper dash included.

I'm not sure what could be getting on your mats.
REFRIGERANT OIL

357L98

I'm sure if the evaporator is leaking refrigerant, you could detect it inside the car, since it is a gas. But, oil being a liquid it would only be able to drip into the bottom of the evaporator housing. So, I still can't see how oil is getting from under the hood to inside the car. I am only trying to understand your problem and give some help.

Da Mail Man

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I'm sure if the evaporator is leaking refrigerant, you could detect it inside the car, since it is a gas.
YES, IT IS.

But, oil being a liquid it would only be able to drip into the bottom of the evaporator housing.
NOT ALTOGETHER TRUE. THE REFRIGERANT IS UNDER PRESSURE. THE GAS AND OIL MIXED TOGETHER FORMING THE REFRIGERANT IS DISCHARGED (LEAKS) THROUGH THE LEAK SITE AND SINCE IT IS UNDER PRESSURE AND A FINE MIST, THE OIL JUST DOES NOT LEAK TO THE HOLE AND DROP IMMEDIATELY TO THE "GROUND", IT IS "PROJECTED" UNDER PRESSURE MUCH LIKE A WINDEX BOTTLE EXPELLING IT'S LIQUID. THE REFRIGERANT IN THIS CASE IS FORCED OUT AND IS CARRIED UNTIL IT CONTACTS A SURFACE AND THEN COULD DROP/RUN. MY RUG(S) ARE DRY (OVER AND UNDER) DUE TO MY OVER-SIZED MATS (SEE: POST #6 IN THIS LINK, https://www.corvetteforum.com/forums...or-1988-a.html ) THINK OF IT AS "FOG" OUTSIDE AND THEREFORE IS DETECTED BY THE LEAK DETECTOR. ONE MUST ASK HOW CAN A LEAK DETECTOR DESIGNED FOR REFRIGERANT ONLY, PICK UP/DETECT COOLANT?

So, I still can't see how oil is getting from under the hood to inside the car.
IS IS ALL CONTAINED IN THE SAME HOUSING WHICH, PART OF THE HOUSING IS IN THE ENGINE COMPARTMENT AND THE OTHER IN THE COCKPIT!

I am only trying to understand your problem and give some help.
I SEE THAT AND THANKS BUT, IF THE HEATER CORE AND EVAPORATOR ARE LOCATED IN THE SAME CONTAINMENT, THEN EITHER COULD FIND IT'S WAY TO THE COCKPIT.

WITH;

(1) THE COOLANT LEVEL REMAINING THE SAME AND,

(2) THE REFRIGERANT "LEVEL" DROPPING OVER TIME AND ,

(3) WITH THE LEAK DETECTOR GOING OFF IN ALL MY VENTS/DUCTS, IT IS OBVIOUS AS TO WHAT IS LEAKING AND WHERE.

WHAT I AM LOOKING FOR AS INDICATED IN MY ORIGINAL POST ARE DIRECTIONS AND POSSIBLY PICTS TO ACCESS OR TO SEE IF I CAN ACCESS THE EVAPORATOR VIA ENGINE COMPARTMENT AND IF NOT, THE INTERIOR PASSENGER COMPARTMENT.

357L98

I understand what you mean. The way I see it, the heater core is inside the cabin and the the evaporator is outside, but since they share ducting either could present some leakage inside the car.

As for your original question about removing the evaporator, you would remove the box half section closest to the engine by taking out the screws/ nuts on the firewall. Then remove the big screws holding the two case halves together, and pull them apart. The core should remain in the passenger side of the case, just pull it out. Hoses removed first, of course.

Da Mail Man

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If the rugs were wet then, I would have my answer straight up but, with the rugs dry and the leak detector going off, the writing is on the wall. Do you know of a procedural text or picts of this being done as I cannot seem to find one.

Da Mail Man

............Anyone?....nobody has dismantled their heater/ac box before?

WVZR-1

The procedure in this link should work for all C4 evaporator removals. You might modify somewhat but it looks quite straight forward. I'm quite sure it's been mentioned by many through the years.

https://www.corvetteforum.com/forums...-and-pics.html

Da Mail Man

Ok....

Started evaporator removal today and "ALMOST" finished the removal of the case 51/2 hrs later!...UGH!.

Most of the procedure was not that bad BUT, getting the case screws out is and still remains a B-tch!...... Facing the car, a "case-to-firewall" screw at the extreme lower right hand side (nearest the engine) is almost impossible to get out due to the exhaust and other "barricades".

I had to go out and buy another 1/4'' drive ratchet to try because mine was "loose" and has seen better days. That was a waste of time. Wound up using a slim but long snap-on 10mm wrench with about 2000 32nd'' inch cranks of the wrench to get the screw out. Have no idea as to how I am going to put it in!

I have the upper section of the case split with the lower part still sticking together. I suspect that it is because this most likely has not been opened since date of manufacture. I quit for the day as my back was giving out.

I have no idea as to what I will find when I split the case but, I DO know it (evaporator) is leaking. When I reassemble the system and replace o-rings and orifice tube, I will have to pump it down (vacuum) for a few hrs and see if vacuum holds for a length of time. There was someone whom had a pict of case split with evap still inside but, cannot find it.

PatternDayTrader

Dang just one year later .... You really got right on top of this one.
Heres a pic of a 95 car ...

PatternDayTrader

Make sure you install the water screen on the new evap core and make sure you seal all the gaps between the body of the core and the case halves so no air can pass around the core.. If you don't then expect a performance difference of about 20 degrees.

As labeled above, that picture is from a 95 model car, so its probably not exactly the same as yours but should be similar.

Da Mail Man

Feakin' awesommmmm !

Did you have difficulty separating the case like I am having?...I just noticed but, my helms says to take off the drivers side of case.

PatternDayTrader

There are two or three bolts down there holding the case halves together.
I got them out from underneath the car, and they have to come out.
This is also a good time to replace the fuel filter by the way.

Use strip caulk to seal the case halves back together when you reassemble everything.

PatternDayTrader

I did not remove the drivers side case half.
My car is a 95 so its not impossible that's your is different but I really doubt it.

Da Mail Man

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Thanks for the reply...I just followed the manual. It would appear that the passenger (r) side should be easier but, like I said - the manual.....I have it split and believe I have all the screws out...Will contend with that later today...Have a pict or two at the start of this but, have to upload.....Ok, back in a few hrs!

Da Mail Man

OK.......here it is...Had to quit for today - intermittent rain.
It was like pulling teeth without Novocaine!

I see a screen attached to old evap.




Going to attempt to use it and affix by adhesive caulk along contact edges then, apply more caulk down through the non-contact side to "meet up" with caulked perimeter so it will "grab on".

Would use tie wraps but, if they become brittle , they may "spring" open and cause some issues. Pardon the leaves in the "wiper tray" as they accumulated over 2 weeks - the rest I don't know how they got by the wiper tray area as screen is intact....Will affix a smaller screen when done.
Drivers side of evap case pulled away



case obstruction from exhaust
Old evap and filter/drip screen