HamadUP

Hi,

I woke up this morning and I felt I am brave enough to remove my evaporator box. I said "brave" because every post here that talks about removing evaporator box contains words like "something you wont do again" , "PITA" , "hard to reach bolts" , "you need to remove your engine first!" .... etc.

My mechanical skills is a little below average, so if I can do it, your 10 years old son can do it. It took exactly 30 min. to completely remove the evaporator box, you just have to look for the best access for bolts and use the correct tool to do it.

First, I removed the wiper door actuator, then I removed the side louver vent, its very handy to have that access to side bolts, I removed and installed A/C blower motor assembly in 10 or 15 minutes by accessing through that vent. From there I unbolted the 4 bolts that hold the 2 halfs togther as seen in these pics :








then I removed the upper 2 bolts :




There is a small bolt that holds the box to the firewall in the lower driver side corner, you need to crawl under the car to unbolt it, thats where it is :




then you have to remove the upper firewall bolt :



and also remove the lower right hand bolt inside the cabin :





Now the box is completely unhooked to the car, pry it out gently from the blower housing then pry it from the firewall and try to clear it from anything that may hold it and left it up.

If you feel that the box is stopped by somthing and preventing it from being left up (thats what happened to me) then its most likely a steel duct coming from the inside of the cabin, you just unbolt the other 2 bolts inside the cabin that holds the heater core housing and then untighten the bolt on the stud that holds the upper side of the evaporator then pull the heater core housing inside the cabin just a little to clear the way. as in this pic :




Th shock was when I found that my box was cracked and someone tried to patch it in a bad way! Now I knew why I kept having hot air coming the A/C vents no matter what I do! :



I will remove that steel patch and will try to fix it with a fiberglass patch and then paint it the original factory color.

I think the evaporator core is the original factory one :



Look at all the dirt and detoriated seals on the ground! :






Thats it for now, I will go back and carry on fixing the cracked box.


Hamad

TopGunn

That's a very nice writeup and pictures, it's gonna be very helpful!

Thanks for posting.

ajrothm

VERY NICE WRITE UP!!!!!

Those pics will help out a lot of people. Good work HAMADUP.

Now is a good time to pull your AC box on the inside and make sure the doors seal off well and open and close off fully.

BTW you can buy those evap boxes from Doc Rebuild if you don't want to mess with fixing that hunk.

ajrothm

ALSO, make sure when you reassemble everything, that you seal ALL the duct junctions with good tape/sealer. I did the easy ones like the driver and passenger ducts but did not do the main duct from the ac box or the defroster duct. Now I can't get to them but I feel all kinds of air leaking out behind the dash when the AC is on and that air should be coming through the ducts.

Also a good time to install the C4 blower

SIXFOOTER

Very Nice Job, I wish I had done that on mine when I took it apart. You didn't have near as much crap in yours as was in mine! I agree with Aj, go ahead and fis the duct door seals whilt its all apart, only do it once. Also, from a writeup in here a couple weeks ago, I think it was from Photovett, Get some Lizardskin and paint the outside of the evap box and the firewall while its apart. From the tech data I read that is very good stuff and it will stop the heat transfer thru the evap box itself. Also it will be some more work, but cutting and fiberglassing in a C4 fan at this time would give you quite a lot more air flow.

Good Job

TopGunn

I've been thru this exercise too, someone told me the space between the duct and the defroster is supposed to be there by design but I don't recall the exact reason.

HamadUP

Thanks guys for the nice words.

Ajrothm, I just ordered the complete seal kit and I will give it most of my effort. I dont want to waste any bit of cool air. I dont think I will buy a new box because its very expensive (around $400) I need to fix mine, and I will try to fix it the best way I can. I will not pay great attention to how it will look because I plan to wrap the whole box with reflectix. I am not sure about getting a C4 blower instead of the original, do they have the same bolt pattern? I know the C4 is 1 inch or so thicker.

SIXFOOTER, I wish I can get a lizardskin or something similar here locally, I asked about it in several auto shops but they dont have any idea about it. anyway I will use reflectix sheet to cover the box and I will try to cover the firewall as much as I can. I hope Reflectix will withstand the engine bay atmosphere.

Tomorrow I will take the evaporator core and the compressor to auto A/C shop to test them for leaks. hope they will do fine. Then I will just wait for the new condenser, POA and expansion valves and hoses to arrive to start installation.

Hamad

78anniversary

I need to do this on my '78, did they change much between 71 and 78? Is it pretty much the same job as what is shown here?

HamadUP

I have no idea about '78 A/C. I know that the evaporator core is different as well as the compressor and valve system. I think the remove/install process is just similar. Again, I am not sure, maybe a '78 owner could chime in.

Hamad

Patrick73

I do not think that Reflectix will take the heat of the engine compartment; It was not designed for that type of usage in an engine compartment. (It does work great under the interior carpet).

You need to use a product designed for that type of application. I would suggest either a Thermo-Tec or Cool and Quiet product. Both are good. Both make an adhesive back heat barrier that will reflect temperatures in excess of 2000 degrees F.

Check out www.thermotec.com or www.coolandquiet.com

I personally prefer cool and quiet. Easy to cut and to apply. I have installed it on the lower firewall in my engine compartment, the two lower metal heat shields, and on the trans tunnel. It works great!!

And your photos and work description on this project are excellent! And Yes, Doha is HOT. I have been there a few times. You need to use every heat reduction and AC improvement available!

shafrs3

Oh I don't know about that, I'd say you have some good skills.

And your pictorial and documentation is very good..

ajrothm

Hamad,

You can get by fine with the stock blower if its still running well.. The C4 blower gives you a lot more flow but the problem is, the faster you push the air through the evaporator, the less cool it is. I RARELY use the high speed in mine except for when I first get in the car and its really hot. The reason is, I lose about 5* of cooling going from the 3rd speed(med) to HIGH speed. My AC will not get below 49* with the blower on high, yet will run 43-45* at medium speed. I checked this this afternoon with my new digital vent thermometer. 88* ambient.

The key is to get every bit of air flow through the ducts and out the vents AFTER the evaporator... That way you can run the fan on lower speeds but still have good flow out the ducts..

Definetly tape up all the ducts, even if you put new seals in, especially the main duct that has the one screw that screws into the ac box... There is a big lip that fits in the duct from the box there this is still a big gap there. I didn't tape that one and I feel all kinds of cold air coming out of it. Also check all grommets in the firewall...I thought I had all mine in and this last weekend, I noticed one on the left side of the distributor I could see daylight through....gotta plug that $hit.

mrvette

Yeh, I was going to say, ain't a thing the matter with his mechanical skills, did a good job....and YES on that documentation...

HamadUP

Patrick, yeah I was in a doupt about using the reflectix inside engine compartment. I checked both websites you mentioned and I liked the cool and quiet more, so I went ahead and ordered two 42" X 48" sheets of zeroclearance for that matter. I got two rolls of reflectix which I will use for inside cabin heat insulation and I thought maybe I could use the excess for firewall. Thanks for the advice, the zeroclearnce product looks very effective, lets hope it will defeat Doha's heat! BTW, did you mention that its a self adhesive sheet? I didnt read anything about that in their website. Will you come here again soon? please let me know so we can meet at some place if you wish.

Ajrothm, I dont think I will upgrade my blower, I think it blows enough air for a small cabin like the Corvette's. The behind dash work is huge for me, and I will leave after finishing the A/C work under hood.

shafrs3 and mrvette, thanks for the kind words

Patrick73

Hamad,
Yes, zero clearance is self adhesive. Very easy to install. I make a pattern, then lay it on the zero clearance, trace the pattern and then cut it with scissors. Lexus uses this same product on their vehicles. It really is effective at blocking out radiant heat.

ajrothm

Last night I drove my car to a show with the AC off, I was getting 98.5* heat coming through the ducts and it was only about 80* outside. Even the plastic air ducts were really hot, yet the floor and kick panels were relatively cool. No doubt hot engine air is getting into the AC system, so where the hell is it coming in from?

Only place I can think off is its coming in from the evap box, either through the seals or the box itself. I mean, how else does air get into the air ducts if the blower is off? especially with the plenum door shut?


Guess I need to order up my Zero Clearance and start insulating...

shafrs3

From a cracked evap box like shown in the pics above and or deteriorated foam seals that surround the evaporator pipes.

Here is a tech tip on cockpit heat:

https://www.corvetteforum.com/techti...=241&TopicID=3

HamadUP

Ajrothm, even if your evaporator box is not cracked as mine, the seals most likely they are very dry and getting engine hot air inside. When I removed mine, the seals were so dry that they just fall apart while pulling the box up from engine bay, the lower expansion valve side seal had a a visible cracks that will allow air go inside. Also the the seals between the box and the firewall were dried out and all gone. The engine bay is pressurized with hot air from the cooling fan so hot air will just go through any crack it will find.

Hamad

HamadUP

see what the lower seal looked like, enough to let alot of hot air inside your ducts :

TopGunn

If air was getting into the duct from the engine compartment it would most likely smell of exhaust fumes. If you don't smell anything then it's most likely being transferred from the hot engine compartment thru the heater/AC box in the engine compartment. Here's a couple of pictures after a drive on a hot day last year. One is from the exhaust manifold 1/2 ich away from the heater/ac box and the other is from the box itself. If the outside of the box is 240 deg then any air inside the ductwork in the car will heat up from it. Any slight amount of air getting by the seals will pass thru the ducts and get heated just like a furnace!