A/C system - how to remove the cooling unit, evaporator, expansion valve

alia176 · 07-29-09, 08:14 AM

It's summer and some of us are experiencing A/C troubles so I think it's time to do a writeup on how to remove the cooling unit, evaporator and expansion valve out of a '97 80 series.

Removal of the cooling unit is very straight forward, plan on about half hour and minimal cursing

You need to first evacuate the system of all refrigerant before starting this project unless of course the system is already empty to a leak somewhere

This is my third time removing the cooling unit so this is becoming old hat. I can remove the stupid thing in about 15 min.

If you're a big dude, it may help to remove the front pass seat out of the vehicle to allow for more work room

Tools needed:
long phillips screwdriver
10 mm socket (shallow and wobble)
12" ratchet extension
10 mm box end wrench/gear wrench

Safety:
- eye goggles. <== can't stress this one enough.
- good gloves to prevent frost bite
- Please be aware that this is a closed system and is capable of achieving very HIGH PRESSURE. So, use caution and common sense when opening up the system.

R134a is not toxic to the environment as R12 was but still, try not to breathe this stuff!

I'm going attach the pics to this thread rather than going through photobucket for a better long term picture storage solution. I may not have a photobucket account in the future!

There are couple of ways to detect A/C system leaks:

-using R134a with colored dye that can be detected using UV light and special glasses
-pressurize the system with compressed air (has moisture) or Nitrogen (no moisture) and then look for leaks using soap bubble test or listen for air escaping sound.

I use both the UV dye and the Nitrogen system to find leaks. I took a hose that came with a R134a kit and then cut it in half. Using some brass fittings and a schrader valve, a home brew hose connection was constructed so that external air/Nitrogen can be pumped into the A/C system using the Low pressure port at the compressor. The pressure is set to about 40 psi.

alia176 · 07-29-09, 08:15 AM

Pics of the Nitrogen tank.

alia176 · 07-29-09, 08:16 AM

Start by separating the two hard A/C lines at the firewall from the evaporator unit. The lines will be a little hard to remove since they've been there for a long time! It's a good idea to blow out this area with compressed air so that no dirt gets into the system. You need to be extra aware of not letting any contaminants get inside the A/C system.

If your system will be open for a long time, plug the A/C line holes with a rag or paper towel.

Second & third pic are of the glove box and speaker grill removed to access the glove box bottom metal brace. Hopefully the pic will speak for themselves from this point forward. This brace has LOTS of hardware so make sure to remove all of them . Pay particular attention to the hardware on the left side of the brace, where it meets up with the center dash area. There's a hidden phillips that you need to remove.

A 10mm socket and a phillips will do ya.

alia176 · 07-29-09, 08:17 AM

The first pic is of all the hardware that comes off after the removal of the glovebox, speaker grill and the metal brace.

Second pic is of the left side of the metal brace with all kinds of angles to hide the damn screw! When you remove the metal brace, the ECU will be a little loose and this helps in the removal of the black box on the next pic.

Third pic is of the removal of the black box doohickey using a single phillips.

To be continued....

alia176 · 07-29-09, 08:17 AM

Remove the black box by disconnecting the connector on top.

Then disconnect the white connectors on top of the cooling unit. These come apart fairly easily so be patient. Push the tab and pull apart the connectors.

Once the connectors are apart, you'll see some hardware that are in the back.

Atticus · 07-29-09, 08:18 AM

Subscribed.

alia176 · 07-29-09, 08:22 AM

Start my removing the front, medium height 10mm screw.

Then remove the top right nut.

Then remove the top left nut.

alia176 · 07-29-09, 08:23 AM

Remove the bottom right screw

Remove the bottom left screw

Remove the forward left screw using a 10 mm speed wrench or a box end wrench.

alia176 · 07-29-09, 08:30 AM

Another shot of the last screw. This should be all the hardware that needs to be removed.

Start by placing your left hand on top of the cooling unit and pivot the top away from the top two studs.

Then it almost falls out!

alia176 · 07-29-09, 08:38 AM

But not so fast, there's one last connector that needs to be disconnected

Voila, the cooling unit is almost out.

Don't forget about the drain hose!

alia176 · 07-29-09, 08:44 AM

Some pics from couple of days ago:

Pic of where the evap meets up with the hard A/C lines in the engine bay. To the right is the blower compartment where you'll find all sorts of debris and sometimes mouse nest!

Second pic is of the cooling unit as it sits in the vehicle.

Third pic shows the clips and phillips screws that keep the two halves together.

alia176 · 07-29-09, 08:47 AM

Before removing all the screws and clips, cut the foam at where the two halves meet up. This will preserve the foam pieces w/o tearing.

alia176 · 07-29-09, 08:57 AM

Remove the clips and screws then gently pry the two halves apart. Those clips can take off on you so be careful when removing them!

My evap needed serious cleaning!

alia176 · 07-29-09, 08:59 AM

And there is the expansion valve! It's held on with two allen bolts.

Two pics showing a new valve next to the old valve. I sure hope replacing this valve will make my vent temps stay cold!

alia176 · 07-29-09, 09:02 AM

Finally, two pics showing the removal of the A/C Dryer. This is a must if you're opening up the system and changing out the expansion valve.

Best access to the dryer is through the driver marker light. Tip: loosen the top two 10mm bolts first before opening up the bracket. These two bolts will very tight and will make the dryer move around on you unless it's still securely attached to the vehicle.

The FSM states to add 10 cc of PAG 46 oil to the compressor when replacing an expansion valve. Pay close attention to the FSM in regards to how much oil to add to the compressor when a A/C component has been replaced.

Well, that's all I got for now. Remember to re-install with brand new O rings by coating them with compressor oil first. These are metric O rings and not found in the typical auto stores unless special ordered.

I'll post up more pics of the evac and recharging process later today.

Thanks.

alia176 · 07-29-09, 09:07 AM

Some pics of the manifold gauge set hookup and the Robinair vacuum.

Buckru · 07-29-09, 09:08 AM

AWESOME. That right there is gonna do a lot of of people a lot of good.

Many thanks,

Buck

alia176 · 07-29-09, 09:08 AM

The FSM states to vaccum until -30 Hg has been acheived, then close both manifold gauge knobs and then sit for a while to see if the system can hold vacuum. Elevation play a role on what the low pressure gauge should be showing.

One thing to note: be sure that your gauges are calibrated! Both of mine were a little off so I adjusted them to show proper psi (little adj screw on the dial).

Blue = Low pressure
Red = High pressure

alia176 · 07-29-09, 09:09 AM

PIcs of the recharging process. In order to speed up the process, I'll submerge the freon can in a jar of warm water, while making sure that the can is upright.

alia176 · 07-29-09, 09:09 AM

Some numbers.

The Low and High pressure gauges are in the "normal" range based on the ambient temp at the house.

Vent temp is a cool 40°, sight glass shows "clear" and engine rpm is around 1200.

Well, that's about it folks - from start to finish over a couple of days. Hopefully, the mystery is solved for some of you wanting to do this project and save a little money.