KahnBB6

iTrader: (5)

My SC300's A/C expansion valve has gone mostly bad and needs to be replaced now. It's going to be a big job and I'm opting to do it myself for reasons of cost and also because I've removed the dash before and don't want to risk anything fragile being broken during the process.

My evap core isn't leaking (yet) to my knowledge but it's a no brainer to replace it while doing this. The A/C system is holding for the moment but will be evacuated of freon just before getting into disassembly. I'm going to temporarily remove the clutch relay fuse at that time as well.

I have a new OEM expansion valve, new Denso evaporator core and I'm thinking it's a good idea to buy an OEM heater core as well since it's 22 years old. Overkill? For anyone who has done this, are there any other small parts I need to pick up just to make sure I'm not missing anything when I'm into it?

I'm going to use this DIY guide:

https://www.clublexus.com/forums/sc-...-56k-nono.html

And there is this small thread on Soarercentral on the evap core topic:

http://soarercentral.com/sc-forum/me...80/331625.html

Thanks all. I am not looking forward to this and while I have removed the dash once before it has been a while. I just don't want to have forgotten a grommet or seal once I've stripped everything out.

Sc400NL

i replaced my my evaporator a few weeks ago and it took me 4 hours to do , its pretty straight forward if you use the Lexus repair manual , hardest part is to unbolt and bolt the lines from the engine bay to the interior

i only replaced the evap and not the valve since my local AC specialist told me that those exp valves last forever and he never seen a broken one



here you see the evap with the valve on the right

just remove your glove-box and slowly work yourself in to the evap
remove steering,trac and cooling ecu




its easier then you might think

and yes , replacing the heater core seems overkill to me if you heater works fine

hope this helps

remove the airbox

KahnBB6

iTrader: (5)

SC400NL, thank you!!

So the whole dash does not have to come out to do just the evap core and expansion valve? That's quite a big difference. In my case the car's expansion valve isn't working correctly and is stuck mostly closed causing a high pressure issue (A/C system is at 350psi but should be at 250psi).

Are the two ends of the metal wires from the expansion valve accessible without the rest of that box (and the dash) removed? Looks like it but thought I'd ask to be sure.

KahnBB6

iTrader: (5)

Did some scouring on Soarer forums and found this:

http://soarercentral.com/sc-forum/me...80/357466.html

It's reversed of course but shows pretty much the same thing as with your pictures, SC400NL. So the dash doesn't come out and it looks like the expansion valve's metal wires/probes are tied to the piping that comes out with the evaporator core. Now I see what you meant regarding the firewall connection(s).

I didn't locate this thread before posting but thought I'd add it here for informational value (no pictures):

https://www.clublexus.com/forums/per...placement.html

Seems it involves this order:

-Get A/C purged at a shop
-disconnect battery (and wait 2 minutes for airbag capacitors to fully discharge)
-dismantle ONLY passenger side glove box (as shown above) and possibly remove the passenger airbag for 93+
-unbolt sensors and air box cover (many steps to that)
-remove screws for the evap connection at the firewall on passenger side of the engine bay.
-remove old evap unit and expansion/txv valve
-retain metal pipe between evap and txv + reconnect to new evap and new txv
-reinstallation is reverse (not sure of torque requirement of the firewall bolts)
-Take care to get recharged and possibly replace dryer unit inside the driver side bumper (to avoid moisture that may have been introduced)

Does this sound correct to everyone? I'm going to get into it very soon, just after I locate a new reman compressor to replace my current one which apparently has begun leaking after only one year of use

Sc400NL

here is a ghetto copy of the description i used

In the first sheet it says remove the ABS actuator but don't worry you don't have too
remove the charcoal canister so you can reach the 2 bolts that hold the AC lines at the firewall










hope this helps
1 side note ...i didn't replace my valve so i'm not entirely sure how to unbolt that , could be under the ABS lines , but you will see

KahnBB6

iTrader: (5)

It absolutely does, thank you! I was looking for that in the TSRM and hadn't found it yet. Yes, the coolant lines are near the ABS unit on the passenger side of the engine compartment near (lower than) the heater control valve. The torque specs on those are what I need to dig out from the manual.

This is amazing, though, thank you!!

Sc400NL

you welcome , glad to help

KahnBB6

iTrader: (5)

Small Addition to this. I found that Denso makes a replacement A/C thermal expansion valve replacement for our cars for about $55 or so. I assume this is pretty much the same thing we'd get from Lexus.

It is listed as #DEN475-0106 on their company website if you search for your year SC.

TXMAG

iTrader: (1)

out of curiosity, are you still running R12 or has your system been converted to run R134a?

KahnBB6

iTrader: (5)

R134A. The previous owner had it converted at a Lexus dealer years before I bought it.

TXMAG

iTrader: (1)

Did they actually change out parts like the condenser, compressor, evaporator, etc. or just change the seals/fittings? I'm debating on paying a lot to recharge with R12 (if I can find someone to do it) or potentially retrofitting modern style R134a system components and basically building a new AC system. I just haven't had great success in the past using R12 components with a converted R134a system. Thoughts?

KahnBB6

iTrader: (5)

To the best of my knowledge it was fully converted to 134A, yes. The records show it being done at a Lexus dealer sometime in the late 1990's. I don't remember the date. The car would have still been very, very new then. No idea why someone would pay extra at the time to convert the entire system but that's what happened. Maybe it had something to do with it being a California car.

Since buying the car I've replaced everything all over again: new R134A compressor, front condenser, evap core, tx-valve, Drier, and some line cleaning to clear out contamination from a bad Denso Drier. One of the most expensive headaches I've had this year, I assure you.

I'm no expert on A/C systems. The last time I had an R12 car was with a classic Ford some sixteen years ago. Even then it looked daunting to buy a full kit to convert it to R134A. At the time I just used more R12 and had it serviced.

These days I'd probably convert a car to R134A.... *IF* there already were some major component issue or system failure that would require I pay a lot anyway. But R12 is expensive and rare to begin with by now.

Other than all the major components I do not know what lines, etc would need to be changed. I assumed it had to do with the service connectors, pressure fittings, O-rings, lubricating fluid and such. Again though, A/C is not something I'm well versed in.

But Lexus did convert some of these early cars at the dealerships years ago.

t2d2

iTrader: (8)

That's the first I've heard of a SC being equipped with R12 after '92. Weird. Maybe your '93 was a '92 build date and there was some overlap there in how things were handled?

KahnBB6

iTrader: (5)

It was. 10/1992 if I recall. So maybe R12 was a 1992-1993 quirk only. Like 1992's being the only year without a pass airbag.

TXMAG

iTrader: (1)

Great info, thanks Kahn.