Mustang5L5’s progress thread - Rear window fun

FastDriver · Jun 19, 2026

Or overfilled, and doesn't hit the pop-limit in cold weather. Also, these liquid lines today are often not to proper spec. They are often too restrictive. Confirmed this with a couple of folks who spend a LOT of time on foxes professionally.

I'm going to address this in Black Jack, where I have a measured pressure issue that looks like a clog, even when everything was brand new, and another airflow problem in the cab. I remember black jack's system being amazing. Now, it doesn't cover it in hot weather.

Mustang5L5 · Jun 19, 2026

But 3-4 years later? It wasn’t even that warm when this happened. I’ve driven on 95+ humid days without issue. I think it was barely 80 when this happened. I also filled by weight, and pretty sure I stayed towards the low end

Liquid line was an NOS piece. I have a 2nd NOS unit as well.

Maybe I’ll address it later this summer. I did some more driving and tuning today. Working on my startup from cold start( well 80 degrees) to hot restart. Also did some more driving and pulling fuel out of the top end of the VE table. It’s getting there. As you can imagine lots of adjustment to the top end being made.

Car drives pretty nice. Still a bit rough around the edges but it’s getting there.

85GTStangGuy · Jun 19, 2026

Mustang5L5 said:
....Need to source a new blowoff valve....

This it??

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FastDriver · Jun 20, 2026

Awesome. Yeah, those are valid reasons to doubt my guesses. Glad the tuning is getting there. Wish I had a NOS liquid line.

WhiteCobra95 · Jun 20, 2026

How does the A/C on these cars work? Is the pressure mechanically regulated or does the ECU cycle the compressor from a high pressure sensor? I've never had to work with these systems but it would be good to know. Any overview you can provide would be great. I've worked on modern cars with both variable compressors and cycling systems, but I don't know how they did it with EEC-IVs.

Mustang5L5 · Jun 20, 2026

There is no high pressure switch. It’s a mechanical relief valve. When you get over 450psi it just vents.

However looks like the relieve is not a one-time use thing if I’m holding pressure. Need to get my gauges on it and see how much exactly

FastDriver · Jun 20, 2026

Definitely not one time use.

Mustang5L5 · Jul 9, 2026

Well just to update. No pics

Been working on the tune. Having the right injector settings has made this easier I will say. But cold start is pretty sweet now. I have cold and hot starts from 80-185degrees pretty dialed in. Can't really work on 20-80 degree starts til fall/winter. I'll never drive the car in the winter, but I do have reason to start up and move it once in a while so i need to make a note to work on the tune at those temps.

Been doing short drives with auto-tune. As i suspected with the wrong injector settings, the VE table was leaner than needed at low RPM, and much higher than needed at load/higher RPM. So been slowly tweaking that. Car is pretty nice to drive. Not really much else to say. It starts up, doesn't stall, idles nicely and drives pretty smooth. Still need to tune accel enrich a tad (bucking when i jump on the gas a bit) but can't really do that until the VE table is fully dialed in, which i'm not ready to claim yet.

In other news, finally tracked down a local rear hatch glass that might have a good read defrost grid. Mine was destroyed years ago and my OCD wants an intact grid as i hate looking back and seeing the lines torn up. So if it tests out good, i'll polish it up, have it tinted (along with rear quarter windows) and slap it on.

Haven't looked at the AC yet. I've been mostly driving in the evening when it cools off anyway so hasn't been a need. I'm contemplating changing this out for R-134a if i have to discharge the system, which I think i do. I have to get a vacuum tank, pull a hard vac and reclaim my R12. Or at least that's the story i'm telling people

FastDriver · Jul 9, 2026

Mustang5L5 said:
In other news, finally tracked down a local rear hatch glass that might have a good read defrost grid. Mine was destroyed years ago and my OCD wants an intact grid as i hate looking back and seeing the lines torn up. So if it tests out good, i'll polish it up, have it tinted (along with rear quarter windows) and slap it on.

Haven't looked at the AC yet. I've been mostly driving in the evening when it cools off anyway so hasn't been a need. I'm contemplating changing this out for R-134a if i have to discharge the system, which I think i do. I have to get a vacuum tank, pull a hard vac and reclaim my R12. Or at least that's the story i'm telling people

R12 was awesome. I miss it, but early on Black Jack did amazingly well with R-134 until I screwed things up trying to learn A/C.

After the pickup truck hit me and crumpled the hatch a bit, I took an insurance pay out and started looking for a replacement hatch, rather than straightening and/or paying for paint. I was so fortunate that the one I eventually found came off of a car with great tint and working defrost. Black Jack has literally never had working defrost until this hatch. As an added bonus, it came off of a late 91 car with the later hatch striker. Now, it clasps easily and has no bushings on any striker, anymore. I had to replace a few of those a year.

Glad you've got most of the tuning finally ironed out. I remember your injector settings being my biggest concern when you first started, but doing it a few times is a great way to cement the concepts and see what it looks like when things are off. I haven't spent enough time with idle in heat like this. Mine does fine when A/C is off, but surges in hot weather with A/C on. Once you learn how to tune, I wonder if you ever get to a point where you really feel like you're done. Hasn't happened to me, yet.

Mustang5L5 · Jul 11, 2026

Welp. Hatch off an ‘87 Saleen is now with me.

Not sure if the defrost grid is good. Gonna remove the glass, test it out, polish it up, and if not acceptable I’ll just relist the glass and that’s that.

Mustang5L5 · Jul 11, 2026

Started cleaning it off. Glad is clean. Grid is iffy. Will need to test it and see. There is some blotching I’m not a fan of.

Gotta see how I can remove this.

Just noticed the window molding trim is still on this hatch. It’s in decent shape. I also looked up what these were selling for on eBay and holy wow.

Ordered the tools to try and pull the trim off and the glass off without damage. Wish my luck.

Wish this badge was still on the hatch for my wall collection

FastDriver · Jul 11, 2026

Man, I got lucky with mine after the accident.

Mustang5L5 · Monday at 7:59 AM

FastDriver said:
Man, I got lucky with mine after the accident.

All the hatches i see on Marketplace are junk. Rust, needs paint welding, etc. Still want $300-400+.

I managed to get the window trim off without bending it up. Gonna SEM trim black paint it and squirrel it away. Now to cut the glass out. Good thing it's gonna be 95-100 this week. Figure lay it out on the ground to heat up, and my window cutting tool should cruise through the butyl without much fuss

Noobz347 · Monday at 11:59 AM

Mustang5L5 said:
All the hatches i see on Marketplace are junk. Rust, needs paint welding, etc. Still want $300-400+.

I managed to get the window trim off without bending it up. Gonna SEM trim black paint it and squirrel it away. Now to cut the glass out. Good thing it's gonna be 95-100 this week. Figure lay it out on the ground to heat up, and my window cutting tool should cruise through the butyl without much fuss

If it's not a crazy amount of trouble: Record the glass removal if you can.

General karthief · Monday at 2:08 PM

Put tape at the defrost wire connections on each side of the glass for reference so you don't wreck the connections on the glass.
ask how I know.

Mustang5L5 · Monday at 2:49 PM

General karthief said:
Put tape at the defrost wire connections on each side of the glass for reference so you don't wreck the connections on the glass.
ask how I know.

That's my main concern here. The defrost. Because if i destroy it then all this is for nothing.

Plan was to chuck this in the sun for an hour or two and then cut it out carefully.

General karthief · Monday at 3:21 PM

Wire method or L shaped window tool?

Mustang5L5 · Monday at 9:12 PM

L-shape. Gonna give it a go tomorrow and see how it goes.

Mustang5L5 · Tuesday at 7:12 PM

Glass out. That was easy. Put it in the sun and the tool cut through it like butter. All of 5-10 mins to do.

Unfortunately now that I can work on the glass, I’m getting inconsistent readings on the defrost grid. Not sure it works well enough to my liking. Gonna borrow an infrared camera and put 12v to it and see what happens. But I think all the conductive paint bled out a bit too much and the grid has too many breaks

But this project might be over. Gonna clean it up and toss back on marketplace. What’s used hatch glass go for? I did all the hard work removing it. I know the hatch trim has value.

General karthief · Wednesday at 7:17 PM

I wonder too I got a rear glass no defrost I need to sell before it gets broken.

Mustang5L5’s progress thread - Rear window fun

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

Stangnet Facilities Maint Tech... Er... Janitor

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

wonder how much it would cost to ship you a pair

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