Hello!

I recently bought a project C4 and found an issue with the wiring harness that we got fixed! (If anyone else encounters ECM fuse blowing randomly check your wiring loom to see that its not disintegrated. There is a metal bracket holding the harness that can slowly cut into wires when engine moves from transmission.) Now that the major problem is fixed I have a bunch of little things I have to do. Below is a list and if anyone has any advice please let me know! I am back in school now so after I graduate I should have much more time with the car so in the mean time I just want to get a shopping cart going so I can buy in a good sale.

For reference car is 83k miles and compression was equal on all cylinders. No rust at all was in Florida for all its life.

Mechanical Issues:
1. The front left brake line seems to be clogged? We replaced both front calipers, brake pads, and brake hoses. We originally thought it was a seized caliper since it was stuck closed and not releasing. We took out the caliper and cleaned the cylinders but even then it was still a struggle to get it back in. Something else we noticed is when we were bleeding the brakes that nothing gravity fed on front left but on front right it came out freely. When driving now and braking the car steers to the left a little. (I have new rotors but did not want to put it on since it will be sitting for 6 months). Not sure if brakes just need to settle but an observation we saw.
2. A lot of the different connectors disintegrated or broke when we had to take off everything to move the engine harness. Is there a handy kit for common connectors I can buy? I found https://www.summitracing.com/parts/cei-103005 but, not sure if this would be good enough.
3. The AC blows (Not hot or cold) and I get a code 01 on the C68 interface. I have seen online that sometimes this can be the blend motor door? Would anyone have advice on what to do or look at for this. It has some sort of freon in the system when we opened up the bleeder valve but, is there a way I can tell if it had the conversion done? The compressor clutch also never comes on.
4. I would also like to replace all the vacumn hoses since all of them seem to be original. Where did you guys get your replacements? I could not find a set online for the car.
5. The foam around all the vents in the car just disappear when you touch it. Where should I get replacment for these?
6. Where do you guys get your weather stripping. I have seen a variety of prices from like $100 to $500 and $1.2k.
7. There is also a crack in the windshield but I hope this is just something insurance will cover. Worse case where have you guys bought the windshields at to do yourself?

Cosmetic Issues:
1. Clear coat is peeling. Is this something as simple as sanding and applying another clear coat. Should I just sand it myself and go to MAACO for a clear coat or is it simple to do yourself. (The car is red if that means anything)
2. Seats are torn. I have seen a lot of reccomendations for Al Knoch but is something from Lseat also going to be decent? I dont want showroom quality but I still want the car to be nice.
3. I would like a glass top since I think the black top would look better with the Red. Where did you guys get yours at and are you still happy with it?

Things I would like to mod:
1. It would be nice to switch in a whole new exhaust system, and opt for long tube headers. What have you guys done to your C4s? I would most likely do these last or in parts since its not needed and I just want general experience doing it. If I were to do long tube headers first that would get rid of the cats right? What are the pros and cons for newer smaller headers with free flow cat vs long tube headers?
2. I would also like to add an alarm system or kill switch. What success have you guys had.
3. Potentially a manual swap for the fun of it. I know its more econmical to just buy a manual but I bought the car for a project and to learn.

Thanks for your help guys! I am still pretty novice when it comes to these things but have been loving the experience so far! I have been trying to use my other posts as a diary of a sort if anyone comes across issues I have. A lot of the post I have seen enquiring about parts is outdated a lot of times if it was before covid so its hard to get updated information.

 

A C-4 is the retirement home for electrical gremlins...

 

What year do you have? Since you replaced the flexible brake lines (correct?) Id start at the master cylinder and disconnect the line going to the caliper in question and see if there's any fluid flow at that point then work towards the caliper. If you have an 86 or newer you have ABS which may complicate things. Id be very hesitant about driving the car until this issue is resolved.

I would NOT install a kill switch or alarm system. You have plenty of other things to address. I have spent many hours undoing PO 's electrical work. C4 electrical system is complicated enough (to me).

Many have recommended Corvette Rubber for weatherstripping but note they are expensive. Be careful about buying cheap versions because many times they don't fit or they interfere with door closure etc.

 

Sorry, I didn't notice you posted the year in the title.

 

I am an electrical engineer for work so I was not too worried about electrical problems. I was more suprised I have not seen anyone talk about the engine harness bracket causing shorts before. After chasing it down I am pretty comfortable with all the electrical stuff on the car lol. I am just glad we were able to find it before I had to leave again for school. My dad is happy all that is left is mechanical issues as well.

Quote:
Originally Posted by ls777z
A C-4 is the retirement home for electrical gremlins...

 

Thanks! Yeah the next thing we were going to do is check out the metal brake line coming from the master cylinder. I really hope its not an issue with the ABS since its not spitting out any codes.

The kill switch/ alarm system would definetly be one of the last things I do when I get it running reliable and safe. The PO for our car bypassed the fuel pump, did a resistor bypass, and also hot wired the fans to always be on. We managed to undo everything except the resistor and it all seems to work fine so not sure why they did it in the first place. I assume it was an attempt to fix the ECM fuse popping maybe. According to the carfax it looked like they were chasing down that short we found for 5 years now. Its a little sad that the mechanics PO took the car too kept only replacing the ECM and charging them that as the "fix". (They replaced the ECM twice at that mechanic shop) If they ever took the time to open up any of the ECMs they would of seen it had no shorts on it so it had to of been engine harness or I/P harness.

I think I will end up with corvette rubber its just a tad bit sad to spend $1k+ on weather stripping lol. On my old accord it was less than $50 and still works great 5 years later.

Quote:
Originally Posted by pltmgr
"What year do you have? Since you replaced the flexible brake lines (correct?) Id start at the master cylinder and disconnect the line going to the caliper in question and see if there's any fluid flow at that point then work towards the caliper. If you have an 86 or newer you have ABS which may complicate things. Id be very hesitant about driving the car until this issue is resolved.

I would NOT install a kill switch or alarm system. You have plenty of other things to address. I have spent many hours undoing PO 's electrical work. C4 electrical system is complicated enough (to me).

Many have recommended Corvette Rubber for weatherstripping but note they are expensive. Be careful about buying cheap versions because many times they don't fit or they interfere with door closure etc."

 

Also yes I forget, yes I replaced the flexible brake lines.

 

A 90 is kind of its own beast. There are little things which are unique to it when compared to other C4 model years. Seems like the 90 and 91 model years were stuck in the middle of a transitional period.

Overall I've been happy with my '90. Though it took a few years to get it sorted from the previous owner's Mickey Mousery. Same thing, previous owner hacking the electrical up and stuff like that. Think the only really major thing I've left to do are the suspension bushings.

I've pretty much rebuilt or in some cases outright replaced all of my engine compartment harnesses over time.

So far as weatherstrip, anything other than Corvette Rubber Inc is, in my view, a waste of your time and money and you'll more than likely be doing it all over again.

Brakes are, in my experience, a repetitive process of flushing and bleeding several times until it's right. It's one of the things that you'll find have likely been the most previously neglected aside from coolant maintenance.

An OBD1 Tech 1 tool, if you can find one, is worth snatching up...

 

Is there much difference from Tech1 and Tech1a I have seen both reccomended. Yeah the brake fluid was BLACK I dont think it was ever serviced and the rotor is warped. Im hoping with the new loom and electrical tape I wont have to touch the engine harness for another 40 years lol. Just have to fix the connectors that broke in the process

 

A 1a has a couple of extra ports with added pc connectivity.

It's getting so that you jump on what comes along, though, with them.

There are places that carry a variety of our connectors. I have them bookmarked, I think. Will have to look and see...

 

Well heck. I don't have any of them bookmarked any more.

 

Aw shoot, appreciate it tho! Whats so special about Tech scanner versus the other ones you can get?

 

The main thing (that I know of anyway) is that with the Tech 1 you can work the ABS to thoroughly flush and bleed the brakes. Which I do not think that others can do.

No idea what other differences there may be because I never looked for anything other than a Tech 1. Mainly because that's what the GM techs were using way back when these were still being produced in order to diagnose and make repairs.

I landed one for myself for Christmas but have only started reading through the manual and haven't used it yet. Likely won't until Spring rolls around. My C4 is hibernating for the long, cold winter. Doesn't even have a battery in it. Once the salt hits the roads, that's pretty much it for the season around here.

Just as an aside, and while I'm reminded of the ABS system, maybe tuck this little gem of a thread away some place for reference later. Thanks to user @Tof for taking the time to share what he learned about servicing that thing.

https://www.corvetteforum.com/forums...issaembly.html

 

I will definetly keep that bookamrked I appreciate that. I really am hoping its not the ABS from what I have seen those can be pretty expensive. The weird thing with the wheel is that it can spin freely now it use to not be able to do that before caliper replacement. But the brake line did not freely bleed. When I go back down to work on it we will most likely try to bleed it out all corners this time. (Correct me if im wrong but it should be furthers brake to closest brake with reference to master cylinder so PB, DB, PF, DF)

 

On the '90 its front right, rear right, rear left, front left. That's what is described in the factory service manual for the car.

And yes, this actually is farthest to closest on the 90.

Some contend that it doesn't matter and I suppose that depends on what bleeding/flushing method one chooses to use.

I like the two-man method myself (repeated several times). It's the only way I've ever got a good pedal on this car.

 

When it comes to caliipers I'd prefer to rebuild over replacing any day. Especially if yours are original and you care about that kind of stuff. You can rebuild all 4 for less than a single aftermarket caliper. And it's easy to do.

If they're original, they're due to be rebuilt anyway. Also a good time to clean em up. A lot of people paint em, but I like the raw aluminum when it's cleaned up.

 

We tried to sand them down as a sudo rebuild but the cylinder walls were way too pitted so it did not make much of a difference. It had a lott of gunk in it so I doubt in 40 years its been serviced once. Luckily the back calipers seem fine so I plan on rebuilding those.

 

Yeah, the front breaks get most of the action on these by design. It's actually kind of complicated how the brake balance works. To me anyway. I still need to do some reading up on that. Something to do with the bias spring in the master. I think. Ha...