Cabin Heat Problems

I took a longer drive with the Corvette and noticed that adding Stinger Roadkill to the cabin did not solve the heat issues in the car. It just took a bit longer for the cabin to become a sauna. So more needed to be done. I spent some time googling and many others have the same issues with C3 Corvettes. I found three different issues that I addressed:

1. Heater core isolation
2. Hood weatherstrip
3. AC and heater box sealing

Heater Core Isolation

The biggest issue was the heater core. I found that the heater feed hose should have a vacuum operated valve that cuts the water circulation when the AC temperature setting is in cold. The valve was missing so it meant that the heater was always working at full power! No wonder the cabin temperature rose...

Seems that many people have problems with the vacuum valve and have replaced it with a manual valve. As I only drive during summer, the heater is not really needed so I decided to do the same. And I can get a manual valve from the local hardware store as opposed to ordering from US. To completely isolate the heater core, I added valves to both hoses. Otherwise heat can creep up through the drain hose on long drives.

I found some nice, small ball valves, cut the hoses and installed them. It will be easy to replace them later if I decide to install an original vacuum valve. When doing this, just note that the feed hose (from the intake manifold) needs 1/2 inch nipples and the drain hose 3/4 inch.

While doing this investigation, I also realised that I need to find the vacuum hose that should feed the valve. And I found it sticking out from the firewall under other hoses and wires. It had been cut so it was causing a vacuum leak! No wonder the other vacuum operated valves in the dash did not work correctly.

Hood Weatherstrip

Another common reason for cabin heat is a perished hood weatherstrip. Mine was missing completely. I've had one for years but had not installed it yet... This allows engine heat to enter the cowl area where the fresh air intake is. This could be fixed with a little drop of glue so I got that sorted in a few minutes.

AC And Heater Box Sealing

While working under the hood, I noticed that a lot of air was flowing out of the heater/AC box. Sealing was mostly gone so nearly all of the fresh air from the blower escaped through the seams to the engine bay. I did not have the sealing kit available so I stuffed some foam in the gaps.

Results

I've taken some shorter drives with the car after these changes. Cabin temperature has dropped to much more tolerable level. It's still pretty warm but nowhere near the oven heat it was before. I also noticed that the car is much quieter now with the hood weatherstrip in place. I guess a lot of air was flowing through the gap as it was causing wind noise.

Unfortunately sealing the heater box did not fix the poor air flow in the car. Even with the blower at full power, there's hardly any air coming out of the vents. I'll need to investigate that a bit more.

Parts Received From Big City Corvettes

Santa arrived late and brought me a note in the mail which said that the order from Big City Corvettes had arrived to customs. I jumped straight to my car and drove to the airport to get it. I had to pay over 130 euros of tax and then the box was mine.

Back at home I inspected the parts and everything seemed to be in order. The box was well packed and all used pieces were in good condition. Now I'll just have to find some time to install them. Unfortunately it has been really cold around here for the past weeks so spending time in the garage is not a pleasurable experience.

Ordering Interior Parts

I've been missing a few interior parts from my Corvette. The rear window frame and lower trim, center console side panels and horn button were the most visible items. In addition both side AC air ducts and driver side vent were missing. As the car was otherwise complete, it was time to start hunting for them. You can get reproduction versions of the interior panels but not of the ducts. So I went to eBay to get original parts.

I tried emailing some used parts sellers but never got a reply. Until I found Big City Corvettes that is. They replied quickly and had the AC parts I was looking for. Unfortunately they didn't have the interior panels in the colour I needed (Firethorn), but promised to order repro versions of them. The horn button was not available, but I really want to replace the steering wheel anyway so it was left out. I waited a couple of weeks and just received a confirmation that my order has been shipped to Finland! Now I just have to wait until the parts get here and go through customs. Oh, and pay the 24% VAT and 4,5% customs tax.

As a bonus I also ordered yellow side marker lights for my car. The red marker lights are illegal in Finland so I'll replace the rear lights with yellow ones. I've read that they should fit right in.

Insulating the Corvette

While driving around with the Corvette last summer, I noticed that it got really hot after about 100 km. Especially around the legs. Well, there was hardly any insulation in the car and the engine and transmission did produce a lot of heat so perhaps I should have guessed it. The car was also pretty noisy but that was secondary compared to the temperatures in the cabin. This time I decided to do the insulation right by getting some good stuff.

My friend had used the Stinger Roadkill in his -65 Mustang and said that it was easy to install and worked well. I also went for a small test drive with him and was pretty amazed how quiet his Mustang was. Almost like a modern car. So, I bought three trunk kits that each had 1.85 square meters (20 sq. ft.) of material. Over 5.5 square meters in total. I read from some discussions that 5 to 6 square meters should be enough to cover the whole interior.

My plan was to remove the carpets and some interior pieces so I could insulate as much of the car as possible. Again the small garage worked against me so I had to work one side at a time. This time the weather was also an obstacle. When I started the work, it was about 5 to 10 degrees outside and going down. I would have to work fast before it got below freezing. As the Stinger was mostly meant for sound dampening, I planned to install two layers to the hottest areas: firewall and transmission tunnel.

I started from the driver side. I removed the seat, kick panel, carpet and the old "insulation". It was so crappy that most likely it didn't do anything... The floor that my friend built three years ago still seemed to be in good shape thanks to the rust proofing we sprayed.

Old "insulation"

Floors still good. Maybe a bit dirty.

The Stinger boxes said that no surface preparation would be needed but I still made sure to remove all dirt with some acetone. After wiping the floors, it was time to start installing. The Stinger comes in 30 cm by 61 cm sheets and should be cut to correct shape with a carpet knife but it is so soft that I even used scissors in some places. Starting from the largest level areas, I worked towards the walls and corners. After removing the backing paper and carefully placing the sheet, I used a roller to firmly attach it.

Attaching one of the first sheets

It took me a few hours but finally the floor was done. I also added some Stinger to the lower halves of the doors. The higher parts of the doors have some crash barriers so I couldn't get any insulation there.

Driver floor done.

Insulation in the door.

Next I turned the car around and removed the passenger side interior. The floors seemed good there too so I just cleaned them and started rolling.

Passenger floor.

When both floors were done, it was time to check the trunk. I still had a full box of Stinger left so I removed the carpets and old insulation and got to work. Unfortunately after a while if got too cold to work any more. I got everything else done except the wheel arches until the temperatures dropped below freezing. Then the Stinger just would not stick any more and fell off the walls. Luckily the glue hardens after install so the pieces that were done earlier are fine.

Hopefully the many layers of Stinger in the firewall make the Corvette a cooler place next summer. Unfortunately I won't feel or hear the difference until spring...

Fixing Power Windows

I've had a small problem with my power windows: the motor could not lift the window all the way up. I had to help the motor a bit with my hand. While reading the Finnshark forum, I found an explanation that this is caused by the spring in the window mechanism. It needs to be preloaded by half circle to be powerful enough for the window. The annoying bit is that to do this, you need to pretty much disassemble the whole window mechanism...

Well, all I had was time so off to work. I began from the passenger side as it was still missing the window motor. I ordered one almost eight months ago but still had not received it. First I loosened the two nuts that held the window in place and lifted it out. Getting everything else out was simple job of unscrewing a few bolts.

Preloading the spring was also pretty easy. I turned the window regulator over until I could just put the spring in place. Then loaded it by using the arm as leverage. Putting the mechanism back in the door was a bit trickier now that the spring was loaded. I handled that by putting a zip tie around the arms. Now I could put the glass back in and finally tune all the settings so it moved correctly.

The driver side was the same deal. Only this time I also put the motor in. I tested it and now the window rose all the way up without problems. So the passenger side should also work when I get the new motor.

Passenger Side Emergency Brake

I was messing around the garage tonight and decided to check the passenger side emergency brake. I jacked the Corvette and removed the caliper as before.

Everything went smoothly and I started checking the system. This time the brake mechanism itself was OK but the shoes were not that good. Most likely they had been dragging for some time and overheated. This had opened some cracks in the lining. They were still in one piece though so I decided to put everything back together and hope they would last my light use.

Finally I adjusted the shoes and put the wheel back. I didn't take the car for a test drive but the emergency brake handle was quite firm now so hopefully this problem is finally solved.

Emergency Brake Problems

Like mentioned in the previous post, my emergency brake was not working properly. Because of this the car failed its inspection and could not be driven any more. Luckily the driving season was pretty much over already so I decided to leave the fix for later. This was a month ago so I thought that now would be a good time.

As tuning just the cable or adjusting the shoes through the hole in the brake disk didn't work, I needed to see the mechanism itself. This required me to remove the brake caliper and disk. The driver side was worse according to the inspectors, so I began there.

I removed the two bolts that held the caliper in place and then hung it from the frame with zip ties. Now the disk could be just pulled off. Pretty soon I found the problem. I saw that the actuating lever had slipped off the other shoe and actually didn't spread them at all. A few minutes with a screwdriver fixed it. I couldn't find anything else wrong so I put everything back together.

Naturally I needed to tune the brake shoes and the cable again but after those took a short test drive. The brake felt much better already but perhaps I'll check the passenger side too later...

Wheel Alignment, Carb Tuning And Transmission Fixing

It's been a while since I last fiddled with my Corvette so it was time to go back to business. I drove the car about 130km to Tampere to see my car mechanic friend. We had a few tasks on our list: check the wheel alignment, see if the carburetor was tuned correctly after my rebuild and open the transmission to check the shifter linkage.

The drive to Tampere went fine except for the heat. The cabin of the car got pretty hot after a while and it was quite noisy. The Corvette also didn't seem to like the highway. If driving over 100km/h (62mph), the temperature of the engine rose. Not enough to overheat but enough to limit the speed to about 90km/h (55mph)...

Carburetor tuning

We began from the carb as the car was hot after drivin it to the garage. I had rebuild my Holley 80457-S during winter so I had no idea if it was tuned correctly. We placed the probe in both exhaust pipes individually and checked the readings. Idle HC was about 100ppm on both sides and CO about 1%. This meant the engine was running pretty lean!

We loosened the idle screws and got the HC values to about 300-350ppm and CO to about 5% - 5,5%. This was much better.

Next we tested the engine at 2200 RPM. CO dropped to 1% again. I guess this means the carb needs larger main jets. This could also be the reason why the engine gets hot on the freeway as a lean mixture burns hotter.

Left exhaust reading

Right exhaust reading

Wheel Alignment

Next on the list was the wheel alignment. I drove the car on a lift and my friend set up the gear. I didn't know how to use the equipment so I just stood out of the way and looked. It took some time but finally we had the results: both front and rear alignments were within specifications! This was surprising as a lot had been done to the suspension since the last alignment: front springs had been cut, rear had been risen a bit, rear bearings had been changed etc. Oh well, I'm not complaining as this was a much easier job than expected.

Transmission Surgery

I already opened my TH-350 transmission once during winter to tighten the shifter shaft nut. This cured the missing first gear for a while until the nut loosened again. So I knew the transmission was working but the shifter was not.

We drained the oil and dropped the pan. After some examination, my friend had a revelation. Here's the old photo from winter.

It's a bit hard to see but there is a washer on the shaft. But not between the nut and the plate but between the plate and the clip that holds the shaft in place! We removed the clip, opened the nut and pulled the shaft out. Quickly we saw that with the washer in place, the plate never locked to the shaft but just rotated around. We switched the washer to the other side of the plate and put the transmission back together. Wow, even after working with the car for this long, we still find surprises like this...

Finally we decided to switch the speedo driving gear too. The only one I had found before had 10 teeth but after driving a while, I learned I would need a 8 teeth one. The speedometer was showing way too high. Changing the driven gear would not help as I would need a 24 teeth one, but the largest one for TH-350 had 22.

So we pulled the end of the transmission and removed the old, blue gear. I got the correct black one from US-Parts again but something was wrong! The gear was really loose on the transmission shaft. The old one was really tight but this new one was about 1 millimeter larger in diameter. This also meant that the clip that should hold it in place didn't work.

We had to cut the gear up a bit and push a split pin under it to hold it in place. We could only hope it would work and put the transmission back together. Unfortunately it didn't work as the speedometer didn't work at all after this... *uck!

On the return trip the engine still got hot on the freeway and cooled after a few kilometers of slower driving. I need to adress that issue later and go back to the speedo gear too...

Loose TH350 Shifter Shaft

UPDATE 10.01.2013: Seems that the loose bolt was not the only problem: Transmission fixing

There had been a problem in my transmission for a long time. I could not force it to first gear with the shifter. I tried adjusting the shifter cable many times but it just did not work. The shifter lever in the transmission felt somehow loose when turning it by hand and just didn't go to first gear. I searched the net for possible causes and found that a loose nut at the inner end of the shifter shaft could be the problem. Oh well, at least that's pretty simple to check and I needed to change the oil and filter anyway.

Unfortunately I had to work in my really small garage again. To get some room under the car, I bought a pair of ramps. With them, I had just enough space to remove the oil pan. So I drove the Corvette on the ramps, added some wedges behind the wheels and got to work.

I drained the old oil to a container and removed the oil pan. It was exiting to see what it would look inside the transmission. The last time that I opened it up with my friend, it had probably been standing for a while. We were a bit worried how much crap had been stuck in the fluid passages and if it had loosened up after the car had been driven for a few hundred kilometers. The oil didn't seem too bad but there was some crud in the pan. The magnet was clean so at least it was just dirt and not metal.

I cleaned the pan and removed the old gasget. Next it was time to crawl under the car again and check the filter. I removed it and couldn't see any dirt. Hopefully most of the crap was now out of the transmission.

Finally I got to the part that I wanted to see: the nut at the end of the shifter shaft.

I tested the nut with a wrench and it did feel a bit loose. There was not much room but I could turn the wrench enough to tighten it. I tested the shifter lever and the play was gone! Perhaps the transmission was now fixed!

It was time to put the transmission back together. I screwed in the new filter, used some silicone to keep the new pan gasget in place and finally bolted the pan to the car. Lastly I filled the transmission with new oil and took the car for a test drive.

And what a difference this small fix made! The shifter was no longer loose and the transmission was much quieter. Previously there had been a jerk and clank when changing gears between reverse and drive. Now the shifts were smooth and quiet. It was hard to even notice when the transmission went in gear.

I still could not get the first gear activated as I had forgot to adjust the cable. While doing that, I noticed a small mistake. When tightening the shaft nut, it had turned the lever a bit. This meant that the cable had to be adjusted to its maximum limit and even that was barely enough. I still could not always get the shifter to first gear. It worked about half of the time.

Oh well, I'll have to tighten the nut again during the next oil change. At least the transmission works much smoother now.