1993C4LT1

210-220 is normal for these cars. Cleaning that road debris will help.

A26B

Not strange at all. You still had air trapped in the engine coolant system. The overflow tank performs in the manner you described. The air bubble finally purged itself. As the engine cooled, coolant was drawn from the overflow/surge tank, into the engine.

Air trapped in the engine cooling passages has always been an issue, and there are a variety of methods to mitigate the problem. For me, I just fill it back up, top off the overflow tank, take it for a short drive to warm it up, then park it for a cool down. Open the top tank, fill as needed +fill the overflow tank to proper level. Take it for a drive, keep an eye on the temps, hit 7K a couple of times & park it again for cool down. At that point, all it's ever taken was a little more in the overflow tank.

There's no substitute for removing the radiator to clean it effectively. Sort of like the leaking oil pan gasket..... you might relieve the symptoms for awhile by tightening the bolts, but it's not a permanent cure for the ailment. Same is true for cleaning the radiator, gotta pull it to fix it.

You're doing a great job, systematically going through everything & doing the job thoroughly.

Gonzo_65_L76

Yeah... in my entrepreneurial life I've gotten quite accustomed to there being no shortcuts to doing things right.

Kinda interesting - it's always been on my bucket-list to take possession of a true barn find. Being about ~75% through this adventure (that's probably optimistic), I can honestly say I'm glad to have done this. But, to do it again, it will need to be a very special car. VERY special car. This is a lot of work, and more than typical rebuild / refurbish.

-Gonzo

bowtiguy

I was JUST having this conversation with a fellow car buddy at a cars & coffee last month. I drove in my parents 84' medium blue metallic/blue 29K survivor after putting over 40 hrs of work and close to $2K of parts into it. I sold it THAT DAY but we both are a bit older/wiser to "pick our fights". I prefer the "minor restoration cars VS. full build any more. BTW, I LOVE following your thread. I just picked up a 9,700 mile deep red metallic ZR-1 yesterday. It needs a bit of TLC but NOTHING compared to what you've done so far. Drives like a dream ( sorry, didn't mean to rub it in) but I'm still pulling the plenum to get that area cleaned out & get new gaskets injectors in there ( even though mine are working fine). keep up the good fight!

Gonzo_65_L76

Yeah. Luckily, I got a good deal on the car, but depending on how you price my time... I'm gonna still come in a little under what the car will be worth with all the kinks worked out, and 60k miles. To date, I've spent about $2k in parts, fluids, misc cleaners, rubber gloves, solvents, etc... I need new tires (~$1200), and probably need new exhaust (cracked welds at muffler) for another ~$1200. Throw in problems yet to be discovered and I'll be at least $5k.

-Gonzo

Z51JEFF

zrc3john

Years ago in NY, back in the "day" as you would call it, you would give your mechanic 75 bucks and miraculously you would get an inspection sticker next day....Some shops still would do that...I'm guessing more than some, with the set ups I see some guys run in NY....

Gonzo_65_L76

Not in CA. The smog test machines are connected directly to the State. To run a smog test, you need to enter the VIN of the car. The automated test connects directly to the DMV to prevent shops from doing what apparently is doable in NY.

I thought I read that the Stainless Works LT headers (with cats) would pass a smog test. Can't remember where I saw that. I still need to get my initial smog test before I go too far. I'm planning to have a heart to heart with my local shop where I plan to do the smog. My guess is they will have a few pointers for me.

-Gonzo

Gonzo_65_L76

I didn't get to touch the car this last weekend. Too many kid events. So... I opted to take her out for a ~85 mile drive through the Santa Cruz Mountains, down to the coast, and then back through the hills to home. The goal was to put on a nice even 100 miles since getting everything back together so I could do a quick oil and filter change to purge as much of the old oil as I could from what I couldn't get to in the oil cooler, and check to make sure there were no serious issues.

Immediately getting out on the highway, the car felt great. Temps were right about 180... tons of power... the engine SOUNDED awesome. Life was good. Then I got off the highway for a quick low-speed detour, and temps started rising. I figured out the little dance to show the digital temps. I was guessing the analog gauge was showing ~20 degrees high. Turns out it's only about 10-sh, or about 5% at anywhere on the gauge (once you do the conversion from C to F). What this did prove is that the car is running hot everywhere but on the highway.

Then came the Santa Cruz Mountains. 'Mountain' is a strong term here. Max elevation was about 2500 feet... but still some decent up. Immediately, the car jumped to about 250 indicated (see pic below) or about ~240 true. I decided to ride it out as the temp wasn't going any higher, and the summit was very close. At the Summit, I spent some time just cruising the top of Silicon Valley on Summit Rd. Nice spirited driving at about seven-tenths to play with the LT5. Throughout this, the temps stayed around 220 until I decided it was time to descend down to the coast. Of course, the temps returned to ~180 on the descent. After driving along the beach for a while, I decided to climb back over the hills. Once again, the temp started to rise to around 240 (250 indicated). Clearly something is wrong.



Once back in the garage, I started looking at how difficult it would be to pull the radiator. That's when I noticed there is a gap on the passenger side of the car where you can look down between the rad and the condensor and oil cooler. That's when I had to do a double take. Wedged ahead of the radiator... a dead rat. In fact, I think there's at least two in there! I'm still in a state of disbelief... but a picture is truly worth a 1000 words... take a gander at the below.



I'll be reading all the posts I can tonight on pulling the rad. Hopefully I can get to that tomorrow

Also of interest today... the car is getting a combined MPG of 12.5mpg. Based on a few forum posts I've read, replacing the O2 sensors seems like a very good idea (that's likely the last emissions related part I have not yet replaced). My first order this week to Jerry went in around 2pm PST... not sure if that gave Jerry enough time to get those in the mail today. Hopefully they will be here by Friday.

And then more 4-letter words...

While doing the oil change with the car on the lift, I noticed there was fresh oil on the front of the oil pan!!! It was less than what appeared to be leaking before... but enough to be a problem. I removed the K-member with the intent of checking the pan bolts, but noticed that there was oil as far in front of the pan as I could see with a light. That seemed to infer this was NOT coming from the pan. On a whim, I dropped the small cooler (power steering fluid?) just below and in front of the crank pulley, and saw that the area behind the crank pulley was caked in oil. I then grabbed my torque wrench and checked the torque for the bolts holding the engine cover behind the crank pulley... ~9 ft-lbs. Should be 19 ft-lbs. Hmmm. I don't see any way of getting that cover off and putting a new gasket in there without pulling the engine. So, I pulled the 5 bolts on the bottom half of the cover, ran them through my M8 dye, coated them in loctite, and torqued them back in. I put my chances of fixing this at about 30%. At the very least, it should slow the leak down some. Anyone have any bright ideas with this one?

The oil change was joyfully uneventful. As I expected... I flushed about $100 worth of Amsoil and filter that I probably didn't need to, other than for piece of mind. I'll cut the filter tomorrow to be sure, but the oil came out about as clean and transparent as it went in. Once I cut the filter open and inspect... I will feel a whole lot better about driving harder.

Another question for the pros - Since I need to pull the rad out of the car... it feels prudent to replace the radiator as I'm 99% certain this is the original radiator. Ordering it today (with 2nd day shipping) would mean I could have it all put back together before the weekend. Looks like Dewitts has a nice AL jobber that drops right in as a bolt-on replacement. I put a Dewitts in my hot-rod'd, 500hp '65 Stingray and could not be happier. I'd love any advice folks have to share.

FWIW, other than the issue of running hot... The car is starting to feel sorted. Steering is tight. Suspension is solid. Engine just wants to rev and rev... and then rev some more. The interior is clean. Life is mostly good. The clutch feels a little worn - Doesn't fully engage until the top of the pedal, and I can feel a small slip at redline shifts between first and second. I can also hear a small exhaust leak. This is probably due to the car missing at least 3 manifold bolt. Gonna try to get those replaced ASAP... This could be causing the O2 sensors to read incorrectly as well.

After today, I feel like I've rounded second, and am coming up on third. I'm not quite headed for home plate yet, but getting there.

-Gonzo

mhobtr

It is normal for there to be missing bolts in the exhaust manifolds See http://www.jerrysgaskets.com/bolt-ex...old-90-95-1d2/

If you have not done so already, you need to flush your clutch and brake hydraulic systems with new fluid. Then you can evaluate your clutch operation if it is still spongy.

I bet that stock radiator will be fine after you give the rats a decent burial and clean it.

Bad or faulty O2 sensors will throw a code. You need to find a Tech 1 or Tech 1A diagnostic unit.

Gonzo_65_L76

Hmm. I've spent the last 90 minutes searching ebay, craigslist, and google. I cannot find a tech 1 or 1a scanner for sale. Anyone have any idea where I can get one of these?

I read about how to short the pins in order to pull the codes... but would love to have a scanner instead. It looks like this scanner would work... can someone confirm?

Mike.

zrc3john

Your 100 mile trip through the mountains sounds like a lot of fun.. Gets me thinking, how could the previous owner with all those spirited roads just let this car sit ? Its one thing if you live in a very urban area such as I do, but to live in an area where there seems to be practically road courses in your backyard, how could you not keep this car through its paces?

Gonzo_65_L76

Just got off the phone with Dewitts. They are currently out of stock on the double row rads for ZR1s. They'll have a new run in 7 days. Add in shipping... and I should be able to solve my heating issues in about 2 weeks. I guess no hill climbs until then.

I did think about pulling and cleaning the old rad. It just seemed like a halfway solution considering that I want to spend a fair amount of my free-time at Laguna Seca once I get everything dialed in. A double row AL radiator seemed like the prudent approach; especially considering the excellent performance I've enjoyed with the AL Dewitts rad in my '65. Apparently there are a few extra plates and brackets for the double row radiator to fit properly in the ZR1. I don't anticipate any issues.

-Gonzo

1993C4LT1

Can't go wrong with DeWitts. Good choice

Gonzo_65_L76

Whoa. In preparation for my scheduled smog test next week, I've been reading all the info on CA smog testing the ZR1. That is not happy reading...

There's nothing I've found that's conclusive, but it appears I need to undo my mod that permanently wires the secondaries open. Is there anyone out there who's passed a smog test with the secondaries permanently on? It actually seems odd to me that the car would pass with them closed, but not open. I would assume the mixture is the same, and that the same volume of air-fuel is required to spin the motor with enough power to move the wheels 15mph and 25mph with or without secondaries.

One thing I'd like to understand is what happens when you turn on 'full-power' mode with the valet key. Does this do anything other than open the secondaries with vacuum and turn on an LED?

I'd value any advice on this. I'd rather not pull the plenum again, but will if I need to. I've already designed up a non-vacuum switch to open and close the secondaries if I need to pull the plenum. My appt is on Monday.

-Gonzo

1993C4LT1

OP, I hate to be annoying. Honestly. But have these guys not told you that the analog coolant reading is inaccurate? When new, these cars had stickers on the instrument cluster saying that the analog is not true to actual temp. You know the button that says "gauges"? Press it, until you see "cool" and bam, you have an accurate reading. I am saying this because I just saw your pic of the analog temp gauge. Also, many new C4 owners think there cars are over heating. So I always do my best to tell them about the digital reading. Crazy about the dead rats!! Still, going Dewitts is a wise choice.

Gonzo_65_L76

I accessed the digital temps through manipulating the fan buttons on the center console. Digital temp was only ~5% lower than analog displayed temps.

Thanks.

1993C4LT1

Yeah, that doesn't sound correct.

DRM500RUBYZR-1

That is great that you have a picture that depicts what is often the situation.
More than half of the cars that come to me for "overheating" are not overheating at all.
I explain it a million times, but your picture certainly drives the point home with a sledge hammer!
Thanks for posting it!
We should always use it as step one in helping people determine if in fact they have an issue, as usually there is not!
Marty

Gonzo_65_L76

Interesting. I will try this out.

There is another method for displaying the temps in the center console -

• Hold down fan up and down buttons until you see "00" in center console
• Fan up button a bunch of times until you see the value "16" displayed
• Hit the fan auto button

I assume your method yields the same value... but through an easier set of steps. Also, the value in the center console is displayed in degrees celsius.

-Gonzo