gsimon767

I thought I might seek some advice. Car is a 75 Conv. With air. There is no evidence of moisture on the passenger carpet but--- Two things make me think the core is leaking. One, I have to add water to the overflow tank occasionally to keep antifreeze at the cold mark. Two, I had occasion to drive the car with condensation on the inside of the windshield. The defroster did not remove the condensation. If anything it made it worse.

The leak must be small. I am wondering if I should use some radiator stop leak as a possible solution or bite the bullet and replace the core? I hesitate to use stop leak because I just replaced the radiator and it is fresh and new.

If I do replace the core does anyone have advice on the best source for a replacement core. I have read horror stories about poor fitting and poor quality replacement cores. Corvette Central seems to have a properly configured core? Given the difficulty of a core replacement I only want to do it if absolutely necessary and I only want to do it once.

Iceaxe

Whatever you do don't use radiator stop leak as it will cause you nothing but future problems and expense.

I would get my cooling system pressure tested to see exactly where it was leaking from. I just went through this with my Trans Am and thought it was a leaking heater core. Turns out it was a leaking freeze plug.

Alan 71

Hi g,
You've had a pretty fortunate 'early warning' sign!
I'd replace the core before it ruins your carpet which is costly and takes some effort to install well!
Good Luck.
Regards,
Alan

I believe member Paul74 documented the core replacement on his 74 convertible in a thread.
You might want to search for it!
Paul is still on the Forum so you might want to ask him some direct questions!

https://www.corvetteforum.com/forums...a-success.html

vbgod1

While it "sounds" like a heater core, I would verify it with a pressure test. Nothing like spending that time and money, only to find it didn't fix it, or something else was leaking too and you didn't catch it.
Mechanics like silver bullets, and 90% of the time they work, but... That other 10% they get costly.

CanadaGrant

"I had occasion to drive the car with condensation on the inside of the windshield. The defroster did not remove the condensation. If anything it made it worse."

I'm with Alan on this one. If you were losing coolant with no other indication, there would be other places to look but the above makes it pretty obvious to me. Coolant condensing on the windscreen (it doesn't evaporate) would send me straight to the heater core. If you try to wipe it off it will smear. If you run your finger across it and taste it, it will be sweet. I wouldn't even bother pressure testing it and taking a good chance on ruining the carpet. Once you get at the core, it will be wet or damp if leaking. I would not use any sort of leak stop especially since you say it's a new rad.

KapsSA

I had a heater core leak on my78 that didn't wet the carpet at all. Went UNDER the carpet.
I noticed coolant dripping from the drain hole(plug) under the seat.

news2me

Any of you guy know, how much it cost to replace a heater core... Parts and Labor

Alan 71

Hi n2m,
This is a good question for someone like DUB.
I'd think he likely has more than a few replacements under his belt and has a pretty good feel for the labor costs involved.
The cores from the usual larger vendors seem to be around $80. He might recommend another source he's had success with.
Regards,
Alan

Dirty Dalton

I just had to do that in my VW. Condensation on the windshield, loss of coolant, and odor... $1800 IIRC. And, for good measure, my windshield somehow, amazingly, with no known reason, got cracked between the time I dropped it off and when I picked it up.

Good luck!

DUB

What year....and....WITH A/C or no A/C.

There is a difference....because one hose generally goes to the hot water shut off valve...and the molded hose that attaches to a heater core for a A/C car so it is not stressing the tubes of the heater core...and the year model due to placement of the hot water shut off valve.

So unless I know what year...and if the car is SUPER NICE....where more care must be taken....I would say.

Roughly an easy 4 hours....and then the needed parts. This time can grow easily. It could double ( but I doubt it)....I never know until I get in there and see what happens when I start.

I have learned over the years to know where to cut stuff to speed up the process.

DUB

Paul L

DUB,

I believe Mitchell says 6.5 hrs. My GM dealer will not take on the job. So I do it at home in about 8 hours.



In case anyone has thoughts of re-using the heater hoses, think again.



Start anew.

corvetero

It took me also around 8 hours on a 74 with A\C. Very important to label all the vaccum hoses

news2me

Its a 77 with A/C

0Willcox Corvette

On the 75 a/c car above we charge 4.0 hours do to the job. You must remove the right dash pad, the center dash bezel and then the inner and outer boxes. On a non ac car you can do this job from the engine compartment and it's really easy. On a a/c car it's not a really bad job but if it's your first go around on it then I say double my 4 hours.

If you decide to try this your self I'd make sure you get hoses in advance because you'll probably need them.

Go buy some hose clamps that look like these, you can buy these at Harbor freight cheap.. http://www.harborfreight.com/4-piece...set-65116.html. Use them to clamp off the heater hoses at the core and you'll only lose a tiny bit of antifreeze doing the job.

You should upload this file on removing the dash pad and center cluster, it has a step by step procedure on how do get to the console, center bezel and dash pad out of the way.

1968-1977-corvette-dash-pad-remove-and-install-instructions

The heater box will have only one nut on the inside, the rest are in the engine compartment.

The other issue is do not buy a core that is aluminum, they don't fit properly unless you make modifications. On a non a/c car you can remove the core from the engine compartment side but if you try to install a aluminum core you'll have to cut the opening in the fire wall 1/8" all the way around to get the new core back in.


This one will fit perfectly.
https://willcoxcorvette.com/corvette...itioning-68-77

Willcox

DUB

As I wrote before and I AGREE with WIllcox...the Mitchelll estimating guide I use clearly shows 4.0 hours for an A/C equipped Corvette.

But...it can take a bit longer if previous if idiots got into the dash and messed stuff up that would need to be fixed when trying to re-assemble parts that are held together with bubble gum and shoe string.


4.0 hours as the book shows above.

But the time can increase as I stated....and usually it has nothing to do with the actual heater core replacement.....it has to do with other stuff that is messed up. Such as worn/missign seals for your air duct work...busted plastic tabs for your shifter plate mounting....bogus wirign for an aftermarket radio....etc.

DUB

Paul L

DUB,

Thanks for the info re Mitchell. I guess that job could be done in 4 hours. But not by my Chevrolet dealer or me.

BTW, I really like and appreciate your posts!

0Willcox Corvette

Paul.. the Mitchell guide was based on "the day". When mechanics did this job over and over in a prefect world..
This throws a twist in things when you are dealing with a car that has rusted or broken studs, a heat box that is cracked and any other thing that can delay the process. We bill time and materials in the shop which is the only fair way to do it.

I talked with Kevin today and he can actually do the AC job in 3.5 hours which beats the book time..... But in all fairness he's done this job probably 10 times this year and that's if he is in a perfect world which as all us installers know, rarely exist.

It also helps when you know what tools, what size and what other items you need in advance of starting the job. This along cuts time way down. Years ago we started doing spreadsheets on jobs and what they required... We can look at the job, pull the spreadsheet and know what we need in advance..

Ernie

Richard Daugird

One good thing about living down here on the Gulf Coast, don't need heater! I am running the A/C today, usually do all the way till Thanksgiving. Never have replaced a leaky core, just doubled the hoses back!

Dallasfool

just was letting mine run for about 20 minutes today, then notice anti freeze dripping on garage floor, from passenger side, closest to firewall, my inside carpet isn't wet? it is an 1980 with air, since April purchase, only had to add a little anti freeze to over flow tank, I did replace radiator cap in sept, any help would be appricated

C3w4sp

You could bypass the heater core buy disconnecting the the hoses and connecting them together. That way you can verify it is indeed leaking and if so, it will stop any additional coolant from getting in the cabin.

In the interim, you wouldn't have heat or defrost but I can't recall the last time I used either.

I replaced mine (75 w ac) it took some effort and patients. At the time (hadent discovered the forum yet) I swore gm started with the core and built the car around it. Just the stuff on this thread would have helped.