hdal

78' 34,000 mi with A/C. Everything in dang car works as should and now with heater on I noticed a wet area under the floor mat. Looks to be coolant on Oyster carpet. Lord please don't tell me the heater-core is leaking! Looks to be quite a chore getting it out. Anybody got any secrets or test? Hdal

danh77

When I changed mine I searched on here and read many posts first. It might have been overkill but I changed both hoses and also all the seals on the case at the same time. Mine is a 77 and I know your dash is different but I did have to remove the rt side dash. Get a good replacement core, I bought mine from Wilcox, as I didn't want to put in a junkie parts store one. It's not to bad a job, it just takes time.

Easy Mike

Does it smell like antifreeze? You almost certainly have a heater core to replace.

hdal

Thanx danh77 for the inspiration and tip on Wilcox. If it's recore-able I have a good radiator guy up the road. As for what color/smell,hard to tell. I sopped-up most moister with a wh towel and didn't show tell-tail. One things for sure,the car hasn't seen rain or a wash in two yrs. The rubber back side of flr mat is still wet after overnite and in the sun this morng,leads me to thing,yeah coolant. Hdal

KapsSA

You'll probably remove the seat to work on the heater core replacement.
REMOVE the pass side carpet too and thoroughly flush the coolant soaked area with plenty of water. Hang it up to dry. You'll be glad you did.
One of mine came to me with a replaced heater core but the carpet was always grimy feeling. I had occasion to remove the carpet and flushed it out like I recommended. Had to use vinyl paint on the area because it looked like it was bleached out.

hdal

Hey Mike,good tip on rinsing the carpet,I was wondering about that. So far it looks to be a sm leak as I could barely get any moister otta a quick shampoo and wh rag. The pass seat will definitely come out as they are new this yr. Will the A/C hsg in the eng bay have to be removed? Curiously,I've been noticing the ctr dash gauges fogging up when the car was covered.Lifted the rt si mat and bingo,I think I know what's going now.

danh77

If your 78 is the same as my 77 then no you won't have to remove that half of the heater/ac box.

DUB

I have many tricks and I have replaced many heater cores. Keep in mind I do this for a living so I am not trying to save the customer money. I know that statement may seem harsh....but here is why.

My time is worth money. So if I spend an hour trying to save the heater core and hoses so it can be re-cored...because I have to fight with the hose clamps that are hard to get to due to how it was assembled on the factory line. IF the time I spend is more than the cost of a new heater core...I cut the hoses and tubes and get on with it.

YES...you do not remove the 'dog house' on the firewall. And when I replace the hoses that go to the heater core..I get the ones with molded 90 degree ends on them and NOT use bulk hose off a spool.

DUB

Rescue Rogers

Have you determined its antifreeze yet? Just asking because if the humidity has increased in your area, and youve been using the A/C, it could be the box drain is plugged and its just water spilling out. Otherwise good luck with the core replacement!

hdal

Ow,Rescue,you could be onto something! Where is the box dr plug? I did use the a/c fairly often.This last ride was 1st time I had the heat/sw on. So could it have been the fact the coolant hasn't traveled thru the core all summer? Visually,I can't see or feel the leak.Hdal

danh77

I'm only going off memory here but only drain I recall is outside, can't imagine GM putting a drain that would go in car, my guess would be that is why the evap core mounts outside the cabin. I was lucky on mine in that I could see coolant leaking on the bend of the heater hoses Dub spoke of. Finding leaks be they coolant or water is more often than not difficult because where you see the drip isn't where the leak is, it is just the easiest exit it travelled to. For your sake I hope it is a simple issue but from my personal experience you have listed every thing pointing to a core.

DUB

'danh77' is correct. The only drain is for the evaporator core ...which is on the firewall side. SO...condensation from the evaporator core can not get to the inside of the cabin. that is just not going to happen. And that is assuming all is correct in regards to the evaporator core side of the A/C box. The amount of moisture/liquid that would have to collect and 'possibly' back flow into the heater core are would be quite excessive.

There is NO drain for the heater box. What will happen is that is can fill up with enough coolant and sweep out into the cabin by where the heater box mounts to the firewall.

DUB

news2me

The heater core on my 77' with A/C went a few months ago. I put a bypass in to get me through the car season. After Thanksgiving I plan on sending it into the shop and get it done. The guy that does my work, wants to re-core my old one. He doesn't like the new aftermarket ones, he said there all made like ****. The tubes don't line up with the fire wall and you have bend them to get them to fit. And the new one ends up leaking.

hdal

Dub,good information! I now have a better understanding of the core/box and drain location. Hdal

hdal

News2me,keep me in loop as to the re-core. I'm also considering having a shop fix the leak. If you will let me know how much it cost.Thanx,Al

news2me

I think I'll send it in the first of December.

DUB

It takes about 4 hours if all goes well and no other items are being repaired at the time the heater box is out of the car.

Look at post #15.

https://www.corvetteforum.com/forums...ater-core.html

DUB

Rescue Rogers

the drain on most cars does go to the outside, when it plugs it back flows into theheater plenum and sloshes around until it comes out the heat vents, you can stick a swap or rolled up paper towel into the heater floor vents and see if theres any fluid back up in there. I agree its a shot in the dark but pulling the heater when you dont need to is a pain. Once you get the core exposed, you could get a radiator pressure tester before you pull it and see if any fluid bubbles out any where. Has the fluid level in your over flow tank dropped?

news2me

That's what I was thinking 4-5 hours, if you know what your doing. Plus the Core, Heater Hose's, Anti-freeze and a few Clamps. And anything else they find they needs replaced. I read on another post something about a water valve...

OldCarBum

Pressurize the system by using a tester or just start the motor and let it warm up. With the motor running, lay on the passenger side floor and feel around up under the dash and find the drip. A pinpoint leak may not show up with the motor running and the system will increase pressure after you turn off the motor. Check it again a couple minutes after you turn off the motor. Condensation won't have a slimy feel and won't smell like anti freeze. Open up your AIM and look at how the core is installed and what it will take to remove and replace it. It isn't difficult, just takes time and patience.