67 caddy loosing coolant

[BK911]

Preparing to pull the pimp mobile out of hibernation and noticed she was almost out of coolant.
I have had to top her up after every couple of rides, but not that much. Maybe a quart every 100 miles or so.
Figured head gasket but no white smoke from exhaust.
But now I had to add about a gallon and that was with zero miles driven but a few months of being parked.
She started right up with a little magic fluid and still no smoke.
No noticeable water on floor.
Any ideas on how to trouble shoot?

1967 Cadillac Convertible

[Nostril Cheese]

Id check the oil first, see if there is any coolant mixing. After that, a compression test to see if all is good.

[tevake]

Any signs of leaks while parked? It would be nice if its a leaking hose or other externals.

Cheers Richard

[varmint]

Start fresh. I don’t remember a coolant flush as being that big a headache.

[Zeke]

Water pump bearing and seal are the usual go to look sees. Sometimes the water leaks but evaporates before making much of a puddle. When running it can easily evaporate off the block but should leave trails.

How's the cap? Are you using a pressure cap? The correct one? They aren't one-size-fits-all.

[1990C4S]

Do you have a coolant pressurizing pump? I'd start there.

[wdfifteen]

Originally Posted by BK911

But now I had to add about a gallon and that was with zero miles driven but a few months of being parked.

It's on the floor or in the oil. But, was it really topped off when you parked it?

[BK911]

Oil looks good and is a little low.
Nothing on the ground.
It may not have been topped off when parked, but it definitely wasn't a gallon low!
I checked before every ride cause I knew I was loosing coolant.
Even carry a jug with me.
I tried a pressure test and I cant remember the specifics, but I do remember it didn't help.
Somebody recommended a compression test.
I prefer leakdowns, but would compression be better?

[BK911]

Original caps been replaced with a newer cap to allow a reservoir.
This change was made as one of the possible solutions of loosing coolant.
Odd thing here is loss of coolant without driving.
???

[BK911]

Just read about a UV dye kit.
Think that's my next step.

Still thinking head gasket, but no smoke from exhaust and lost lots of coolant without engine running. And no hydro lock when starting after loosing so much coolant.

UV dye then go from there.

Car runs good so still plan on pimping all summer!!

[Nostril Cheese]

Originally Posted by BK911

Somebody recommended a compression test.
I prefer leakdowns, but would compression be better?

Compression test would just give you a quick diagnosis if a head gasket is blown. Like $15 for a tester at HF. Leakdown testers are a bit more. Makes me wonder if the heater core may not have been filled up all the way to begin with. I have to imagine the core being bigger on a Caddy than the regular offering.

[BK911]

Will google heater core.

I have leakdown and compression testers.
No problem doing both, or either one.
Which is preferred for my issue?

[Bob Kontak]

Originally Posted by BK911

No noticeable water on floor.

As wd says, it's in the oil or on the floor.

If you are running water until you get the problem nailed then you know what I'm thinking. Seeping and evaporating.

I bought one of those ultraviolet kits from the Freight. Found a few problems with it.

I would do that and my money is on the water pump area given your oil is looking fine.

[Nostril Cheese]

Originally Posted by BK911

Will google heater core.

I have leakdown and compression testers.
No problem doing both, or either one.
Which is preferred for my issue?

leakdown will be more precise, but take more time.

[Nostril Cheese]

FYI...

a tool like this makes it a really simple job. I have the Airlift one, but there are others. Draws a vacuum on the system, which presents leaks in the system and also allows a complete fill with coolant..

[wdfifteen]

Originally Posted by BK911

Will google heater core.

I have leakdown and compression testers.
No problem doing both, or either one.
Which is preferred for my issue?

Pump air into each cylinder with the leak down hose. You should be able to hear where the air is going. Bubbles in the radiator - head gasket. Before I loaned it out I had a cooling system pressure tester. You could pump it up to a few psi and watch for the leak. Or start the engine and pump it up and listen for a misfire.

[1990C4S]

Originally Posted by wdfifteen

I had a cooling system pressure tester. You could pump it up to a few psi and watch for the leak. Or start the engine and pump it up and listen for a misfire.

This is the direction I would go. Pump it up, listen for a leak, or let it sit to see of it can hold pressure.

[Superman]

I question whether water would move past a head gasket while the car is only sitting. No water in the oil means it's not going there. If there is no puddle on the floor, then it's either leaking slowly enough to evaporate or it's inside the car - heater core.

The first thing I think about when a car is losing coolant is water pump. They wear out. The impeller shaft just sits in a bushing, which wears. Conventional wisdom is that the water pump is one of the parts which should not be replaced with a rebuilt or remanufactured one. Brand new is the recommendation. Take your time and don't scratch the gasket surface.

[Por_sha911]

Turn on the defroster with the heat on. Leaking heater core sometimes shows up with fogged windshield and has that sweet coolant smell.
Pull the plugs and see if there is signs of coolant.
Pressurize the radiator cap and look for milk shake in the oil.

[Nostril Cheese]

Any updates?