Intermittent coolant leak

I have an American 1981 Rabbit Pickup w/ a diesel engine.

I have a small coolant leak from a hose above the gas pedal, on the side of the center console that contains the heater controls, etc. I can see the hose clamp where the coolant appears to drip from, so the question isn't really about where it's coming from, but when and why.

The coolant leak doesn't happen consistently. It doesn't even happen when I drive the car. If I clean up the small puddle of coolant on the floor, and then drive around for two hours it won't happen. But then if park in the driveway and let it sit for a day or two, I'll often find a new small puddle of coolant on the floor mat. I want to understand why this is happening. It makes it very hard to fix because I can't ever really "catch it in the act" of leaking. And so when I fiddle with the hose clamp I can't tell if it's actually making a difference.

I know the cooling system heats up and becomes pressurized when the engine is running. I would expect a leak to get worse under these conditions. But it seems to be the opposite, as it never happens while I'm driving. There might be some connection to the settings for the heater, but I haven't done enough testing yet so this is just a guess. Also, in case it's helpful or relevant, when the truck is cold, if I unscrew the cap of the reservoir under the hood, the trapped air hisses out and the coolant bubbles UP to sit higher in the reservoir.

Any advice is much appreciated.
 

Holed Heater Core Hose,
Broken Heater core, only 3 parts are inside the cabin, that is two hoses, and the heater core.

You might try to tighten up the hose clamps first.

Briano1234 Any ideas why it would only happen when the vehicle is cold? Is that a clue?

Maybe the hoses warm up and make a better seal?

emersonthis said

Briano1234 Any ideas why it would only happen when the vehicle is cold? Is that a clue?

Maybe the hoses warm up and make a better seal?

That is most probably the cause.

I had a similar issue but it was on the hose on the thermostat housing. I cleaned everything, replaced the hose, replace the jubilee clip but it still did it! I was told that I wasn't getting a good seal on the join and as the engine cooled you get contraction and slight movement of parts and a small bit of water can seep past while this is happening. Mine would stop once the engine was cold and I got over it by using a 3rd of a can of radweld.

Saulty said

emersonthis said

Briano1234 Any ideas why it would only happen when the vehicle is cold? Is that a clue?

Maybe the hoses warm up and make a better seal?

 Mine would stop once the engine was cold and I got over it by using a 3rd of a can of radweld.

LOLOL  I had a Manifold leak on my Oldsmobile VAN.

Was bs'ing with my Corvette/Chevy man (my brother is big in to Vette's.   He said go get come Corvette Radiator Bullets, Drop 2 in the radiator, and wait a week, then drop 2 more.   

Presto.  No more Manifold leak… I said WTH, and he said Cadillac/Corvettes  had the same issue and they
used the Radiator bullets to stop it at the factory, and are considered a legitimate fix.

On an asside, I usually had issues on the Radiator /Tstat housing until I converted it to the Metal flange.  
I also am Anal about removing and cleaning the flanges before installing new hoses.  

Jubliee Clip do weaken over time.

I have had to replace a couple for a drip drip drip.

I crawled under the steering wheel and got a better view of the area where the leak seems to be coming from and it looks like it might be the heater core after all. There's two vent openings at the back/bottom of the center console where I can see spatters of coolant, so my new theory is that the leakage I'm seeing near the hose clamps is actually dripping back from the core.

Any advice on inspecting the heater core? Aside from leaked coolant, is there anything else I should be looking for?

I had to replace my heater matrix a few months ago and the signs I had were only a slight smell when the heater was on. I had the drivers seat repaired in the winter and while it was all out I lifted the carpets to check underneath and I had some slight corrosion to the wires on the back of the gauges in the centre console and a damp patch on the carpet. I also had a drip of antifreeze on the bottom of the air distribution box but I never had any signs of leaking around the hoses. The matrix is angled downwards away from the hoses (on UK models anyway) so I'm not sure the you need a new matrix. That said, it didn't take that long to change and not too much swearing. I bought a hand pump thing from a local hardware store to suck the coolant out of the matrix before I removed it.

It has to be the heater core (aka "matrix")!

I crawled way under the dash and loosened some screws and peaked around now I'm totally sure that the leakage is coming from inside somewhere, not at the clamps where the hoses go in/out. There are drips and residue all up in there in places that cannot have originated at the hose clamps. So by process of elimination I think it means it's coming from the heater core.

So now I think I have have to get it out of there…

Question 1:
Is there a way to expose the heater core without taking it out completely. I'd rather confirm the source before doing all the surgery… but I don't see an easy way to expose the core without doing even more work to take apart much of the dashboard.

Question 2:
What's the easiest way to get the core out. Here's my tentative plan:
1. Drain the radiator spilling coolant everywhere and making a huge mess.
2. Disconnect the two hose clamps that lead in / out of the core above the gas pedal.
3. Slide the core out towards the driver side like a drawer. It doesn't feel like it's bolted in.
(see attached photo)

^ Is this the right way to do it?

Question 3:
If the core is damaged / leaking when I take it out, is there any harm in splicing the two hoses to each other and leaving the heater out until I find a new one? Obviously I won't have heat, but is there any other reason not to do that?

Disconnect the hoses on the engine side, then make a "u" pipe and joint them together there.

disconntec at the heater valve, and at the barb joint.

you can then use a turkey baster or compressed air to blow the a/f out the core.

 

This is what I used to get the coolant out of the core. I reckon it got at least 90% out. I assume you don't have Screwfix across the pond but that pump has been a useful piece of kit for other jobs as well!

Error 410 | Screwfix

Briano1234 What is the "barb join" you mentioned?

emersonthis said

Briano1234 What is the "barb join" you mentioned?

one hose out of the matrix goes to the heater valve.
the other is to the radiator hear flange via a butt-to-butt barbed fitting is usually under the heater valve.

you can replace that plastic piece with a hose repair barbed fitting 3/4 inch.

I think I understand what you're saying… If I'm bypassing the heater core I'll have some extra valves, etc in the new shortened loop of hose. If it's just a temporary thing to diagnose the heater matrix, is there any harm in leaving all those in place? Would it matter if that valve is opened or closed? I'm thinking about someone who doesn't realize there's no heater fiddling with the controls.

if you want the bypass after the heater valve opening or closing it isn't an issue.you put it on before the heater valve, it ain't going to matter.