Odd coolant leak

[little_joe]

The last 2-3 times I've driven my 40, I have coolant in some odd places/where it doesn't belong.

In the pictures below, you can see the previous owner (@upperblack) did a full cooling system overhaul and did it right - nothing around the water pump, thermostat housing, hoses, or newer radiator is leaking. There is no evidence of coolant leaking out from the radiator itself, the underside is completely free of coolant anywhere. The fan is completely dry, which makes me think it isn't flinging coolant from a leak. Cap is fully sealed, no leak; no leaks at, to or from the overflow tank.

A couple of weeks ago, I had a very minor leak at the upper hose connection to the radiator. Tightening the clamp solved that.

While it may be difficult to see in the photos, the coolant is on the underside of the hood, above the air cleaner/carb; on the top of the air cleaner; all around the carb.

It almost seems as if the system is overpressurized and spraying coolant out from ???

Obviously I could use some ideas, any comments appreciated.
Air cleaner:

Driver side:

2 from the pass side:

While running:

Each side of the carb. There is coolant all around the base.

 

[Poser]

Perhaps that rough looking heater hose on the back of the cylinder head is your culprit....



When the engine is at operating temp, are the hoses stiff/is the system properly pressurized?

 

[skully3]

this a late 70-72? im guessing its the coolant bypass hose in the back along the firewall. I swear I can see nicks in it.

 

[GLTHFJ60]

Remember at my house coolant was bubbling out of the upper radiator hose? While driving (at higher RPM) that's probably a spray. We tightened the clamp, but it's worth a check of that clamp, and others.

Get the engine to operating temp, then hold the throttle open at a "high idle" and see if coolant starts spraying out from anywhere.

 

[Michael B]

Look at the dampness next to the carb on the head. If that's not oil weeping from the valve cover gasket you may have a cracked head. I've seen that happen under the valve cover before.

 

[little_joe]

this a late 70-72? im guessing its the coolant bypass hose in the back along the firewall. I swear I can see nicks in it.

Engine is a 1972. There does appear to be a nick in that bypass hose, but...

Perhaps that rough looking heater hose on the back of the cylinder head is your culprit....

While running and revving it up, there's no spray from that hose and it's completely dry all around.

Remember at my house coolant was bubbling out of the upper radiator hose? While driving (at higher RPM) that's probably a spray. We tightened the clamp, but it's worth a check of that clamp, and others.

Get the engine to operating temp, then hold the throttle open at a "high idle" and see if coolant starts spraying out from anywhere.

Yep and the upper radiator hose is dry now/has been since I was over.

Just running it now, the upper radiator hose didn't seem to be fully pressurized, I could easily squeeze it.

 

[little_joe]

Look at the dampness next to the carb on the head. If that's not oil weeping from the valve cover gasket you may have a cracked head. I've seen that happen under the valve cover before.

Thanks for this suggestion. Best I can tell from smell and taste (not kidding), it's oil weeping out from the valve cover gasket.

 

[GLTHFJ60]

If your coolant hoses aren't stiff when running then you're nearly empty on coolant, if not empty already. Fill up the system all the way, burp it again, then execute the "high idle" test once again. Check for leaks.

 

[thebigredrocker]

If all else fails you could drive it with the hood removed and have a passenger watch for the leak

 

[Solace in Solitude]

Add Coolant UV Dye, drive it and use a UV light to see where the leak is coming from.

FWIW I had a slow coolant leak a few years back... never saw a drop, but level kept slowly falling... And temp kept slowly rising.

Eventually, a pin hole, in a brass T (I had installed in the heater hose, over the back of the valve cover) grew enough, that when I opened the hood, coolant shot about 15', barely missing my face.

I'd go the UV route, if it isn't obvious... Car parts carry 1oz bottles and $15-20 UV lights.... You can also buy dye, to trace oil leaks and R12/R13 leaks.

 

[little_joe]

Thanks all. I am going to clean things up this evening; replace the bypass hose; top it off (it was nearly full, up into the neck at the cap) and burp it. @pngunme the dye is a great idea, plus I like psychedelic colors, I'll add that then take it for spin to get it up to temp again and check hoses, pressure, and see if I can spot any leaks...

 

[thebigredrocker]

You could zip tie a rag over any areas in question. The rag will stop the spray but will be saturated.

 

[S4Cruiser]

Could it be from where the t stat housings meet? Just tossing out ideas that haven’t been mentioned.

 

[Tools R Us]

Beg/barrow/steal a cooling system pressure tester. Having it pressurized with the motor off/cold makes finding the leak much easier.

 

[reddingcruiser]

Did you check the air filter cooling coil?

 

[emac]

Freeze plug on top of head?

 

[little_joe]

Did you check the air filter cooling coil?

Yes it was good, and the square bearing spun freely. I did repot the transducer with metapoxy to be sure.

 

[JohnnyC]

Yes it was good, and the square bearing spun freely. I did repot the transducer with metapoxy to be sure.

Make sure you use the metric adjustable wrench on the bearing’s square side ... I use the bahco 8075 for finding that perfect metric size

X2 pressure tester ... they are cheap... and it gives you a good reason for buying a new tool

 

[JohnnyC]

Ohhh forgot to mention for those wondering about the bahco ... yes ... it is left handed

A left handed metric adjustable wrench

 

[skidplate]

Heater control valve and associated hoses? Just a WAG.