Please read the original post on the above subject that was placed on Oct. 30th. I felt it would be prudent to share an update. I've completed three pressure tests on the car's cooling system. The system didn't hold pressure on the first test. After a complete search for visible leaks, I identified one at the bottom of the upper radiator hose and thermostat housing. The system still didn't hold pressure on the second test. After tightening all of the hose connections on the car, the results of the third test were accepatable...pressure held steady for a good period of time with no signs of visible leaks. The 15LB cap was also tested and results FAILED. The last thing I uncovered was the suction hose was laying on the bottom of the overflow reservoir (not sure what part this would have played)? My comment about the moisture in the original thread, which I noticed on the underside of the floor mat, may have been what threw me or others off. I had mentioned how there's a tremendous amount of heat generated on the underside of the passenger floorboard...covered by carpet, and further by a clear plastic floor mat. Now with the above pressure test results, I'm thinking that what I noticed, which only occured once, were conditions that caused some condensation to form on the underside of the plastic mat (next time it gets the taste test). Never...did I notice any film or moisture on the windshield with the heater on and in the defroster mode. The smell of coolent was mostly noticed after the car had been driven 5 or more miles and when I was exiting from the highway (pressure buildup?). With all of this subsequent investigation, I'm now thinking that the smell I was getting, was coming from the engine compartment, through the air vents, resulting from a burping from the radiator, allowed to happen by the failure of the radiator cap. Based on all of the above, I'm planning to go with the acceptable pressure test results and will not be replacing the heater core. Hope this is helpful to others who may have had a similar experience.
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Re: 1974 Heater Core (follow up)
In my limited experience, I have learned that a 25 year old heater core will most likely fail sometime within the next 5 years. I would recommend replacing the heater core as a preventative maintenance event rather than wait for a failure that will probably occur at an inconvenient time. In my case, it failed 5 days before a PV test! It was a panick but we " got er done". In preparation for another PV test on a '74, I replaced the original heater core with no leak indicated and found that the core was showing early signs of failure with a leak likely in the near future. -
Re: 1974 Heater Core (follow up)
The heater core in the car today had been replaced in 1997 during its restoration.Comment
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Your comment that
the suction hose in the reservoir tank was off might be the biggest clue.
What can happen in this mode is that coolant will flow to the tank when the engine warms up, as designed. After shut down, the coolant cannot return to the system due to the missing hose, but the system will suck air instead. This will leave the radiator with a certain 'headspace' of air, instead of being 100% full of coolant as it should be. During each subsequent cycle of operation, more and more unrecoverable coolant is discharged to the tank until the system reaches equilibrium and then burps steam instead of liquid coolant. Due to the reduced coolant level, and exacerbated by the faulty radiator cap, the engine will tax the capacity of the cooling system and eliminate any sort of 'boil over' margin that it may have normally had.
A routine shutting off of the engine (inducing heat soak effect ) or reduction of cooling air flow (exiting the highway) may now be enough to cause a boil over effect in the radiator, expelling steam into the reservoir.
It is probably this steam you were smelling under the hood.
This obviously has nothing to do with condensation under the floor mats. That's probably normal C3 leaks from around the t-tops or windshield frame.Comment
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