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Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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1999 Dodge: antifreeze/stopleak inside the core

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1999 Dodge Ram pickup. Took to the dealer to check for leaks--detected no leaks but still have very strong smell of antifreeze/stopleak inside the cab with heater and ac. also causes some type of film builldup on the windows. could it be the heater core and what are the options? what should I check for.
Sure sounds like a heater core problem from this end. Keep an eye on it around the lower part of the case for leaks onto or into the carpet, etc. If it is the heater core, it will only get worse, not better. Only sure cure is to replace it, which on your rig is a big job, means removal of the dash panel etc.
Customer: replied 10 years ago.
Hi Bob,
If I detect no leaks inside and the dealer detected no leaks inside; and I changed the radiator cap, what else do you think it could be?
My only other concern would be if the unit is AC equipped, to check for a possible plugged AC drain on the outside of the heater case. It may be that you are smelling only fumes, but the fact that you are getting the fog on the windshield would be enough to make me worry about the core having a leak. It's really too bad it isn't more accessible so a guy could get a good look at it. Rest assured if the core is bad, you will be sure of it soon enough. As I said, the film on the windshield can't come from very many places. Regardless, it is sure worth keeping an eye on. Let me know how you make out.
Bob and 5 other Car Specialists are ready to help you
Customer: replied 10 years ago.
Relist: I still need help.
should not have accepted yet. do not want to pay more but smells when in AC or Defrost mode and doesn't seem to small when using the two settings that do not run the evap.
Really don't understand why that would make a difference? The AC also runs anytime you use the defrost mode. Please do NOT hit the accept button again, we want it fixed for you as much as you do. In AC and defrost the only difference is that the AC compressor is engaged and your mixing cold air with hot air.. Have you had the system pressure tested and checked for leaks at the AC drain and or around the heater case?
Just a thought, but some AC systems will develop an oder that smells like a swamp, due to bacteria forming on the condenser and such. Have you tried a spray deodorizer inside the duct system to see if it changes anything? I also wonder if maybe you are smelling something other than antifreeze? Maybe hot plastic or something else? Is the windshield still fogging up. That in itself is reason enough to have concern about the heater core. Just some more thoughts I thought I would pass along. I understand your concern and again think maybe a good pressure test and inspection of the evaporator drain and lower part of the case may be a good idea. If it is only a very slight leak it may be difficult to locate or even see for sure that there is a leak. Have you had to ad any coolant?
Customer: replied 10 years ago.
Thank you Bob for the great and thorough follow-on. I smell what seems like a mix of antifreeze and stop leak is almost toxic at times. I drive with the windows down unless in the settings that are not AC or Defrost. My dealer did a complete pressure test and found no leaks. I am happy with your responses but am confused.
Hate to admit it but I am confused also. It would make sense that if there where a core leak it would not matter if the AC was being used or not. Do you know off hand if your trucks heater system has a hot water shut off valve in the system. This would be a fitting in the heater hose with a vacuum line attached to it. If so, that may explain why no smell with the AC. If the valve shuts off the hot water or coolant flow when the AC is turned on. Then I would still be concerned about the heater core, but if they can't find a leak, it is going to be pretty hard to fix until it gets bad enough for someone to see it when under pressure.
Customer: replied 10 years ago.
HI Bob,
The smell is definitely there with AC and Defrost but not the settings with just arrows (in my Dodge, as you probably know, the AC has a snowflake and the Defrost has a windshield symbol). The settings without those icons do not smell, just AC and Defrost. I know it seems strange. I think I am going to park it for awhile then take it back to the dealer for another look.
Pat Murray

Hi Pat,

When you get a chance look at the heater hoses and see if it has that shut off valve, That would explain why no smell at certain times. Please let me know when and if you get it figured out. I still have a strong suspicion about the heater core, but I have also been wrong more than once. I sure wish you well with it, if I can help further, just yell. If I don't talk to you again before, Happy Holidays to you and yours. Smile