I've recently purchased a 94 850 wagon (N/A). It has symptoms of a leaking heater core... Coolant smell inside, windshield fogged up a bit when I first got it and it is losing coolant (approximately one pint in a hundred miles). Before ordering parts, we opened up the trim panels to access the left side of the heater box and there is no sign of any leakage. We took the evaporator drain hose loose from the heater box and no coolant leaked out. The pipes going to the core appear to be in good condition. I've checked the car thoroughly for other possible coolant leaks and there are none. The system holds pressure enough that two hours after shutting off the engine it's still holding some pressure when you remove the cap. As I said, the symptoms all say heater core but where in the world is the anti freeze going?... (No sign of head gasket issues either)

 

Hey Casey, there is no drain for the heater core. The evap drain will drain off water from the AC, nothing to do with the heat side.

The core will leak and will likely come out of the seams of the box. It usually leaks immediately into the carpet insulation and maybe some even evaporates, thus the steam on your windshield.

You see the symptoms, take action before you BLOW the core and RUIN the motor by overheating it trying to make it somewhere without coolant.

Collant leanks and broken timing belts are the #1 and #2 reasons these cars leave the road.

 

I don't have an issue with replacing the heater core. In fact, as heater cores go, it looks like a rather simple operation. My only concern is verifying the diagnosis. I have added an entire gallon of coolant in less than a month. I can assure you that the exposed part of the core on the bottom of the heater box is completely dry (albeit brown from heat) and at least on the driver's side, there is no fluid at all under the carpet. I didn't realize that the heater box was divided between the heater and evaporator cores so I suppose the missing coolant could still be in there. The old Audi's that I used to work on would dump antifreeze out of the evap drain when the core went bad... If it is sealed that well I'm sure not looking forward to the green shower when I open it up. It just doesn't appear to me that there's enough space in that heater box to contain that volume of liquid and still have a functioning heater. I really hope that you are correct and it is only the heater core but I think I'm going to do an exhaust gas check in the cooling system before I go any further to make sure I don't have a combustion leak first.

 

If you need to get your hands on one I know autozone has a loaner kit. The fluid you need to purchase but the block tester you get your deposit back on.

Remember to check the heater hoses, upper and lower radiator hoses and even the thermostat housing. I installed a new lower hose when I did my heater hoses and I know I still have something seeping as I'll see some antifreeze down at the low end of the hose.

 

Well, if it's steaming your windshield and you smell coolant, you likely have a heater core issue.

Now, that may not be your only problem, remember, you are talking about a 19 year old car. You can read this thread and see if it helps you:
https://volvoforums.com/forum/volvo-...roblems-63516/

 

I would suggest a cooling system pressure leak down test:

1. engine cold; pressurize the cooling system to 1 bar (~15 psi) and let it sit overnight.
2. then in the AM, ck the pressure; perfect is no pressure drop from previous evening.
3. Assuming there is some pressure drop; ck everywhere for external leaks (esp around heater core since you got vapor on interior of windshield) and repair as necessary.
4. If you do have pressure drop, but no external leaks found, then with the spark plugs out, crank the engine (disable spark and fuel) while you observe from engine bay; see any gushers, then there's your leak/problem..

 

Not to hijack a thread, but no sense starting another on a similar issue.....any thoughts on what would cause a coolant smell from the heater vents, but no window steaming or loss of coolant?

 

Well hopefully mine is fixed... After verifying that the heater core was good I was thinking the worse but upon further investigation I found that the seam between tank and core on the right side of the radiator was leaking just enough to spray into the fresh air intakes when the radiator fan turned on. New radiator installed so hopefully no more leaks. Apparently that was enough for the interior odor. As far as the stuff on the glass, it may have been nicotine or something else... As I said, I just purchased the car so that may have been there awhile... No gas in the coolant btw.... Thanks everyone... I'm sure I'll be spending more time with y'all..

 

By design it's almost normal to get a little whiff of coolant odor here and there. There are 2 seals at the base of the core that leak a little sometimes.

Every leak has a start and a finish. The start of a heater core leak is likely minor and progresses to major and failure. I'm not sure how long they leak before they start fogging a windshield and leaking coolant all over the place but if the odor last longer than a few seconds, be concerned.