Coolant Leaking Into Passenger Footwell After Heater Core Replacement

[jhay]

Hello all. So here's the story...

...replaced my heater core Friday afternoon on my 171K '95 850 GLT non-turbo, after spending hours of research on Volvospeed and elsewhere online. Took me less than an hour due to the wealth of info, which I'm very grateful for. After replacing the heater core (and the o-rings which go into the heater core), I slowly poured in a whole bottle of coolant into the reservoir, and jumped and shouted joyfully when I saw the heater core was no longer leaking.

Turned on the engine and let it run for about five minutes with the cap off the tank to get the air out; replaced the cap and drove around the neighborhood a few times just to check that everything was okie dokie and to enjoy a console free of the ominous cooling system warning light (nothing was leaking, coolant level stayed constant.) Ran the heat just to check--got a whiff of coolant for a little bit, but it went away, which I was content with. Ran the A/C, and it worked fine and didn't have the coolant smell at all. Got home, spent some time getting started on cleaning the coolant out of the carpets, and then had a fitful rest, dreaming of no longer having to deal with wet floormats and coolant vapor.

Got to the car Saturday afternoon to go to work--started the car, and that red warning light was back. "What the (insert expletive)?"

Turned off the car, popped the hood, and saw that the reservoir tank was empty. Confused, I went back to the cabin and pulled the driver side carpet back up (I had not replaced the plastic trim panels yet) to check for a coolant puddle like before...but there wasn't one. Walked around to the passenger side and saw, to my chagrin, a new coolant puddle, though no where near as much as a whole bottle's worth (maybe a cup or two--I had left the carpet pulled up, so the new coolant couldn't have soaked into the carpet.

Threw in some shop towels to mop up the puddle, then poured in some water into the tank to see if if the connection to the heater core had sprung a leak...nope still good. I double-checked under the car, and the hoses in the engine compartment, and could not determine where the leak is occurring.

After searching the forums, I saw some talk about the heater core coupler and about replacing it at the same time as the heater core. However, if the coupler is the problem, wouldn't the coolant have leaked into the driver's side (from the schematic attached it's supposed to be in the region of the driver's side pedal, correct?)

From the same schematic, the only thing on the passenger side is the A/C evaporator, correct? What's the likelihood of that failing about the same time as the heater core? When I first noticed the carpets getting coolant in them, the passenger side always had more, but I diagnosed it as the heater core since it was leaking onto both sides (along with the myriad of other systems conducive to a heater core failure.)

I'm a proud DIYer, but replacing the evaporator does not seem as easy (or as inexpensive) as replacing the heater core. Any other ideas? Going to a shop is not really an option because I'm playing the poor college student card, and relying on the wife's Scion while my Volvo sits in the driveway is not an enjoyable thought either.

Thanks for your time, and I look forward to your advice!

[tca217]

You didn't say if the water that was leaking on the pass. side was coolant for sure or not, but I am guessing it was because you said that the res. was empty. So I am thinking maybe you have a leak in the core or the hose connections that is small enough that you didn't notice it but still was leaking and the coolant came out of the overflow hose that comes from the heater core housing. You should be able to see some kind of flow pattern to point to where the water is coming from and then just back track to the problem. Just an idea, hope maybe it will help....................TIM

[--Aaron--]

Did you use Genuine O Rings? Aftermarket ones can cause problems. My other thought is that you may have damaged the coupler while either uninstalling or reinstalling, it is very easy to tweek the hard lines running from it to the core. Tweek the lines enough and I imagine it could cause coupler problems.

[(n)A-GAME]

Check the O-rings. And no, it wouldn't necessarily leak to the driver's side. Just depends where the fault is (there are two lines).

[jhay]

Okay, so I'll go check the coupler, since I do remember having to move the hard lines a little bit to reconnect them to the core. The heater core o-rings are good. I'll also double check it's location in relation to the passenger footwell, since that's still a confusing point for me.

[Gilhuly]

A couple things that time will sort out: Is it water or coolant? White paper towels will sort that out. Secondly, it is not unusual to have coolant drop the first day or two after refilling the system when you don't have any type of vacuum system for filling. An alternative problem could be a clogged drain for the A/C evaporator (if it is water). I wouldn't jump to the,"the o-rings are fine" conclusion unless I've verified it visually. Green ones? Uh oh...

[(n)A-GAME]

Yeah, exactly - green, run away, LOL. All I had on hand when I did mine was aftermarket ones so we had to double them up to stop the leaks!

[AverageVolvo]

Order a New Heater core coupler from Fcp(bypass it in the meanwhile), it comes with the o-rings and yellow clips as well.

It's VERY common to damage the coupler I usually install a New one @ the same time as the heater core, and new hoses as well.

[jhay]

Hi again. Sorry for the sporadic posts--went on vacation the past week. Anyways, the story continues...I went to the driver side and began looking at the heater core coupler. Had a couple thoughts after looking at it:

First thought: "What the heck am I looking for?"

Second thought: "No one on the forums responded to my thought that the coupler is on the driver's side, but the new leak was only on the passenger side."

Before ordering the coupler and getting my mind into a repair mode, I had one more thought: "Why not test it again?" Everything had dried out since I was last in the car, so I thought that would make it easier to trace where any leaks would be coming from.

I placed paper towels (to check for color) and shop towels on the floors of both compartments, and doubled-plastic bags directly beneath the heater core to catch any leaks. The reservoir was completely empty, so I filled it with 48oz of just water, since I didn't want the extra worry of having to clean up more coolant if the leak was still present.

After pouring in the water and hoping/wishing/praying a bit, I checked both the driver and passenger floors and was surprised to see dry floors. I started the engine and ran it and the heater a bit--still no leaks (still smelled the coolant when I turned the heat on, but ever so briefly.) Took a test drive around the neighborhood with the paper towels and bags in place--nope, no leaks. Awesome.

Of course, this was the case after I first replaced the heater core, so I am still not convinced that it's a done deal. Will let the car sit for ahwile and will report back tomorrow to see if the same leaking happens (with the towels and bag in place.)

Something curious: I checked the reservoir after my brief test drive, and it looked like it was filled with a perfect mix of coolant & water. I guess wherever the unknown leak was from didn't allow all the coolant to drain from the system. Right now I'm gonna go with tca217's explanation; if not, and the o-rings are bad, then it'll leak into the bag, which will affirm everyone else's thoughts. Both lines going to the core are almost entirely on the driver's (left hand) foot well, which led me to originally dismiss anything leaking regarding those components.

[Guest jhay]

Fixed, I believe. The coolant level dropped some more yesterday, but it wasn't leaking inside or outside, so I assume it's just bubbles. All in all, it's back to how it used to be, and I don't have to worry about my engine melting to death.

FYI: Was able to get rid of the coolant smell when the heaters first came on by using forum advice: heaters full blast with the windows down to dry out any coolant in the vents.