Subaru Outback heater/antifreeze leak issues

I have a '97 Subaru Outback with 160,000 miles. I live in Minnesota.

A week ago on my commute to work I noticed after most of the 18 miles, when I stopped at a stoplight it started blowing cold air instead of hot into the cabin, and the temp gauge started going up. As soon as the light changed and I accelerated, everything returned to normal.

At the next light everything was fine. When I stopped in the parking lot at work it happened again.

I shut off the engine and called my mechanic. He said it sounded like the AF was low and not getting into the heater core unless I was accelerating and to get it to him asap.

After work I drove 2 blocks to a service station and added just a small amount of AF to the radiator. I noticed the resevior tank appeared to have little in it. I drove it home, and the next morning to the mechanic. In that time the problem didn’t repeat itself.

He purged the air from the heater core, and did add about a quart to the radiator. He said he tightened a couple of clamps where there might have been a small leak. He warmed it good, pressure tested it and test drove it, and all was fine.

I picked it up and it worked fine for the next couple of days driving to and from work.

Yesterday I decided to take about an 80 mile trip. It’s cold outside if that matters. 0 degrees and below. About 10 miles in I stopped in stop and go traffic and the initial problem repeated itself briefly, and then all was fine. I watched the temp gauge closely for the rest of the trip and it stayed in the exact spot it always does, so I was hopeful.

I was a little late, so I was driving pretty fast, at times up to 80. About 60 miles later I pulled over for just a brief stop and when I did I noticed the temp guage went right to the top!

I don’t recall, however, that any cold air was being pumped through at this time.

I drove next door to a service station, bought another bottle of AF just in case, and filled the radiator. I got in maybe a pint to a quart. I noticed AF had splashed around the engine compartment, and seemed to radiate out from around the resevoir or radiator cap (they are close together). The resevoir was FULL.

Also, I know you are not supposed to remove the radiator cap when the car is hot but I was in a hurry and had to. I grabbed some towels to cover the cap and was surprised that only a small spurt came when I loosened the cap. I expected more of an eruption. As I filled, I noticed quite a bit dripping down under the car, but that slowed and seemed to stop, even while I filled.

I drove the final 10 miles or so to the hockey game I was attending, and then after the game came out and refilled the radiator, which was down again. I didn’t notice anything leaking, but there were just a few drips that had dropped down while the car sat idle.

On the way home I watched the temp needle closely and it never moved. I did feel the heater pumping out super hot air after a while, maybe 50 miles, so stopped and refilled the radiator again. Same deal. AF splashed all around, and some leaked while I filled but that seemed to slow or stop.

I stopped 2 additional times to refill on the final leg home. When I was 2 blocks from my house driving slow through the neighborhood I noticed cold air getting pumped again, and the temp gauge started rising for a moment or 2. I parked the car outside and plugged it in so I wouldn’t get the fumes and mess in the garage.

I’ve been planning on replacing this in the next months anyway. Do I fix this problem now? Or do I trade it in and take whatever they will give me for it???

If the engine coolant was hot when the radiator cap was removed, there should have been some pressure built up to where coolant should have shot out the radiator. That’s why you’re warned against removing a radiator cap from a hot engine. You can get scalded.

The problem might be due to a defective radiator cap. If the radiator cap isn’t capable of holding the proper pressure, coolant can escape from the cooling system as a vapor. At this point, have the radiator cap pressure tested to see if it holds the proper pressure. Or just replace the radiator cap with a new one to see if this solves the problem. Afterall, they’re not that expensive.


Thank you. I should have commented that the next time I removed the cap “hot” I got a pretty good spurt out of it. I had been wondering about a faulty cap until that point.

I was able to determine the fluid (at least any at the top of the engine) was spurting out of a small relief hole in the top of the resevoir. I found this out when I started unloosening the cap, and before it was totally loose, fluid would spurt through this hole. I repeated this a couple of times to verify. But it appeared to be spurting out of there while I was driving as well, because it had splashed out of there prior to my noticing where it was coming from.

The year of your car was within the window of some head gasket problems for Subaru’s. If the gaskets have not been replaced and are going “south” A condition pressureizes the cooling system with air and forces the coolant out thru the over flow. Its also possible it could be intermittant!! MHO!!