May 8

2008 Subaru Forester Heater Core Repair

Podcast2018, Subaru


Mark: Hi, it’s Mark from Top Local. We’re here with Bernie Pawlik, Pawlik Automotive in Vancouver. Thirty eight years servicing, repairing and maintaining cars in the Vancouver area and now 19 time winners of Best Auto Repair in Vancouver. Tell me Bernie, are you having to bribe people to become this best in Vancouver person?

Bernie: No, just seems to keep coming. So, it’s awesome, very fortunate.

Mark: As voted by your customers, that’s right. Alright, so we’re, enough foolery, let’s talk about cars. A 2008 Subaru Forester, what was going on with this vehicle?

Bernie: So the owner of this vehicle had experienced his temperature, his cooling temperature warning light coming on on some long highway drives. It would only, never occur around the city but on a long highway drive, a one or two hours out of Vancouver, maybe going up a bit of a hill, the red coolant warning light would click on, it’ll come on for a minute or two and go off. Just a little background on these Subarus. They always used to have a temperature gauge and some of them have gone away from that, this 08 Forester model for instance as an example. They have two lights. A blue light that comes on when the engine coolant temperature is cold, just a warning that the engine is int he warm up phase and them a red warning light that will come on only if the engine exceeds a certain temperature which is probably around 230 degrees Fahrenheit, somewhere around that range. It’s pretty hot before it’ll come on but it’s to warn you that your engine is running too hot and take action immediately. So this light was coming on and a little bit of a background story on this. A few weeks previously we repaired the head gaskets on this vehicle. He had a similar concern. We found a coolant actually leaking out of the head gaskets, so we did the head gasket repair, it was due for timing belt at the time, we did the full and complete job and he was back for re inspection on the vehicle which we do after a large major service like this to make sure there’s no fluid leaks and everything we’ve done is proper. And his only concern was that this light was coming on. So which concerned us a lot as well because it shouldn’t, certainly shouldn’t have been after all that repair. 

Mark: And what did you find during your diagnosis and testing?

Bernie: So what we found at this point, we hooked up our scan tool and drove the vehicle to see what the actual coolant temperature was doing since there was no gauge on the dash to tell us and what we found as the engine was in fact running pretty hot. Sometimes up to about 220 degrees after a while which is definitely much too hot. Pressure tested the cooling system, there was no leaks, the coolant level was full, radiator fans are coming on as they were supposed to. So clearly there was another issue and what we found in testing is that the heater core was plugged. There was very little heat in the vehicle which we hadn’t noted and the owner had for some reason hadn’t mentioned to us either. But when I quizzed him and he just recently purchased his vehicle, he said yeah there has been no heat in the vehicle and I don’t know why I never thought to mention it to us and when were warming it up, we never, I guess it was a warm day, we never actually turned the heat on to see whether it was warm or not. So anyways, that was kind of a clue, there was something going on there that the heater core was plugged.

Mark: So the heater core is separate from the radiator, is that right, that’s actually inside the vehicle? 

Bernie: That’s correct. The heater core is located under the dash and it’s a separate, its like a little mini radiator that you know, will take the heat from the engine and put it in the vehicle for our creature comforts which is pretty cool. Now most of the time it doesn’t matter if the heater core is plugged, the cooling system will bypass, but as we found out on a Subaru, actually a certain percentage of the coolant flows to the heater core and it actually relies on that coolant flow to keep the engine operating to actually dissipate the heat. So having a functional heater core or if you didn’t have one to actually make sure there’s a flow, you could actually bypass it, not that never want to, but that would actually allow the cooling system to flow properly. so having a blocked heater core actually does impede the coolant flow on this particular engine.

Mark: So what do you think happened that the heater core got plugged?

Bernie: Well actually, what we found was interesting. When we took the heater core out, you could, even actually before we took it out, so we hooked some hoses up to see if we could actually flow through it, it basically wouldn’t flow any, of sort of water but a lot of sludgy strange guck that looked like radiator sealer came out of it. So what we surmised is that previous to, this person just bought the vehicle recently, someone had probably had a leaking head gasket, they didn’t want to spend the money on it, they stuck some radiator sealer or engine block sealer or something in the system and that plugged up the heater core. I’ll just share a couple of pictures here. There’s our 2008 Subaru Forester and that is, actually for some reason I forgot to take a picture of the heater core itself, but just imagine a little mini radiator with an inlet and outlet. Well this is, we got a bucket and we saved what we poured out of the cooling system and this should a nice sort of yellowy green clear liquid but all this particulate matter and this grey colour is all from the radiator sealer that plugged the heater core. So as I, for some reason forgot to take a picture but you can see even in the inlet of the heater core, there was a lot of sludgy stuff inside there. So that’s definitely something you don’t want to see. This is an example of, this is a photograph with the dash removed of the car and the heater box out. So if you can see, there’s a bit of the steering wheel there, this shows the scope of the job, there’s the gear shifter, piece of the, part of the heater system that didn’t need to be removed and that’s basically, with the dash out.

2008 Subaru Forester Heater Core Repair
2008 Subaru Forester Heater Core Repair
2008 Subaru Forester Heater Core Repair

Mark: So obviously replacing the heater core is a pretty major job?

Bernie: It’s huge, yeah. There’s very few cars where’s it’s easy. The only cars I can think of are in the ’80s, Ford had a couple of nice heater core jobs on Mustangs and Mercury Zephyrs where you could actually open the glove box, undo four bolts on a panel and slide the heater core out. You could do it in about an hour but that’s about the only car that I remember that’s been easy. Ever since then, it’s a lot of work, especially with air conditioning and all the integrated you know, we like all those nice vents and climate control and all these kinds of things and there’s you know, everything’s built very hi tech. So heater cores are not an easy job on any car.

Mark: So is there anything else that you did to the heating or and cooling system?

Bernie: Actually we were concerned that there might be some blockage in the radiator. So we flow tested that and it was fine. So fortunately, well unfortunately, the heater fore had to be replaced but fortunately the restriction was all inside the heater core. So we did re-flush the radiator, we tested it to make sure it wasn’t blocked, there was nothing in there so everything was good but we did verify that it was all good. And after a repair, we road tested it with our scan tool and the temperature was all, it never went over about 201 degrees Fahrenheit which is perfectly normal.

Mark: So I’m thinking that the lesson here is there’s no magic goop that you should be pouring in your engine?

Bernie: Yeah that’s one lesson. Yeah definitely avoid using radiator sealer. There are a couple that are good but you really got to know what you’re doing with these things. Most of them plug up radiators, heater cores, things you don’t want to block up. So yes, as you said, there’s no magic solutions. Usually they end up creating more problems than it’s worth. I had a radiator shop I used to deal with years ago and his comment to me was, I love, I’m not going to say the name of the brand, but it was a type of rad sealer, and he goes, I love the stuff because every time people put it in, it plugs the radiator. So just creates work for him. So that’s why you don’t want to use this stuff and except under extremely rare conditions and the right kind of sealer.

Mark: And just to dig in a little bit more, in fact probably the heater core being a smaller diameter radiator essentially, saved the major, the main radiator because it plugged up that instead of the main radiator?

Bernie: It might be. It’s sort of hard to say but yeah it might just be that the tubes are small enough in the heater core that they got plugged, it’s more like the other radiator just didn’t get plugged because the tubes are larger. That’s what I would surmise. 

Mark: And so we don’t use magic goop. What was the other lesson that is to be learned here?

Bernie: Yeah, so this vehicle had just been purchased by somebody and so from what I gather, I mean, he came to us with this overheating issue and we found the head gaskets to be bad. Now had he brought the vehicle to us or to another mechanic, and had it looked at, they would have probably noted that the head gaskets were leaking and from there, they may not of noticed the heater core but they probably again, you know, testing the heating system, probably go hey there’s no heat in here, you know, your head gaskets are leaking. You might either want to walk away from this car or certainly negotiate for a better price. So again, pre-purchase inspection, have it looked at. It could save you a lot of money and grief.

Mark: So we talk a lot about Subarus. I know you’ve got one or two of them yourself, are they still good vehicles?

Bernie:  Yeah, yeah I mean they’re great cars. This is the first time we’ve done a heater core in one and we work on hundreds of Subarus. So it’s not like they don’t go bad, but it’s pretty rare. I mean really the biggest thing is that the head gaskets on the you know, from about ’99 up to 2010 somewhere  in that range, you know, they’re bad. Otherwise they’re good cars. I mean that’s a predictable problem but most every vehicle on the road has issues of some sort and other than that, they’re extremely reliable.

Mark: So there you go. If you’re looking for service for your Subaru inVancouver, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112 to book your appointment only please or check out their website there’s literally hundreds of videos, podcasts, articles on there about repairing all sorts of vehicles or as I mentioned our new Podcast on iTunes Pawlik Automotive Repair or check us out on YouTube. Thanks Bernie

Bernie: Thanks Mark

About the author 

Bernie Pawlik

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