Spring 2019 – Discovery of Heater Core Issue
[Update May ’20 below]
I discovered a few drops of some kind of juice behind the cover hood in the front of my diesel pusher. Several times over a 2 year period. Just a few drops splashed on the firewall on the passengers side of the rig but it was there every time I checked. Showed up again after washing it down and allowing it to dry, but it required driving for the liquid to show up. A bit of a sheen along that wall was also in evidence. There is also a window washer hose up in that area and since I’ve been using my washer to clean the window quite often, I suspected the juice was windshield washer fluid and that I had a leak from the small hose for that. And then I had some work done on my dash AC early in the year and the access to that is near the same area. The mechanic didn’t think it was washer fluid, he thinks it’s radiator fluid – antifreeze.
In July of ’19, drove a few hundred miles over to visit family and back to Wendell, Idaho and sure enough, just before I got to a well qualified AC shop I’d driven several hundred miles and I’d noticed I’d have to add antifreeze every once in a while. The antifreeze for this Cat engine is expensive, like $15 per gallon for the Extra Life Coolant (Red) 50/50 stuff so didn’t like wasting it. Here’s a shot of the wall below the heater core where the streaks would sometimes be wet when I’d check them. You can see that rubber hose there connected to a pipe that goes up into the bottom of the heater core. That implies there’s liquid inside the heater core, but the question is…is it condensation from the AC condenser or a leak from the heater core. I have found, unfortunately, liquid on that panel there that ‘feels’ like antifreeze, not just water. The AC tech noticed it too.
So now that I knew it was probably leaking from the heater core and that it was getting worse, I did internet searches and forum searches and that lead me to some interesting things about this problem with Journeys. Once thing is that they have screw in hose nipples (as opposed to soldered in) that are a slightly different metal then the heater core so they tend to have an electrolysis problem which ruins them and ‘welds’ them to the treads in the core. Fixing the electrolysis issue requires a ground strap connection from the chassis to the heater core. And then sometimes the nipples corrode so badly that they damage the core where they screw into it. But, removing the core requires the front end cap of the RV to be lifted or hinged out of the way for access. Hmm. That’s a lot of work. But people were saying that the nipples could be ordered and sometimes that’s where the leaks were. And the core would be fine. OK, so fingers crossed for that.
I started by buying a male to male 5/8″ barbed hose coupler. Made of plastic and only cost $1.50. Pulled the hoses off the mixer valve and looped the hot water from the engine through the coupler. Had to add 1 gallon of anti-freeze to make up what had been lost the last 300 miles I’d driven. Hmm, that sort of indicated the leak was much worse then it had been for the year previous. Drove a few hundred miles like that and it works fine. No evidence of any further leak. Simple and effective way to get more time to do some internet searching on this model RVs heater core. Here’s a shot of that bypass inside the hose loop. The yellow tape marks the input hose from the engine, the other is the return hose. The tape is important to assure the right hose goes back on in the right place on the heater core.
Took a close look at the inlet and outlet of the heater core before I’d pulled out the nipples. I sure hope it’s just the nipples…here’s one of the nipples still installed but obviously all rusted (just there to the left of that silver hose clamp).
Here’s where one of the nipples belongs when replacing. Both of the holes look good, no corrosion I could detect. Good news. The black goo is a seal. The treads looked nice and clean.
The water tracks I kept finding on the firewall don’t really give much to go on. Can’t really trace them back to any particular spot so the root cause is up in the air, that’s not surprising as the heater is only used while driving and the winds push the liquid onto the firewall. I’m just hoping that the new nipples cure the leak.
Note the rust patterns on the nipples. The threads look pretty good and there was little evidence of corrosion on them so that’s a bit worrying as it may indicate the leak might be in the core itself, but testing with new nipples is the way to go in my opinion. I suspect a new core will come with soldered stubs instead of the nipples so they’ll likely be wasted but no sense changing the core until I know for sure if it’s bad or just the nipples leaking.
Ordered the nipples from Winnebago’s service dept and 3 weeks later (yes, they are that slow) had them at hand…
I have a deep spark plug socket and found that the old nipples spun out fairly easily…it is a 17 year old heater core so they were a bit tight to start. I got lucky in that there was little corrosion in evidence. According to my reading on RV forums, sometimes they’re corroded so badly, that the core is ruined where they screw in. Mine showed rust patterns on the hose section that indicated minor leaks past the hoses but little corrosion. Here’s a shot of the hoses that connected to the nipples where you can see that liquid has been leaking by them…they wouldn’t be rusty otherwise.
So off to the parts store to get new hose and screw clamps, I wrapped the threads of the nipples with 5 layers of Teflon plumbing tape before inserting them into the core. The valve that the hoses attach to is a variable water mixing valve operated by the dash air system. The controlling air valve on the dash controls cabin heat by controlling how much water is allowed to pass through the core. It seems there’s always some hot water passing through the core no matter what the control is set at:
Checked the threads in the core again, what I could see with a strong light and magnifier, and they seem in good shape, no evidence of excessive rusting or pitting, no corrosion accumulation, so reinstalled the nipples and the rest of it…ready for testing.
Wish I had some way to charge the heater core with air or water and see if it leaks down, but I don’t. I’ll have to test it on the road. Next time I drive out for fuel will work as a test. I’ll check for water spots or streaks under the heater core to see if there’s any new tracks.
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It’s been 3 weeks since I worked on this, and I will be driving over to fuel up here in a day or two so what I’m going to do is try a fix that might do the trick. I think, based on the evidence of the rusted hose and the rust pattern on the nipples, that the core isn’t leaking but it is the hose itself right where it connects to the nipples. And how I think that happens is there is too much strain on those hoses when they’re hooked up and lashed into place the way they were from the factory. They were ‘dressed’ without regard for strain. There’s still some ‘bounce’ to the bundle of wires and hoses and I think the strain when driving down the road is too much as they heat up from the hot antifreeze and they are bouncing up and down, tugging on the heater valve which tugs on the nipples. When that happens, some hot antifreeze can leak out of the hose past the clamp, as it appeared to have happened to mine. Not much, but enough over time to show evidence of it and can seem like a heater core leak to a busy service tech.
So what I’m planning to do is get another short section of hose, another couple clamps, and a coupler, and then lengthen both hoses 9″ or so. That way there will be slack in them and I can zip tie them so they won’t move and won’t put any more downward pressure on the heat valve. That will also take the strain off the nipples themselves from the weight of the heat valve and hoses, which is where most people have a leak and or damage to the core. I tried pulling up on the hoses, which go underneath the front of the RV and than travel along the frame back to the engine, zip ties everywhere, but there really isn’t any slack there. So the extensions are the next best choice.
Got that extra hose and coupler along with a couple more clamps and here’s what I did to reduce the strain on those nipples in the heater core…simply lengthen the heater hoses around 9″ and then zip tied them so there’s hardly any strain up on the nipples.
Three days later: Drove several miles over to the fuel station I like using, far enough that the engine got up to heat. I was using the Dash Vent for some cooling in the cab as I drove and after the engine reached running temp, turned the temp control to max heat. Just a few seconds later, had full heat in the cab. It’s too warm today to keep that on full heat so I turned the control back down to cool. And a minute later, air coming out of the vents was back to outside air temp. OK, that went well, I now have dash heat again. The vacuum temp control also works so that’s good too.
I arrived at the fuel station, immediately checked up under the hood, and there’s NO evidence of a leak, which makes me hopeful that my heater core is good, no leak, and that it was indeed the strain on the hoses that caused water to leak by the nipples occasionally. Here’s a shot of that wall under the heater core case where I’d often find drops of antifreeze…this trip, none…nice and dry. Any heater core leaks drip out of that hose.
The repair is looking good so far. Just 3 days from now and I’ll be leaving on an ~300 mile trip so I’ll be testing it for much further then. I expect it will be fine, and I’ll have heat during the cool morning as I travel.
It wouldn’t surprise me in the least if all those thousands of heater cores that have been replaced on this model I’ve heard people talk about on the forums really didn’t need much more than ‘strain relief’ on those hoses going to the heater core to give them a longer life.
We’ll see though.
Nov. 22, 2019: After 232 miles on the road.
I needed to use the dash heat nearly the entire trip from Pahrump to my new parking spot below Parker Dam in California (25 miles south of Lake Havasu City). There was even snow in one area of the trip. As soon as I arrived and got set up, within an hour, I opened the hood and checked for new water spots below the heater core case. And unfortunately, there was some moisture there. Not nearly as much as I’d been finding before I did the work of installing the new core nipples, hoses, and clamps, but enough to show that the heater core itself has a small leak and it wasn’t just the nipples causing it. The engine seemed to be down by 1/2 gallon of antifreeze too. So, yeah, it’s still leaking.
Next plan of attack is to isolate the heater core from the system, attach a recirculating pump of some kind, have some kind of holding tank filled with water and antifreeze, and add ‘stop leak’ to the fluid. Let it run for an hour or two circulating the stop leak to give it the best chance at plugging the leak, then try another road trip. The alternate plan is to find out how people are changing out the heater core because it seems pretty difficult from what I know now. Involves detaching and lifting up or tilting down the entire front end cap of the RV! If I find an easier way, that would make changing it more attractive as something I could do myself. So right now is a fact finding pause in this work.
Update: May ’20
I’ve been following the sun since the spring of ’19 when this report was started and I’ve left the heater core bypass installed because it was never really cold enough to care whether I had heat or not. But I knew I had to do something about it eventually and the trip to visit my daughter in Oregon seemed like a great time. I was heading to Milton-Freewater (M-F) and the weather report indicated some coolish temps for several days along the route, some of which was in some fairly high foothills regions sporting national forests. So I left Pahrump in Nevada with it’s 80-90 degree days with the intention of reconnecting the heater core when I got further north. As it turned out though, it wasn’t ever cold enough for long enough to attempt to reconnect it on the first legs of the trip, that section between Pahrump and John Day, Oregon. It’s around 713 miles to John Day. After arriving there, I stayed over for 4 days to let the cold weather firm up on the way to M-F as the satellites showed a cold front coming into the area. It’s a nice little town and there was even a restaurant there that has great food. Until it started to rain and get cold, the weather was very nice there too. Got several projects started or completed. Much of the trip from there to M-F would be through high country which I hoped would help keep the temps low, only so the test would be comfortable. Who wants to use the heater when it’s 80 F outside?
One thing I’d noticed over the last several hundreds of miles is that I’m still adding antifreeze. Like 1/4 gallon per 300 miles. And yet the heater core is bypassed and there’s no leaks from my work under the hood that I can tell. Hmm. This could mean a minor leak somewhere else along the length of hose from the engine to the heater core and back. It’s not very big wherever it is, and it’s not in the oil pan so I’ll have to climb under the RV on my creeper and try to track it down. Might be at one or both of the gate valves on or near the engine. My last Class A there was a section of steel pipe that carried the water for a short section that had holes rusted in it that was the source of a leak, I couldn’t find it until it got big enough to create puddles under the RV.
Back to the recent trip…I had earlier bought a bottle of Hi-Gear Insta-Seal permanent radiator and block sealant. On the day I left John Day, I reattached the hoses to the heater core before leaving the RV park, then drove until the temp gauge got up to near the 1/4 mark. I stopped, shut off the engine, carefully relieved the pressure with the pressure cap and poured the stop leak into the surge tank. Then around 10 minutes of driving later the engine was up to normal temp…between the 1/4 and the 1/2 marks on the gauge…then I turned the temp control from fully cool to fully hot to start circulating the antifreeze through the heater core.
And for the first time in over a year, I had heat coming from the dash. And strangely, no antifreeze smell inside the cab like I’d had just before I’d bypassed the heater core. This could indicate that the leak has fixed itself because it was far to early for the stop leak to have circulated all the way to the front of the RV and plugged the leak. Dammit. Well, too bad, this means that the leak won’t get much in the way of the goo the stop leak is made of, but maybe it’ll stop the other slow leak. Leaks rarely fix themselves in heater cores so I suspect this seeming lack of a leak where there was one before is temporary.
Anyway, for the next 160 odd miles, I kept the temp control on high to keep circulating the stop leak through the core and I stopped several times and checked the AF level. That repeatedly came out to be slightly lower each check. So right now, I’m down around 1/2 gallon. But some of that can be attributed to the loss I had from the hoses as I tried to reattach them up under the front hood. The surge tank is slightly higher then the dash heater assembly so naturally, the AF wants to spill out the hoses. The good news was that every time I checked under the front hood I looked for any evidence of liquid splashed onto the firewall from the cores drain hose but nothing…it’s been dry the entire trip. A good sign but not definitive proof that the core leak is permanently plugged.
Looks like I will have to keep working at finding that leak. And it’s possible I have, or had, 2 leaks. If the heater core leak comes back, I’ll pour another bottle of stop leak in the surge tank and cross my fingers. As I said, I was smelling antifreeze in the cab of the RV before I bypassed the heater core, that smell is normally a sure sign of a heater core leak. But this trip, I spent an entire 3 hours driving with the heater on and no AF smell.
I have a friend with a very similar RV to mine and when his heater core sprung a leak he had it replaced at the one RV shop in Pahrump, and somehow (there’s little room to reach things) they just took the plastic case apart (I could see evidence that they used new screws on it) to access the core. They didn’t tilt the RVs front end cap which I’ve read is the traditional method. So if the leak comes back, I might just stop there my next trip through Pahrump and have them replace it instead of working on it myself since they seem to have a method. That is if this recent test ends up failing. We’ll see.
Anyway, thanks for reading. These big machines always seem to have issues like this where you can’t tell if you’ve fixed the problem or not. Or at least it’s happened to me several times over the last 16 years of full time RV living.
Update: June ’22
I am as surprised as anyone that the ‘Stop Leak’ I added to the heating system seemed to do the job with patching the minor leak I had in the heater core. I haven’t smelled antifreeze in the cab the several times I’ve used the heat in the last two years. I still use the method of slowly over 30-60 minutes increase the temp setting with the control as I drive. There is a need to carry a gallon of AF with me as it does very slowly disappear still. Not nearly as bad as before, where I’d use up a gallon topping off the tank when the idiot light showing low AF would come on over a 300 mile trip. The last few trips, I’d make it all the way to my destination without the light coming on at all and then when routine maintenance rolled around, I top off the surge tank with AF.
This last trip I took over 968 miles there were several hours where I’d need heat, and the patch worked and is still working, even after sitting for 5.5 months. Pretty happy I haven’t had to remove and replace the heater core yet. Knock on wood.