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Beware of Thermex brand front heater core
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Fogerty1970
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PostPosted: Fri Feb 03, 2017 10:44 am    Post subject: Beware of Thermex brand front heater core Reply with quote

I got quite a bit of dash pulling practice in the past 10 days. Three times to be exact. To avoid making this an opus you can find my original issue here: http://www.thesamba.com/vw/forum/viewtopic.php?t=671397&highlight=

I am pretty sure there is a flaw in the Thermex (by Dansk) front heater core design. I purchased the thing from AutohuasAZ for about $100. Anecdotally, I have spoken to a few others who ran into the same exact issues I did --- namely, an inability to purge the unit of air, and subsequent lack of heat emanating from the unit. Mine never heated uniformly, after hours spent bleeding the system per the Bentley methods and other ways described on this forum. At my wits end after Dash Pull No. 2, where I sought to determine if I had screwed something up (how can you, it's 2 hoses), I took it to a 30+ year VW tech in town who is a Vanagon expert. He bled the system and wrote this succinct note on the receipt: "bled heater core/cooling system. Still no heat. Bad heater core."

In the end I found a good uses core on eBay, did Dash Pull No. 3, and threw it in. With the heater box top off, I bled the system, and felt the unit heat up right away. Now I have heat to spare. Like lots of heat. The thing practically bled itself, but I did fill it with coolant before throwing it in, per Dhaavers suggestion.

So let's do an autopsy of the Thermex unit and why I think it leaves much to be desired when comparing it to the OE core.

First off, a side-by-side comparison:

Image may have been reduced in size. Click image to view fullscreen.


The VW unit has much beefier fins, is slightly larger and much sturdier. You cannot see through the unit. But you sure can with the Thermex. Take a look at how thin those coolant lines are running through the unit:

Image may have been reduced in size. Click image to view fullscreen.


Now let's take a peek inside the piping to see the size of the passageways. First off is the Thermex, note how small the lines are:

Image may have been reduced in size. Click image to view fullscreen.


And now a look inside the OE core. The lines are substantially larger:

Image may have been reduced in size. Click image to view fullscreen.


The difference in size makes bleeding one easy, the other a 6 (or 12) pack headache. I am not an expert on fluid dynamics or the various aspects of thermal transfer in heating systems. I am just a man trying to keep his beloved van alive. Perhaps I was close to getting the thermex bled. Maybe I could have spent hours more on this thing. Maybe I just got a bad core. All I do know is that the brand new core was too much of a hassle to deal with, while the 30 year old used unit worked well and immediately. A properly working core in a vanagon should put out a lot of heat. They are relatively huge.

This from member "iulian," who experienced the exact same issue with the exact same core: "My guess: production fault when sealing the inner space between inlet and return pipes, allowing coolant to flow directly into return line(the path of least resistance) without passing the core tubes first and only allowed coolant to flow through when the pressure built up on high revs."

He could be on to something there.

When you consider the involved nature of a dash pull, you want to know that what you are installing is going to work. I know the aftermarket is thin on some parts for our vans. I know bleeding a van can be a hassle at times, and i know there was a time when cores were not even being made, but for future reference, IMO it's buyer beware when it comes to the Thermex heater core.

IF anyone else out there has had similar bad luck with these cores, or if there is an engineer who could surmise as to why the thermex is so hard to bleed air out of while the VW unit is a veritable walk in the park, please feel free to chime in.

Meanwhile, I am gonna enjoy my newfound heat from an old ass core.

Chris
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Slimvest
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PostPosted: Fri Feb 03, 2017 11:38 am    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Interesting info. Sorry you had to deal with three dash pulls!

I have a supposedly good used heater core that I was nervous about installing, but maybe OE used is better than this "new" replacement option.

Maybe a quick pressure test of my used core and then I'll start the work installing it.
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PostPosted: Fri Feb 03, 2017 12:03 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

I need to replace my core too. Between this story and the general shoddiness of new OE parts I'm going to wait until GoWesty's new design hits the market and decide between that or the one Terry Kay sells. Both claim design improvements and higher quality materials.
In the meantime I have the flow to the front core completely shut off. Gonna be a cold road trip on the way to Baja! Crying or Very sad

GoWesty:
The design uses flat tubes which are more efficient than the stock round tube design. Additionally, the overall air flow through the core is greater and the use of copper fins increases the heat transfer efficiency for better flow AND more heat.
Features:
• Made in the USA of 100% USA parts
• Brass tanks
• Tellurium copper fins
• Galvanized steel sides
• Individually pressure tested

Terry Kay:
83.5 to 91 Vanagon Front Heater Core--NEW!`
Here's a brand new custom made Vanagon front heater core that has been not available anywhere for some time --not at VW, Not at an Auto Parts Store.
The part is No Longer Available.
These cores are a big improvement from the stock core are designed and devloped by me.
The have a larger core tubes, and flow more air over them offering bigger BTU's in the cab of the Vanagon .
They have copper cores, and steel tanks for a longer lasting, trouble free performance.
It's a neat update for your worn out front heater box & core.
$279.00 plus shipping
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jeffsab
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PostPosted: Fri Feb 03, 2017 12:09 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Fogerty1970 wrote:
I took it to a 30+ year VW tech in town who is a Vanagon expert.


Kind of off-topic, but who did you take it to? In K'zoo?
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PostPosted: Fri Feb 03, 2017 12:10 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

I appreciate the research you've done and this post. Dash pull is in our not to distant future and be great to only do it once! Thanks!
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PostPosted: Fri Feb 03, 2017 12:15 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

I have never needed to purge air from the exchanger, I guess the pump pushes it out naturally. Not even sure why people say its necessary, unless it means your pump is weak.
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PostPosted: Fri Feb 03, 2017 12:28 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Good info for the collective.

FWIW/just to provide another perspective, my new Van Cafe core worked great
right out of the box (as I posted in your other thread). Money well spent.

Thermex looks like more of a "parallel-flow" design...??? Looks similar to the
construction of my new AC condenser (which works great, BTW) but maybe
not great for a heater core...???

Disclaimer: (Also NOT a fluid dynamics engineer...) Wink

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Fogerty1970
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PostPosted: Fri Feb 03, 2017 12:39 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Will be interesting to see what the GW unit looks like went t hits the market.
On the water pump -- its an ej22 engine and I replaced the timing belt with all new pulleys and new OE water pump in Nov. So I doubt it's the pump.
I have no doubt that Terry Kay's core is a good one. Sounds like he has them professionally made. But I am on a budget and can't afford it right now.
I have no qualms installing a good, pressure tested used core into a van. I think it's a very good design and from all the research I have done should last a very long time given that coolant is consistently flowing through it, even in the summer once in a while.
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Christopher Schimke
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PostPosted: Fri Feb 03, 2017 12:46 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

http://www.thebrassworks.net/shop/Heater-Cores-Oth..._info.html
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dhaavers
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PostPosted: Fri Feb 03, 2017 2:05 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

^^^ Whoa...spendy-riffic! Shocked Certainly looks bulletproof, though.

Oh, well...it's only money...<shrug>

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PostPosted: Fri Feb 03, 2017 2:38 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Fogerty1970 wrote:
Will be interesting to see what the GW unit looks like went t hits the market.
On the water pump -- its an ej22 engine and I replaced the timing belt with all new pulleys and new OE water pump in Nov. So I doubt it's the pump.
I have no doubt that Terry Kay's core is a good one. Sounds like he has them professionally made. But I am on a budget and can't afford it right now.
I have no qualms installing a good, pressure tested used core into a van. I think it's a very good design and from all the research I have done should last a very long time given that coolant is consistently flowing through it, even in the summer once in a while.


I am on my original core, 31 years of use. coolant has been serviced regularly since new. of course a used core may already be that old and may have suffered neglected maintenance, and be a ticking time bomb, mine might be a ticking time bomb, both may test well, who knows, then we have all the suspect issues of low quality new build stuff, or unwillingness to pay big bucks for all new quality parts. Lifes full of risky gambles, less so if you can pay the price for better odds Crying or Very sad Crying or Very sad Crying or Very sad :cryma a gambler should weigh the odds verses the loss per gain. the loss if one looses the gamble is having the nightmare replacement job to do, (it goes faster the second time), plus the second purchase. This is weighed by verses the gain of saving, $75, 100, 200 by purchasing the suspect part verses the higher quality pricey part.
The easier the part is to replace, the less likely it is a fatal failure, the more risk tolerance I have so a cheaper part may suit me. if failure is a trip stopper (ie tow home) and very labour intensive, the less risk tolerant I am and thus more willing to pay more if need be for the quality part.

I would save the money on less risky stuff than the heater core, so used units for me are out of the question pretty much, Id be temped to turn down a free used core for install, but that is my risk tolerance.
I may even end up replacing my working core with new quality part, just becuase I need to tear into the dash anyway for another issue, blower lube dried out. I only want to do the dash removal thing once in my life, and plan to have the van a while, so rather spend the dough on new quality part now, rather than wait for failure, and have to do dash removal again. (or just live with no blower till the core leaks and I HAVE to remove the dash, thus risking failure on a long road trip, vacation spoiled, expensive tow home, again the risks and gain verses lose is wieghed, oh the risks of taking risks.

1...Now why the replacement core did not bleed well I dont know, perhaps it can be prefilled with water, ports pluged with rubber stoppers until hoses attached, there should be minimal spillage Id think with the right technique. hoses would be pinched closed until ready to fill rest of system to prevent loose of water from core thru dry hoses.

2...otherwise burp the core of air by lossening the high hose while running water with a flushing tee (Prestone Flush and Fill kits) thru the cooling system, that should purge it of air. but you might get a bit wet, so use clean water not antifreeze. youll need a helper to control the water flow as you crack the hose to vent the air to minimize spillage.

3. And one last thought, you dont have the coolant flow backwards do you, either hoses swapped at core, or maybe further back along heater hose, coolant distribution tower on motor???? I would guess if the core flow was reversed that could effect ability for it to self purge itself of air. so crawl under the van and trace the hoses, compare them to that in bentely book, if they are swapped some place, that might be the issue.

Good luck Shocked Shocked Cool Laughing Wink Wink Laughing Rolling Eyes Laughing Rolling Eyes Laughing
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PostPosted: Fri Feb 03, 2017 2:42 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

dhaavers wrote:
^^^ Whoa...spendy-riffic! Shocked Certainly looks bulletproof, though.

Oh, well...it's only money...<shrug>

- Dave


Bulletproof yes, but only if you use distilled water and the proper coolant. Brass/copper and aluminum in the same cooling system creates an anode/cathode corrosion system. Ask me how I know!
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PostPosted: Fri Feb 03, 2017 3:21 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

My understanding is that an anode/cathode circuit can only be complete if there is BOTH an electrolyte joining the two metals (e.g. very old coolant) AND a second electrically conductive path that is not through the electrolyte. Given that the heater core is insulated from any other metal parts of the vehicle by the plastic of the heater box and the rubber of the heater hoses, I do not see how the circuit could be completed.
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PostPosted: Fri Feb 03, 2017 5:06 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Wont the plastic pipes corrode the brass, or was it the stainless pipes corroding the coolant distribution tower, or was it the hose? Will holy water fix it?, what about subaru conditioner?


On a side note...

I have been looking for three weeks for the clutch cable nut to adjust, do I have to move the shift lever out of park to expose it?


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PostPosted: Fri Feb 10, 2017 12:20 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Look what just popped up!

http://www.gowesty.com/product-details.php?v=&id=24611
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Terry Kay
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PostPosted: Fri Feb 10, 2017 12:56 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Not innovative at all, just capable of duplication, and at a higher cost to boot.

Pitifuly late too.

Not at all impressive.
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Fogerty1970
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PostPosted: Fri Feb 10, 2017 6:41 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

FWIW I just received a refund from AutohausAZ this morning for the horror core air bubble trapping device.
From my research I am not the only one getting money back after returning these (imo flawed) units.

And, yea, wowzahhh --- three-hundo for a core?! Undoubtedly there is some R&D cost added in there, but for heaven's sake, you can score an OE Behr radiator for half that much.
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PostPosted: Mon Nov 27, 2017 9:53 am    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

This heater core is also sold under the brand "Classic Line". Says thermex on heater though. Put one in on a new subaru conversion and thought it must be that. Spent 7 hours myself trying to get it to make heat. Finally fave up and brought it to a shop which spent another 4 hours. They couldn't make it work.

Put in gowesty one and it made heat right away. No bleeding issues. &*(^&*&*(

The gowesty one was cheaper than 4 hours of shop time and worth my lost time doing a dash twice. Grr. One whole Saturday along lost to doing the job again.

If you try and use one, test it first in the sink with hot water to make sure it actually works. I'm sure some of them must work.
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PostPosted: Mon Nov 27, 2017 9:58 am    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Just put in the GoWesty one myself. Works great so far.
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Mellow Yellow 74
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PostPosted: Mon Nov 27, 2017 12:55 pm    Post subject: Re: Beware of Thermex brand front heater core Reply with quote

Terry Kay wrote:
Not innovative at all, just capable of duplication, and at a higher cost to boot.


Current prices - TK $279, Gowesty $199
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