cleaning heat exchangers 72-74

[BusBerd]

I am embarking on cleaning and hopefully doing some repairs on my heat exchangers.

I have researched a ton of threads on samba as well as other sites and also reviewed my various repair manuals. As you can see from the photos below, I already have them apart (I have always been bad at remembering to take the "before" pics on my various projects.) They are not in terrible shape. But since my engine is out, and I have time while waiting for some other parts to come in, I thought this might be a good time to work on the heat exchangers.

I will take new photos of their current state and I will try to document my progress going forward.

Currently I have them apart, as I said, and I have soaked the actual exchangers (without the shell) in my parts cleaner for a day. I was hoping to clean out the inside of it, with all of the black exhaust carbon deposits in there (is it "carbon deposits"???), but that was not successful. I have read that I should not get media from a sandblaster into the heat exchangers. I am not sure why that is. will they clog? What does it look like in there? Is there any way (or any benefit to) clean all of that black carbon deposit off the entire inside of the exchanger?

I have cleaned the shell of the exchangers too, in the parts washer. Thats much easier, of course. I have sandblasted one side of one of the heat exchangers already and I will finish the rest as I have time. There is minimal metal repair, so I am hoping to have simple hole-pugging welds rather than have to fabricate fitted metal.

I am replacing the asbestos with this: https://www.amazon.com/gp/product/B0051UPAK4/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
But I am not sure yet what to use in place of the thin tin-foil like stuff between the insulate and the exchanger. I have read that some have used a pizza pan from the dollar store. I may go take a look. It has to be thin enough to fabricate and not bulge the exchanger.

I want to paint the exchangers (I think) rather than have a ceramic coating. I'm not certain yet, but I think I will just use high heat primer & paint and try to cure it in the oven (my wife is understanding).

More to come...

These are the pics just after I got the shells apart and BEFORE the parts cleaner:

_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[pioneer1]

If you wash the insides be sure to bake them well. Once in use that residue sure stinks as you drive o
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"Always waiting for tomorrow ruined everything"

'85 Porsche 911 Targa

'76 Westfalia project

[rastomas]

There should be NO carbon deposits like that on the tin part. The only part that should have carbon on it is the interior of the exchanger pipe itself.
Make sure it's oiled up dirt, and not carbon.
I didn't dis mine, just had them baked first, then painted and baked again.
Pie-plate type aluminum will NOT work in that enviro. It will disintegrate quickly.
File the ports flat before you mount them. All four.
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"It's not 'You are what you eat', it's 'You are what you don't SHIT". Wavy Gravy.


'74 Westy

[ivwshane]

I used the same heart shield product as the one you are looking at but I think this product is actually closer to what the original was:

https://www.amazon.com/gp/aw/d/B003RBC1AG?psc=1&ref=ppx_pop_mob_b_asin_image

There are two main differences to think about:
Your link is thicker than the original and the one I posted is of a similar thickness. The thicker material may impede air flow but I haven’t been able to test this yet.

Your link has a similar gauge metal backing and may hold up better than the one I posted which has more of a foil backing rather than a thin layer of aluminum.

Another option for your tins that you may want to look into is to powder coat the tins with a high temp powder coat.
For the actual heat pipe I powder coated only the pipe and flanges and left the heatsink bare metal (it’s aluminum so it won’t rust unlike the rest of the heat pipe).
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[Ludwig van]

The black deposits inside your exchangers could indicate exhaust leakage. Years ago, I took my exchangers apart to clean them, due to nasty smells. The PO had a leaky oil cooler that let oil get into one of the exchangers. While I had the shells off, I decided to check for leakage. I got 2 cheap foam rubber balls and drilled a small passage (maybe 1/4") through one. I put soap solution on the finned part, blocked one end of the exchanger with the solid ball and held the drilled ball on the other end with the blow gun from my compressor going through the hole. When I blew air into one of the exchangers, I saw bubbles. Long story short, the pipe inside the finned piece was cracked and there was a void in the aluminum casting. Attempts to weld the pipe didn't go well, so I just stopped using the heat - we don't drive the Westy in winter anyway. You might want to check for leaks before going any further with this job.
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Our iPad e-book "Camping With Ludwig Van"
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[BusBerd]

[ivwshane]

While it may seem to make more sense by having the metal side against the heat pipe but my tests showed that the metal doesn’t stand up to the heat like the fiber does. It also didn’t deflect as much heat when having it that way vs the heat pipe contacting the fiber side.
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[BusBerd]

[ivwshane]

I don’t think the breaking down of the metal facing from heat will be an issue as I used a heat source that is way above the backing’s rating. What I gained from my informal experiment was that the heat was better deflected (meaning the outside of the heat exchanger was cooler) with the foil facing out.

However there was one more benefit to having the foil facing out that I forgot about. As you may have noticed, your heat exchanger was soaked in oil and I figured oil soaking would be minimized and maybe even burn off if it fell on the foil instead of getting soaked in the fibers.

That being said, it’s why I believe the other heat shield I posted would be a better match, not only is it thin like the original but it’s composed of a basket weave type fiber which may not soak up as much oil.
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[SGKent]

Just as an FYI from older threads here on TheSamba. If the air flow thru the heater boxes is blocked the aluminum fins will melt. That means they are getting a lot hotter than 700F. They always have air flowing thru them, whether it is dumping or being used in the cabin that cools them down. The late system that Richard Atwell took readings from is covered in a metal plating on both the U tubes and F pipes. Inside is the same material like you found in the heat shields. Exterior temps will read lower than what the inside is experiencing. Aluminum melts at 1220 F so if the heat exchangers melt aluminum fins with the air cut off they are getting to at least 1220 F.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[ivwshane]

I was using map gas as my heat source...:p

But you do raise a good point. If the air is restricted a little, is it enough to melt the aluminum? I hope I don’t find out the hard way.
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[BusBerd]

[ivwshane]

The one I posted does not have a rigid backing but instead is backed by foil. I don’t think sagging will be an issue nor will you need any adhesive to keep it in place.

A rigid metal back using the mesh fiber of the one I linked to would be ideal but I’ve never seen anything like it.
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[BusBerd]

I have finished sandblasting the rest of the shell of each of the exchangers. I painted them as well with high heat paint.

I returned the thicker insulate and purchased the thinner one that was suggested above. (Pic below)

Now I am turning my efforts to cleaning the actual exchanger. I would like to sandblast the exchanger. I read on samba on one of the threads that it is suggested to plug the ports of the exchanger before sandblasting and I am wondering why. If media gets inside the exchanger can it not just be blown out? I want to clean out as much of the carbon deposits as possible on the inside of the exchanger. I soaked them in the parts washer overnight, but noticed very little difference. What is the best way to clean out the inside of the exchanger? (I do plan to Dremel the the edges of the muffler/exchanger ports, but that will only reach a little way inside.)

Thank you for your help!

_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[ivwshane]

My heat exchangers are the later style and I didn’t blast the inside because it was super rough unlike my other exhaust pipes so I couldn’t be sure I was going to be able to remove all the media.

Looking good so far though!
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77 westy 2.0 FI
69 ghia coup 1600dp
70 single cab

[BusBerd]

[SGKent]

[airschooled]

I avoid blasting the insides of exhaust pipes anywhere near the exhaust ports. "Reversion" is the tiny bit of exhaust that is sucked into the combustion chamber with every intake stroke. Because the valves aren't magical devices that open and close instantly, there is always a TINY bit of overlap between strokes on a 4-stroke engine. (This is also why copper exhaust ring leaks can be a tiny vacuum leak source.) I do not like blast media in my combustion chambers, so I don't blast the insides of any exhaust components that attach to the head. Muffler? Sure, but no go on the inside of the header pipes for my engines.

I suspect a long freeway drive on a well-tuned engine should burn out any meaningful carbon deposits from those pipes.
Robbie
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[SGKent]

just as an FYI, blast media, expecially minerals like glass or garnet etc, create a static charge that holds some of the material to the metal. The only way to get all of it out is to use a mixture of water and wetting agent that nullifies the charges and washes away the particles. That is why machine shops wash the things they glass bead. Then immediately hit it with clean dry air to blast anything else out and dry the metal to stop flash rust. Any media that gets into the outer shell will end up inside the bus eventually. Media on the inside of the pipes can be washed out with the soapy water under pressure, then air as I mentioned.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[BusBerd]