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Ugh.... here goes.... (ready for the eye rolls and laughing out loud). When cutting into the coolant lines for the isotemp water heater, which engine coolant line is which? Is the one with the air bleeder valve the one that goes TO the water heater? Or is it the other way around? :unsure:
 

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I cut into both of them and essentially connected the isotemp in 'parallel' with the cab heater. That way the isotemp doesn't affect the cab heater output.
 

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But ideally you want the heater core input to go to the isotemp first. More important in the winter.
 

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But ideally you want the heater core input to go to the isotemp first. More important in the winter.
If the heater core and isotemp are connected in parallel hot coolant from the engine goes through both units at the same time. They both get the same temperature engine coolant.
 

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If the heater core and isotemp are connected in parallel hot coolant from the engine goes through both units at the same time. They both get the same temperature engine coolant.
Unless the heater core is pulling the heat out first.
 

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Another quick question. All went well until.... I got the engine up to temp and both of the threaded connections are leaking at the water heater. I used Loctite 592 per the instructions on the water heater. Has anyone else had this problem? Any ideas as to another product? Would white plumbers tape (teflon) just melt? Help!!! I am flailing right now!
 

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I believe so?
EDGE INDUSTRIAL 5/8" Hose ID to 1/2" Female NPT FNPT Straight Brass Fitting Fuel / AIR / Water / Oil / Gas / WOG

I am wondering if I am supposed to totally glop the thread sealant on the entire fitting? I didn't apply liberally as I had recently watched a video from loctite describing the need for very little product on threads?

Thoughts? Go again with a ton of 592 all over threads or go with teflon?
 

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Regular ol' pipe dope would work.
It's usually rated for well below freezing, up to about 400*F and somewhere around 200 psi.
It usually seals before it sets and most of the new ones stay pliable, but I would wait until it sets up for at least a few hours before adding heat and pressure.
You likely didn't add enough sealant, didn't tighten them enough (tapered thread?), Didn't let it set up long enough or all of the above.
 

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Agreed on all of the above. Such a bummer as the heater is in a very tight spot to be reworking the fittings. Ugh. I am planning on reapplying the 592 (covering all of the threads), tightening the fittings a little more, and letting it set up for at least 24 hours. I am definitely happy that I put ball valves at the engine end of the lines! (Kind of wish that I had put valves at the heater too) Thanks for responding everyone. It really helps when you are fumbling around on your own to know that there is a great team out there that has your back!
 

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Is that how that loctite stuff dispenses? Like thread lock?
I've never used it.
I would have used regular pipe dope.
The thick, pastey stuff that you brush on. They have newer stuff that works on all materials and has a wide temp and pressure range. And it's like $5.
Pro dope
 

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592 comes in a squeeze tube and is a bit running. I've got a persistent coolant smell in the van when we start up, so I think I have a tiny leak. I may redo with Pro Dope and see what happens.
 

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Probably a silly question, but my neighbor who is a retired pipe fitter said to just use teflon tape. He says the temp range is more than enough for the heater???? Has anyone just tried teflon?

Temperature Range: -450°F to +500°F (-268°C to +260°C) PTFE is completely stable up to +500o F or +260°C. Decomposition is slow up to 750°F or 400°C. Although decomposition will occur on contact with naked flames. Use 3/4" (19mm) wide tape for fittings up to 2" (51mm) in diameter
 

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I've been around the trades for 30 yrs and it's another one of those debate topics. Everyone has their own method that they swear by and say they never have issues with. Some plumbers only use tape, some only use dope, some use both.
I tend to use the tape on tight plastic threads and use the dope when dealing with metal on metal. Especially when it's a gas line.
I like the tape for plastic fittings because they tend to stick a bit more (plastic on plastic) and be a tighter fit The Teflon helps with friction and has less space to seal. The dope is thicker and I prefer to use is on black pipe with tapered threads as it really fills the gaps and makes a good seal. I've never had a leak with the dope.
Just make sure your threads are clean and undamaged.
I'd say the tape or the dope will be ok in this application as you are not dealing with high heat or pressure.
Or gas for that matter. The tape might be a little more convenient as you don't have to give it a while to set up. If you don't mind waiting over night for the dope to set up, I personally would choose the dope just because I've always used it on all metal threaded fittings for both water and gas and never had a failure.
 

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I ended up talking to tech support for isotemp and loctite! Even though the instructions on the Loctite 592 state that you don't need to cover all of the threads, both of the tech support guys recommended good thread coverage. So I lathered the 592 on the threads in excess and am going to let it "cure" for 72 hours before I even start the engine! I am hoping that this works and will keep everyone posted! Fingers crossed! ?
 
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