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Old 12-25-2012, 05:22 PM   #1
Senior Member
Join Date: Sep 2009
Posts: 402
Remove Hydro Hot

I know not all Alpine’s are built the same or may have different model Hydrohot. I had a coolant leak around the outside of my exhaust that got worse to the point, I could no longer use it. There is no access hole in bottom to get to it. The sheet metal base of the Hydro hot is ¾” away from the holding tank bracket. There are 2 ¼”bolts in the front back that hold it to the floor through 2 pieces of angle iron. The front bolts are unbolted easily. Since you can’t to the top of the rear bolts, you have to use a chisel to break them off. When I put it back together I used super glue on the heads of the rear bolts to the sheetmetal. The rear 2” angle is bolted on the back and welded on the front to another angle iron. I had to use sawzall to cut off and then made bracket to bolt both ends back in. (See Pictures). Probably the hardest part is cutting a hole in the sheet metal floor, without cutting hoses, wires or pipes. I used a jig saw with very short metal blade and cut out pieces until I could see in there. I started at the weep hole and started cutting to the back first. You can cut under the holding tank to make the hole a little wider. Cut about a 4X15 hole. Made aluminum sheet metal cover. I left 2” on each end of the Hydohot so I had metal left to bolt it back in to the angle iron.
You have to drain the coolant from the front drain valve. So you don’t lose all the engine coolant, you have use pinch of pliers on the two hoses going to the engine. On the hot and cold water pipes, I used ½” pipe caps, otherwise they drip forever. Since there is no way to disconnect the exhaust pipe at the heater, I used a sawzall to cut the pipe and used 2” stainless steel band clamp to put it together. The pipe just threads into the bottom of the heater with a pipe flange. I used antisieze when I put back together.
Turn off ac and dc power. On the front side remove the circuit board, the front cover. Disconnect the diesel lines and cap or blow back with a air hose, or they will siphon back. Disconnect the a/c from the junction box. Disconnect the two 3/4” red coolant line on the front. The back two coolant lines are behind the Hyrohot and you cannot swing 1 1/8” wrench to loosen them against the holding tank. You have to partially slide the tank out to loosen them. You have to use a pinch bar to raise the tank up enough to clear the exhaust flange to slide it forward. By using wood block to hold it up, it will barely make it through the access door.
Once I had it out, to find my leak, I talked to Roger Berke on the RVhydronicheaterrpair.com forum. He said to do whatever it takes to fix it, since if send it back to the factory, they don’t fix it, they rebuild it. Rebuilt cost is $5500 or a new one is $6500.He told to plug the 2 inlets and 2 outlets with pipe plugs and caps. Put the radiator cap on and put air pressure to the overflow fitting on the neck. On backside through the insulation there was brass fitting that was cracked. There was no way to see or fix it while it was in the coach. After I fixed the fitting, it held air pressure in the system over night. Roger told me to do away with those ¾ “ air hose and fittings, cut them off and use ¾” inch heater hose to put it together using barb fittings on the tank and sling over the heater hose. He recommends using constant tension clamps on the heater hose. For the back ¾ hoses leave a loop on top of the tank , so it is easier to get back together. I also left a loop on top for the engine heater hoses. To get it back in I put some sheet metal pieces on the floor, so the back of the hydrohot metal would ‘t dig in. Hopefully the pictures help describe it. Also Roger said you don’t need the rubber boot for the intake air.

The pictures are not in any order.
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2007 Apex MDTS (425 hp) #75723
2007 Toyota 4-Runner
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Old 12-25-2012, 06:55 PM   #2
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Join Date: Jan 2004
Location: Summer Rowlett TX (Why?)/Winter Palm Springs CA Two Springs RV Resort http://www.twospringsrv.com/
Posts: 517
I love the way WRV installed the Hydrohot on the chassis and then built the coach around it with no thought of how to access a fitting leak in the back of it such as I had while sitting in an RV park in Texas 2 1/2 years ago. So, I cut a hole and installed a cover plate similar to what you did. Not limited to Apex. The picture of the back of the HH came from a coach in the body shop in Junction City with the holding tanks removed.
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Basil & Sue Shannon
Former Apex owner (Gary & Renee have it now)
Was Traveling Circus (2 clowns/Sage the Wonder Dog) Tent rotted. Circus folded.
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