1994 International 4700 Conversion Begins

Hello all,

After much consideration over the last two years, I too purchased an ambulance to convert into an RV. It's going to be a slow process and I will try to keep information coming on my findings and provide pictures to support those who would like to take on a project such as this in the future.

My thoughts on "why" an ambulance:

I went back and forth between a used/new RV with everything already in place (toilet, stove, etc.) box truck and bus. I knew I wanted diesel; of those mentioned above, they either have a gigantic price tag (diesel RV), excessive mileage and a lot of time/money to make useable (bus, box truck). I am not much into toys; such as, Razor's, quads and the like so I had no need for the open space a bus or box truck offers. I am more of an everything needs a place type guy, so I needed storage. Ambulances come with a lot of storage which saves a lot of time and money.

Like most folks, I found "affordable" RV's to be rather cheaply made and very few diesel options unless your spending serious money. My "affordable" was less that 13K to start. RV's tend to have a lot of space which is awesome but can be rather limited on storage. I don't head to the woods with intention of spending a lot of time inside. I wanted a vehicle that would do many things and an ambulance fit the bill for us. Lots of storage both inside and out, somewhat well insulated from temperatures and built very solid.

That being said, I found this in Tucson 1436568353367.jpg
The wife and I drove down over a weekend and took it for a drive. Right away we knew it would work but it needed some TLC and in particular the brakes! How we made it home was a miracle. I did not find out just how much of a miracle until I took it to emissions and on the way back the brakes locked up tight and we were not moving! The right rear brake caliper was smoking hot and the brake pad was gone leaving metal on metal. It was like "welding" in motion! Anyhow, we managed to limp it home and the project truly began.
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The skinny:

1994 International 4700LP
5.9 diesel DT360A 23000 miles (on a rebuild I think)
Allison 545 automatic (rather slow going 4 speed)
Built-in 240 PTO driven generator (did not initially work)
4 wheel hydraulic disc brakes (nice but the rear is not fun/easy to work on)
Air parking brake (driveline brake)
Retractable 120V power cord reel (removed)

I am writing this first bit of information in retrospect, so please bear with me and my memory! Once home, we started cleaning it out.

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For the most part the truck was pretty clean, but I went over it with the vacuum and sanitized the entire thing. It must have gotten steamy/wet inside somehow and there was a bit of mold growth on the ceiling.

I tackled the right rear brake caliper and rotor first. I had to replace the brake rotor due heat damage from the locked up brake. Of course, since I had to go that far I changed bearings and seals as well. This was my first big project on the truck and not one I care to repeat! After I got the right rear rebuilt I gave it a run. It was still locking up, so I changed hoses. Still locking up, bought all new brakes, calipers and rebuild kits. Still locked up but this time it switched to the left side. Interesting....that told me it was not the caliper. I'd never dealt with a power steering pressure supplied hydraulic brakes before but I learned a lot! The brake calipers internally were in rough shape, with black gunk in them and torn boots they were in need of a rebuild. However, the power brake booster was apparently to blame for the brakes locking up. After a second very good flushing and cleaning of the brake reservoir, I changed out the booster and the brakes are functioning fine....for now.

This is where I will stop and mention: With whatever old vehicle you purchase just plan on changing fluids and filters right away. I checked everything originally and all the fluids seemed fine. It took me several months to find out that many of my problems were simply caused by old fluids and filters! It's not cheap on a vehicle this size but it has to be done. I tried to hold off a little until I knew the vehicle a little better, but it was a waste of time to have waited. I chased a few ghosts trying to figure out some problems. Notably; the transmission, the temperature was running a bit high (over 200) but it depends on where the temp sensor is and it was within maximum limits so I ran with it for a short while. The transmission started having a delay in reverse and that is what pushed me to change the filter as a test. A $12 filter and the transmission shifted instantly. That's when I wanted to kick my self for waiting. After changing all the fluids and filters the transmission shifts easier, smoother and runs cooler, the engine runs quieter. Everything about the drivetrain in the truck is better with new fluids. They really were not even dirty, just old. Lesson learned.... So, unless you are very sure the fluids and filters are new, just change them and spend more time chasing real opportunities for improvement!

I had cooling issues initially as well. The coolant was old and separated (change fluids!) when I pulled the lower radiator hose it looked like a bunch of melted cheese coming out! It took 3 flushes and two filters to get that straightened out. The radiator fan/clutch on mine is a thermal disc type clutch and was not working. Replacement clutches are in the $600+ range, so I decided to take a peak. Once I removed the thermal disc, I found the little piston "valve" that controls the clutch. The piston was hidden under some sort of dirt crusty stuff. I cleaned it off, checked that it would go in and out smoothly, placed the thermal disc back in and grabbed a hairdryer and a thermometer. I wanted to check to make sure the disc was functioning properly as well. Sure enough, the disc popped at the right temperature and I figured it was time to give it another shot in the truck. The fan clutch is now working just fine. It's amazing what a little crud will do to stop things from working properly!

I should also mention my background and tool requirements.

My early career started out as a equipment maintenance, machinist, welding, equipment design and manufacturing. I've been turning wrenches as a hobby for about 30 years. I'm not claiming to be great at any of it, it just helps get things done on my own and save money in the process. I had plenty of tools before I started this and now I have a lot more. The tools I've used for years, simply were not big enough for a vast majority of the truck. For example: the lug nuts are torqued to 450-500 ft lbs. If you're thinking about a project such as this; hopefully, you're thinking about these requirements. I had a fair idea as to what I needed. However, not being a heavy equipment mechanic, I underestimated the tool requirements.

Hopefully, that helps some folks understand what to expect.
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I took it up north for a camp out twice prior to some of the work mentioned and I have to say the 5.9L is fine but the Allison 545 is not a good match for the hills in AZ. Now, the fluids are all changed and everything is working much better, shifting easier, cooler, etc. I am looking forward to heading up the hill again but I am not expecting any miracles. I am sure many would agree the 545 is not a good match for large hills. Those of you that do not live near mountains may find the 545 acceptable but I would recommend something with more gears. Depending on what you end up with the 545 is a common transmission for this era medium duty truck as is the DT series motor. The DT466 would be nice but I really wish I had a 5 or 6 speed transmission.
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I am trying to keep as much of the interior intact, I don't plan on putting in a sink, toilet or stove at the moment. The door access from either inside or out on the passenger side makes an ambulance very versatile if it's part of the design. The access from inside and out changed how I wanted to use the truck on the first camping trip. RV manufacturers could learn a lot from that one feature alone!

This is the cabinet which is accessible from the outside. The lower double doors.


All my cooking gear is inside here. If the weather is bad, I don't need to open a single exterior door to make breakfast, lunch or dinner. Simply crack a window or two and get cooking!

As many have stated the wiring can be a nightmare. I was fortunate in that there was a pile of paperwork in the door to help deal with the electrical in the form of prints and drawings. The PTO for the generator did not work initially as I mentioned, blowing fuses left and right trying to get it to work. Turns out, someone who knew less than what was needed to play in the electrical was there before me! Many things were wired wrong and or cut. It may have been partly due to the legal requirements of the sale of an emergency vehicle. All the controls for the emergency lighting were pulled out. The control modules for the emergency lights are still in there but not connected and the switches at the front console are gone.

I've installed some additional 12v power supplies, and gotten the PTO driven generator to work after sorting out the wiring problems and now have 120v! Although, no one in camp is going to appreciate me running the truck to have the 120v. It's there if I need it, pretty cool. Take care before you cut any wires; at least in mine, they used many of the wires to complete either multiple functions or the same function from 2 or 3 different points on the vehicle. Cut a wire which appears to no be used and something that was working is no longer operational! A simple voltage meter will save you a lot of trouble. I picked up a tone generator at Harbor Freight, it's simple and easy to use. While not perfect, it can help you trace wires easily or through a thick wire loom! Remember the multiple function comment though, the wire you're trying to chase with a tone generator may be going to something you don't expect. Especially if it's a hot or ground; in my case, the hot and ground colors were every color imaginable and even some you can't!
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A very small part of the electrical headache/fun associated with an ambo purchase Message_1436716718390.jpg just keep smiling! You gotta remember, you're having fun!
In the process of figuring out problems I also needed an exhaust manifold. This was new to me as well. Not new to an exhaust manifold but the fact it came in three pieces! The center section the turbo was mounted on had a huge crack in it. This may have happened when I went camping in the snow but I am not sure. Once I got everything out I realized it had been repaired once before. Fortunately, international had the parts I needed brand new and in stock. Once I put it all back together I was hoping for a whole new experience in the form of power. Unfortunately, all I got was a much quieter engine. But hey, my engine did not grenade and it is much quieter!
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I removed the seat which was in the middle of the entry and pass through areas which can be seen in the previous pictures. As much as I hated to pull it out, it was always in the way. Four large bolts were all that was holding it in place. Now, what to do with it....I don't know. I've put in a new stereo in the dash and gotten the rear ambulance box speakers to work. I think the next thing is going to be installing an inverter. I've pulled the wires to supply the inverter but have yet to decide on the inverter size. I plan to power a tv, video source and video game system into the inverter. I also have 3 solar panels I will install to supplement battery power.
I will post more pictures as the work continues. Hopefully, my experience will add to everything already out there on these builds and save someone some time and effort. Best of luck to those ready to take the leap!
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Thanks, just got the Solar inverter installed last night. Now, I need to get the brackets made up to mount the panels and get the power ran.


I plan on attaching the panels to the drip rail for quick and easy storage/removal. Well, keep reading.....plans changed!
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Still playing around with the wiring, removed Whelen emergency light control boxes 20160314_162121.jpg . Pulled my Solar Panel wire and a 12v supply to previous emergency light. Figuring out how to use the existing light housing for the wiring. I plan on having a 12v supply and USB at the light just because I can! Too much fun with all the options one can come up with. This changed to with making the solar panels retractable.

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One thing that never seems to end on these rigs is the electrical and the tubing! It goes on and on! I have been pulling old stuff out and putting in new wires for the stereo, TV and sconce lighting for the side entry. The center raceway through the box is the main artery and is full of stuff. If you're planning on fishing wire, be sure to pull a few extra rope lines while you're pulling wires. You never know what you'll come up with and the extra lines to pull with are handy to have. Sure beats using a fish tape over and over. I've extended one of the power wires from a previous ceiling light that had a low and a high bulb controlled by a panel switch. I am going to use these wires to install the sconce light by the door and maybe install a relay so the side door light still comes on when the door is opened. Not sure, it's only 5 feet to the switch. Plan on using the existing exterior emergency lights in conjunction with motion sensors. If we walk up to any side of the truck the lights will come on. I also plan on putting in security cameras on all four sides of the truck and installing a monitor on the inside.

A bit of a pain in this tight space but I got the duplex outlet hole cut and got the romex pulled. TV, game system, dvd player etc. now have power. Well, they will as soon as I get the inverter installed.