Heater Hose Replacement Made Simple

I was Sleepless in Seattle worrying about replacing my 308's heater hoses. I was mindful they were over 25 years old and harder than a dead carp. I read other posts and they did not make me warm and fuzzy. As we are in the automotive service business I know hose and belt manufactures reccomend that hoses and belts be replaced in 18 month to 2 year intervals, and the 308 was long overdue. I had to previously removed the drivers side fuel tank to repair a leak, so with that tank out I decided to take the bull by the horns and replace the heater hoses. I have found a couple of tricks that will make the job easier, so with that in mind, here goes.

1st the drivers fuel tank is removed, with that in mind, you can see the heater hose and the brake booster line coming thru the rear bulkhead. They make a sharp bend upwards around a frame bracket. You need to remove the hose from where it connects to the cylinder block and then pull the heater hose straight thru the bulkhead so it runs parrollel to the door sill. The heater hose is the smoother of the 2. The braded hose is for the brake booster and should not need to be repalced. Next you need to open the drivers door and pull back the carpeting around the rear of the door sill ajacent to the serial number plate. You will see a formed aluminum plate pop rivited to the body. you need to snap the heads off the rivits and remove this plate as it coveres the access hole for the heater and booster hose. This is where these hoses bend thru the rear bulkhead and begin their run thru the door sill. Next remove the drivers seat 4 allen head cap screws 6mm cap size. I will explain why the seat should be removed a little later on.

Next go to the front wheel well and remove the inner wheel opening panel at the rear of the opening 5 phillips head machine screws. Carefully pry this panel out and down, its aluminum don't bend it. This will expose the hoses as they travel from the horizontal door sill up into the spare tire compartment. There is a metal band about 1/2 way up the hoses and you need to unbend this from around the hoses.

Open the hood and on the drivers side you will have to look between the defroster plastic bend and the aluminum pedal base and you will see the heater hose comming up from behind and connecting to the base of the "Y" fitting at the back side of the heater control valves. Soak this hose with spray penetrating oil be fore trying to remove the hose. The heater control valves are held to the bulkhead with 2 10mm nuts remove them and gently pull the assembly forward, this will allow better access to the hose being replaced. After the clamp is removed you can (after soak time) begain to move the hose around and break the hose loose. Once this hose is off the "Y" you can now move the heater vales off to the side out of the way.

The easiest way to replace this nearly 7 foot long hose is to connect a new hose to the end of the old one and pull the old hose out from the rear!!!!! Here is a trick that worked well for me. I purchased a double ended barbed brass hose fitting ( like you would repair a garden hose with). I sprayed the inside of the old dry hose with penetrate oil and pushed the barbed fitting into it. I then took the new hose and sprayed it too and pushed it onto the other end of the barbed fitting. With help at the front end of the car of a friend pushing the hose, I was at the rear wheel well pulling at the same time, the hose moved easily from front to back. We watched for the fitting to reach the access hole at the rear of the door opening. Once there I took a long punch and and hammer and bent the back edge of the access hole down to allow a more gentle bend for the hose as it passed through this area. I pulled the hose thru and had excess hose at both in the front and in the engine compartment.

Now at his point I decided to add a couple of parts that would solve a potential problem with the hoses along the road. I added a shut off valve at the cylinder block where the heater hose connects. A valve here allows me to turn the heater water off should the hose burst along the road. To me this is an addtional safety factor should a hose failure occur.

I had earlier decided that I wanted to replace all the heater hoses behind the dash and running to both heater cores. There is another long heater hose from the lower main aluminum water pipe up and "Teeing" behind the power brake booster. Its damn near impossible to see and no way in hell are you able to remove the clamps. At this point it was bier time, cold cold bier. after much bier consumed and lots of head scratching I formed a plan. If I could get some extra room behind the power unit I might be able to actually see the end of the hose and get to the clamps.

I decided to remove the booster unit and master cylinder but I could not get to all the bolts so that was out. I then figured that if removed the bolts that hold the aluminum pedal base and then the booster hose maybe i could get enough room to get my hand behind and remove the clamps. There are 2 17 mm bolts on the spare tire side of the pedal base and then(remember why we removed the seat) under the dash there are 2 13mm bolts. While I was there I removed the clevis pin for the clutch cable. I was laying on my back under the dash with my feet over the targa bar, an interesting position. One of my managers saw me and told one of the techs that I looked like Mork from Mork and Mindy.

I was able to move the booster away from the bulkhead and off to the right hand side of the car, allowing the much needed access to the hose and the "T". Now this main hose that comes from the lower aluminum radiator pipe up to the "T" and then 2 smaller hoses, one of these hoses go to the left heater core and the other goes to the right side heater core. I removed the hoses from both heater cores and on the rhs hose I installed my hose barb and pushed on a length of hose for that heater core. This hose also runs behind the booster so I had the hose longer to pull thru and then pull it all back in place when I installed the long hose from the aluminum radiator pipe. It is much easier to acces the hose for the drivers side heater core. With the hoses , "T", and clamps in place I pulled all the hoses back in place and then cut the excess off and reconnected the hoses to the heater cores. Before I reinstalled the heater cores I backflushed both and removed a lot of sediment. On the large hose, I also added a shut off valve, so I can shut off the heater water supply at the pressure and return sides. I replaced the short hoses on the heater control valves as well. All heater hoses have now been replaced as well as all new stainless clamps. I used vasoline on the inside of the hoses so they won't sieze on the nipples.

I used NAPA black 1/2" hose for the run from the motor to the heater control valve. I used 5/8" black NAPA heater hose for the long run in the spare tire well. The reason I used 1/2" thru the body was to get a little more clearance. It will expand enough to fit the nipples without a problem. Be sure and use the black hose it is much more flexible and slippery. I did not use any silicone because this car is going in for a bare metal respray next week and I did not want silicone on or around the body. That my story, and I'm sticking to it!!!!! I forgot to mention that I had also removed the spare tire well insert. This makes the hose replacement much easier. Any questions or thoughts just pm me.

Howard Musolf
1981 308gtsi
Maserati Spyder
2 many brass era cars

 

I did add valves at both the engine/pressure side of the system and at the return side of the system. The second valve was placed by the heater control valve. I can shut off all water flow through the heater system. If I should have a hose failure I can isolate and shut off all coolant throught the heating system and not loose critical coolant for the motor.

Howard Musolf
1981 Ferrari 308 gtsi
Maserati Spyder