Mounting Of Coolant Radiator Completed

Yesterday’s work session, although short, completed the installation of the coolant radiator. The two inboard bolts that secure the radiator to the FF-1204A cooler box frame received washers as necessary to fill any gaps between the radiator and the cooler box frame. With the spacing shims still in place, all the bolts were torqued to specifications while verifying that the shims still remained loose prior to removing them.


The next step involved the use of high temperature silicone again. The FF-1209 seal face is a frame that slips over the front of the radiator. The face of this frame will provide a flat surface for a thick soft gasket that will make an air seal between the cooling duct in the lower cowling (yet to be installed) and the face of the radiator. The FF-1209 seal face is slipped over the radiator and the builder is to make note where its placement is across the upper and lower tanks on the radiator so a 1/8" bed of silicone can be placed under those areas to bond the seal face to the coolant radiator. I took this one step further and placed tape above and below this area and also on the frame … so after the silicone is applied, cleanup of excess silicone material will be easy without leaving messy streaks on the paint or the radiator.

Radiator masked off along with the FF-1209 seal face. The horizontal black band between the tape lines on the radiator’s upper and lower water tanks is where the beads of silicone will be applied.

Applying a 1/8" bead of high temperature silicone to the upper tank.

Once the silicone is applied to the radiator’s upper and lower tanks, the FF-1209 face seal is slipped onto the radiator, pressed flat against the upper and lower tanks and taped in place while the silicone sets. The plans also call for placing beads of silicone on each side of the radiator between the radiator and the FF-1209 face seal.

Two additional vertical beads of silicone are laid down where the FF-1209 face seal meets the radiator on either side.

The next step in the plans involves installing the coolant hoses, but I did not want to possibly disturb the curing silicone, so decided to prep and paint a couple of small parts and will finish up plumbing the radiator during the next work session.

Success! Cooler Door Seal Completed & Radiator Mounted

Yesterday, before digging into the cooler door, I wanted to finish up on the oil tank vent tubing by making a joggle to move the tubing away from the stiffener (the previous post has a photo of how close the tubing is to the stiffener). To do so I used a heat gun and gingerly warmed the tubing up enough that a joggle could be carefully formed … thus moving the tubing away from the stiffener.

Oil tank vent tubing after using a heat gun to soften the tubing up a little so a joggle could be formed. Gloves were worn while holding the warm tubing in the desired shape as it cooled. Once cooled, the tubing took the desired set.


I waited until early evening to attempt opening the cooler door (this gave the silicone a full 24 hours + to set) and happy to report it popped right open. I was planning on peeling the packaging tape off the fuselage to lift the door and packaging tape as one, but as soon as I began applying pressure to lift the tape where the edge of the door was … the door just popped open. There was one area along the top of the door where the silicone was not quite fully cured and a little pulled away from the door. But inspecting the door reveled there is a good seal above and below the spot that pulled away … so time to move on.

The cooler door with its newly formed high temperature silicone gasket.

Placing the clear packaging tape down over the entire firewall area first and then slathering it with Vaseline worked great! I would whole heartily recommend this method to anybody faced with this task. May also be best to let the silicone cure for another full day prior to moving the door but admittedly, I was getting impatient and wanted to move on.


With the cooler door fiasco in the rear view mirror, continued on to the next step … fitting the coolant radiator. The instructions point out a tight fit is desired between the radiator and the two FF-1204B&C upper and lower ribs that make up the cooler box. The builder is to strive for 1/32"of clearance between the edges upper and lower ribs all the way across the core of the radiator. There are two things going on here … first the clearance measurement, plus the goal is to position the radiator so the radiator is parallel with the edges of the FF-1204B&C cooler box ribs. The plans suggest elongating the mounting holes on the radiator (if necessary) to achieve the clearance and positioning of the radiator. By now, I have learned if Van’s plans say “it may be necessary” to perform a task … it will be.

Initial test fitting of the radiator. This reveled the holes do indeed needed to be elongated to move the radiator inboard a little so it will be parallel with the upper and lower cooler ribs.

Using the Dremel tool outfitted with a cutter bit to elongate the three mounting holes on the frame of the radiator so the radiator could be positioned parallel to the edges of the upper and lower cooler box ribs. Later, the two screw holes on the inboard side of the radiator needed to be elongated as well.


To make the task of measuring easier, I decided to rummage around in the scrap pile and found a couple of pieces of .032 aluminum and used them as 1/32" spacers for setting the clearances between the radiator and the FF-1204B&C cooler box ribs. After a couple of cycles of on and off and tweaking the holes with a rat tail file, the fit was finally acceptable and the three bolts that mount the frame of the radiator onto the firewall were tightened down. This was done while the .032 spacers were still in place between the radiator core and the edge of the upper and lower cooler box ribs to hold the positioning.

Looking closely at the photo, one can see the .032 aluminum spacer placed between the radiator core and the edge of the FF-1204B cooler box rib … there is also another spacer out of sight at the FF-1204C cooler box lower rib.


The radiator is now mounted, but the two inboard bolts will require washers added as spacers. This is because the radiator needed to be offset inboard, thus leaving a gap between the radiator and the cooler box frame. The gap came as no surprise because the instructions elude to the possibility of needing to add washers as necessary to fill the gap.

Coolant radiator mounted and snugged down at the firewall … the two inboard bolts will require washers added as spacers.


Did not have enough time to finish placing the washers on the remaining two mounting bolts, but will finish off that task first thing during the next work session at the hangar.

Cooler Box Door Act II & Mounting The Oil Tank

This afternoon went for the second attempt to make the cooler door gasket after the first attempt met with utter failure due to the use of Boelube as a release agent for the silicone. This time around I changed things up a little, in that packaging tape was placed on the firewall first then the tape was coated with Vaseline. The idea being … if the silicone still wants to stick to the tape, at least the cooler door can be removed from the firewall by peeling the tape away from the firewall without bending the door up. After roughing up the door again and cleaning with Acetone, a liberal coating of high temperature silicone was applied to the door and then the door was placed on the hinge, closed and pressed onto the firewall then taped closed.

Cooler door Act II - Coated with high temperature silicone and ready to be taped closed for the second (and hopefully successful) attempt to form a gasket.

Cooler door taped closed and will be left to percolate for a day or two.

Normally, the next step is to mount the coolant radiator and associated hoses … but need to wait for the silicone on the cooler door to cure first ... so moved on to mounting the oil tank.


The oil tank itself is a piece of cake to install … in that it just slips down into a cradle and is secured by two band straps. Prior to tightening down the straps, the ring band that seals the top of the oil tank onto the body needed to be unlatched and rotated so it is facing forward … it was right adjacent to the carburetor and would have been impossible to unlatch without removing the tank. Doing this should allow the top to be removed to clean the inside of the tank without removing the tank from the airplane … this is a necessary task if burning leaded fuels on a regular basis because over time the lead will form a nasty paste on the bottom of the tank. I was a little disappointed not to find a torque specification given for the strap hardware, so I winged it and made it tight, but not overly so.

Lowering the oil tank through the band straps.

Once the tank is in position and the bands have been tightened, the air vent pluming which consist of a short piece of rubber hose and a 28” piece of tubing is installed onto the vent pipe on the tank. To keep the tubing away from the air filter (not yet installed), a #19 hole needs to be drilled into the F-1201Q battery angle so the vent tube can be wire tied onto the angle preventing it from touching the air filter.

Drilling the #19 hole into the F-1201Q battery angle that will be used to secure the oil tank’s vent line. Looking closely at the photo one can see the vent tube with the black piece of hose on the end of it that is used as a coupler laying on the upper fuselage skin.


The vent tubing was temporarily installed on the tank and a piece of wire was used to hold it in position while an Adel clamp was installed onto the gascolator’s right mounting bolt to secure the tubing.

A piece of wire is used to hold the vent line in the approximate position while the lower Adel clamp is installed (see next photo) to support the tubing.


The right bolt that secures the gascolator to the firewall was removed and an Adel clamp installed under the bolt to secure the oil vent line. Ran into a little issue here, in that, when the Adel clamp was positioned as shown on the drawing it was physically impossible to get a wrench on the bolt. The drawing in the instructions shows the clamp installed with the loop of the Adel clamp forward. I initially attempted to install the clamp this way … but found there were no tools in the arsenal that could be used to tighten the bolt because the Adel clamp blocked access to the bolt. To remedy the problem, the Adel clamp was flipped around so a wrench could be used to retighten the gascolator bolt.

The drawing shows mounting the Adel clamp opposite from this … but the clamp itself prevented getting wrenches onto the bolt, so it was flipped around.


Later, I’ll use a heat gun to soften the tubing a little so a joggle can be formed to direct the tubing towards the black hose that can be seen in the previous photo then securing it to the hose with wire ties. This will pull the tubing away from the stiffener on the firewall and also away from the edge of the fuselage out of view in the above photo.


Note: The hose clamps for the vent line hose and tubing at the oil tank were not installed at this time because the vent line will need to be removed later when performing the purging of the oil system … so there is no point in placing clamps on the hose and tubing knowing they will need to be removed for the purge. The purge requires placing an air source onto the vent fitting at the oil tank and pressurizing the oil tank to between 7 &14 psi (if memory serves me correctly) to force oil through the engine while performing the purging process which is necessary to remove all the air from the oil lines and oil passages inside the engine prior to initial starting of the engine.