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49 – Oil Cooler & Fuel Flow Sensor

I’ve had a few more days with the fuselage at home in the workshop, prior to its move to the hangar in preparation for painting.

Lots still to do, so I pressed on with fitting the oil cooler and fuel flow sensor.

Oil Cooler


This was the first time I’ve dealt with an oil cooler, so my first thought was “which is the inlet and outlet?”

On inspection, and after spotting the following by Vans in the manual, it was obvious that it didn’t matter …

The ‘top’ side is defined by the fluid fitting orientation since the oil cooler is symmetrical.

There are 45º and 90º fluid fittings … so you know what that means … CLOCKING!

I ended up having to screw one in and out a few times to stand a chance of getting the clocking correct.


Two P Seals are bonded to the cooler using silicone, not RTV.


Two beads of RTV are applied to the base of the Cooler Inlet Assembly where it contacts the oil cooler’s mounting plates.

It’s also applied to the corners to seal any gaps.

The little job of attaching the Inlet Assembly proved a bit more demanding than I anticipated!


The challenge was keeping the Inlet Assembly in position, locating the long bolts through the spacers, and nipping up the nuts all at the same time.

Consider locating the four FF-00077 Oil Cooler Spacers into position prior to placing the Inlet assembly with the RTV.

Pre-positioned spacers would have made the job of inserting the bolts much easier.

A helping hand is required unless you have very long arms : )


This is a view from below showing the underside of the Oil Cooler.

NB the Scat Tube routing is NOT the same as the manual specification, since I have fitted a Vetterman Trombone Exhaust.

Fuel Flow Sensor


Vans suggest you fit the Fuel Flow Sensor, a FT-60 Flow Transducer (Red Cube), onto the engine air inlet tubes using a mounting plate and high temperature cushion clamps.

This obviously works, but I found it really difficult to get a pleasing attachment orientation.

The EXP119 has some tempting spare location holes on the oil sump just above where the sensor needs to be located. I’d seen a picture in the Aircraft Speciality hose instructions of a suggested alternative, so I decided to try it.

I made a suitable bracket for the Red Cube to sit on … I used 2024-T3 1/8″ Aluminium Angle, hoping the “smooth” corner will prevent stress cracking.


I used some spare baffle material to provide some sort of damping top and bottom, hoping it might replicate the cushion clamps.

The holes in the FT60 are larger than AN3 bolt diameter, so the rubber should allow some damping.

I’ve no idea if this will help or cause trouble, but thinking about the hoses and engine vibration, some sort of “give” might be prudent.

We’ll see.


More fluid fitting clocking needed!

Vans suggest a 45º clocking for the AN823-6D, but I found straight down was a better angle for my setup.

I nipped up all the hoses prior to installation, enabling better access. The hoses have a natural bend, so I was careful to nip them up with their orientation correct.


The bracket installed on the spare holes in the EXP119 oil sump …


… and with the Red Cube installed.

This installation method definitely improves the hose alignment etc, and looks neater.

Whether it will stand the engine vibration and not cause issues with the sensor, time will tell!

Having just inspected the installation at 90 hours I’m pleased to say it seems to be quite happy.

In addition fuel flow readings have been consistent and accurate.

28 June 2023

Here’s the hose routing from the outlet to the FM200.


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