As I mentioned in my last post, I have been having engine coolant temperature issues. Low speed running and traffic saw temps as high as the low 100's (Celsius) and on one run into the city for work, I saw 110 before the fan kicked in.
I had added a blanking cap to the radiator filler in order to pressurise the expansion tank. This only served to blow out the overflow spigot on the neck as it wasn't designed for pressure. This left me with a choice: either change the filler neck, or change the expansion/overflow. It will sound silly but I opted for the latter. The benefits were that it simplified the plumbing, and then I ran a simple overflow recovery tank. When the water heats up its purged to the overflow tank, and when the system cools down it draws liquid back into itself.
A couple of test runs and it seemed OK, then I had one run where it would not drop below 98....and the radiator and pump inlet were cold. This means the thermostat wasn't opening, so potentially a big airlock.
In order to get a better understanding of the true temperatures, I purchased a bluetooth ODB-II adapter which plugs into the ODB-II adapter on the loom, and allows me to query the ECU with an app on the phone. I jacked the car up as high as I could at one end to elevate the filler, and then ran the engine for 15 mins with the cap off. At exactly 15 mins and 98 degrees...a huge surge of air bubbles came up out of the filler. I then switched on the fan and was able to cool it and see the thermostat open and close. I let it cool down and then refilled and seal it in the morning. After another 6 decent length runs I am now seeing temps consistently down between 88-91 degrees, and it rises to 95 while stopped in traffic with the fan going. Best of all the phone app is giving me the temperature directly out of the head rather than a sensor I fitted in the outflow (which I still need to move). Problem solved and its much cooler under bonnet, and in the car, as well as being tidier (and not leaking).
The one other thing the ODB-II app has shown me is that intake air temperatures are running quite high....so that will be the next project.
