First of all, I discovered that when I puked coolant all over the floor this week, a good deal of the hot coolant got all over my Hayden fan controller and fried it. The fan will no longer activate. I am waiting on a thermal switch so I can get my fan working again.
I went ahead and tried running the car again anyway, this time with the cap on. Once it reached operating temp, I noticed coolant was trickling from where the cap seals to the radiator. Now either there is just too much pressure in the system or the cap is just old. It is an oem cap, so just for insurance, I bought a new cap which had a lot more resistance when placing it on the radiator. It should offer a better seal.
I also pulled out the thermostat and discovered that it was a stock 192* Motorcraft stat. I totally thought I did a 180 when I first got the car. Must have confused it with my '87. It had a small bleed hole at 12 oclock from the factory.
I bought a new 180* stat from Autozone. I put both stats in a pot with water and placed them on the kitchen stove with a thermometer, as MFE described. Sure enough, the 180 opened at 180 and the 192 opened around 192. Although the autozone 180 opened quite a bit more than the 192 when both were fully open. I drilled a 1/8" hole at 12 oclock in the new 180 stat.
I then went to the yard and got a new thermostat housing. I will drill and tap it and use a thermal switch with 75 amp relay to activate the fan. Going to the vw dealership to pick up the switch I need this week. I did some research and found that an 83 rabbit 1.8L has the switch I need in the correct operating range. No more cheap controllers. The Hayden is a huge pos.
Hopefully everthing will be fine.
Meanwhile, I also went ahead and pulled the plugs just to see if I could see one of the different from all the others. They all looked consistent. I have also detected zero white smoke, no oil in water, no water in oil, and not exhaust smell in the radiator. So it does not look like a HG.
I should have it all assembled this week when my fan switch is here. I will post the results as I get them.