Thermostat doesn't open after new radiator hoses

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I just put all new radiator hoses on my Spider and a new overflow bottle. My new thermostat (from Vicks last summer) which has previously given me no problems seems to not be opening. The reason I believe this is the the fan doesn’t turn on and the engine overheats pretty quickly. I forced the fan to blow and then noticed the lower radiator and hose are cold...this happened after running the fan but I still think it's the issue.

I re-drained coolant and re-filled today with the front elevated, then part way through lowered the car flat and did the second half according to Ernest Build’s method, filling up the rear coolant hose above the head, which succeeded last time. But with no improvement. I guess there may be an air bubble still stuck under my thermostat…blindly guessing this detail since I’ve read something about it.

The only differences I made to the system when I reinstalled are: I coated the thermostat with simichrome polish on the outside to shine it up and a lick of vaseline at the hose attachments for easier removal next time. I've read simichrome is heat resistant but the heat is coming from the inside so I don't see this as a risk.

I left the hose coils inside the new hoses, which the previous owner had installed for stiffness. I think I solved his problem since I too was having hoses collapse...I discovered the narrow hose from radiator cap to overflow bottle was undersized. If I removed these hose coils it would be a lot easier to massage the air out of the hoses.

Hoping this is a common issue.

[18Fiatsandcounting]

Hoping this is a common issue.

Overheating is definitely a common issue, especially on the 2L engines. In your case, it sounds like the thermostat is not opening, and there are three common causes, with #1 being most common:

1. The thermostat is installed in the wrong direction, that is with the ports going to the wrong hoses. Easier to do than you might think. With the thermostat out of the car and cold, the port that is closed (that you can't blow through) must be connected to the lower radiator hose. If that one is lined up, the other two ports fall into place in terms of where they go.

2. An air pocket in the thermostat housing. You would think the air pocket would eventually rise to the top, but sometimes it doesn't. Try tapping on the thermostat with a rubber mallet. You can also loosen the connection for the lower hose to the thermostat until fluid comes out, and sometimes that will flush out an air pocket as well. The 2L engine seems more susceptible to air pockets due to the fact that the engine sits higher (relative to the radiator fill cap) than the smaller engines.

3. Bad thermostat, like it got stuck in the closed position. It does happen.

-Bryan

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You were absolutely correct. I redid everything and drilled a hole in the thermostat valve, it now works properly. Thanks!