Cadillac Owners Forum banner
1 - 8 of 8 Posts

· Registered
192 Posts
Discussion Starter · #1 ·
Well I was doing some winter prep on the car today.

So I pulled the thermostat out and poured in a 3 crushed cooling system tabs. I put the thermostat back in and topped up the cooling system.

I took the car for a drive and had the scanner in my hand while I drove. Temp started going up, and up 190, 195, 200, 215, 220, 225, 230, at that point I knew something was wrong, so I quickly found a parking lot and pulled in.

By the time I got it shut down the temp had hit 260F.

Coolant was shooting out the top of the res. UGH.

Well I popped open the rear deck and checked the motor out. (this is a Fiero)

Engine cap was hot, but rad cap was cold. After letting it cool all the way down, I popped the thermostat out, I found the powder had plugged the thermostat solid. CRAP CRAP CRAP CRAP.

Well I had blown over a gallon of coolant out onto the ground but I sealed everything back up and fired it up. Temp went through the roof. I shut it back down and let it cool again. I fired it up and headed right for a gas station a block away. I parked it till it cooled to 180f and slowly added water to the engine filler.

After burping the system a dozen times, (its a Fiero rad in front of car, engine in da back makes for interesting air pockets.)
I finally got the air out of the system and drove it home.

It seemed to run alright, but that stint up to 260 has me worried.

Now the huge question that remains is how in the heck did the powder manage to clog the thermostat the way it did. Now I am worried about putting the power back in the car and having it all happen again.

· Registered
01 frontier , 89 Shelby CSX vnt
14,682 Posts
Capt Fiero said:
3 were added for a total of 6 over the past 6 months. This is an oversized cooling system, I think from dry it is 6 gallons.
wonder if something changed with how the system flows now that its being fed coolant from the nose of the car to its zip code in the trunk ...for us when we add too much 4.x curry we would clog the heater core your case the heater core is futher away , if you retained it ....if memeory serves our heater cores are being fed coolant at all times regardless of what our desired temp is ...they alomst act like a second radiator ....

just wondering , makeing theroys

· Registered
192 Posts
Discussion Starter · #6 ·
Do you notice the little loop on my thermostat.

Well I set the up the Caddy to use the same quick change thermostat as the Fiero. We have 2 coolant caps. The one on the rad that we almost never remove, and the coolant fill cap that is on top of the motor. We just remove the coolant cap on the motor pop out the thermostat and fill it up. Then replace the thermostat and cap and are good to go. The reason for this is that our rad sits so low in the front of the car that there would be almost no way to fill the system as the motor is higher than the rad.

I have included a pic during the build process. I circled the housing for the thermostat.

I put the power in there, let it sink into the coolant for a bit then replaced the thermostat and went for a drive.

The quick change is nice so that we can swap to a high temp, low temp or no thermostat for track times. It is factory on all the Fiero's and has the same bolt locations as the Caddy 4.9.

Our heaters are the same as yours, they always have flow.

I have since replaced the thermostat and topped up the system and everything seems to be fine.

What is the normal operating temp for the 4.9 when installed in the caddy.

I have been running with a low temp 180' thermostat but just recently changed to a 195 for the winter. It runs about 200f now. But does get as high as 225' before the fan has a chance to drop the temp back down. ( Fan kicks in at 220 and shuts off at 201.)

1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.