Thermostat Replaced...Now what?

[wubie317]

A while back, I replaced the coolant (brown and worthless) and added a filler T. Initially, the car ran much cooler especially at freeway speeds. After a few weeks, I felt like something wasn't right. When started from cold, it would climb very quickly to operating temp and stay there. Especially going from start to rush hour traffic, the fan would cycle on and off a lot...and even if I got a long stretch at freeway speed, it wouldn't cool down like it used to.

I discovered that if I brought it to normal operating temp, then parked for 5-10 minutes and restarted the problem solved itself. On restart, the coolant temp would drop significantly and it would cool itself off again at freeway speeds.

To my mind, this felt like a weak thermostat (don't know if that's a thing, but that's the way I imagined it) so I replaced it.

Now with the new thermostat the quick heating and staying warm even when cruising is back. I've checked and re-checked for bubbles in the cooling system (can't find any). The car isn't overheating, per se, but it does need the fan quite a bit and if it's been cycling a lot on a drive, I'll get a pressure leak from the radiator cap when I park in the garage (it's a new radiator cap).

Any ideas?

[124JOE]

did you flush it when you removed the brown coolant?
you replaced the external thermostat,did a PO install a internal thermostat? there should only be one"ext"
if these are all good you may need a new fan switch located by the lower rad hose on the rad

[So Cal Mark]

sounds like the radiator is plugged up

[wubie317]

Where exactly might that internal thermostat be? Is it sometimes put in the T at the front of the engine facing the radiator?

I saw a pic on the forum, but couldn't really tell what I was looking at.

[131]

Where exactly might that internal thermostat be? I saw a pic on the forum, but couldn't really tell what I was looking at.

It sits under the fitting that bolts to the top of the head. Earlier cars used the in head thermostat, Fiat later went to the external type.

[4uall]

this might help

http://fiatspider.com/f08/viewtopic.php ... g+solution

[wubie317]

I did a test with an infrared thermometer on the hoses and found that after sitting for 20 min or so (it got me home in traffic, so pretty high temps and heavy usage of the fan which was working), the hoses ranged from:

Head tee to top of radiator: 156°
Head tee to thermostat: 172°
Block to thermostat: 172°
Thermostat to Bottom of Radiator: 135°

Is that enough of a delta to wonder whether there's a bad internal thermostat in the head tee? Does the theory that the radiator is bad hold water (pun carefuly considered)? Is the delta big enough to assume that the external thermostat is not open? Can I posit that the NEW thermostat is faulty or stuck? Or could it be the dreaded air bubble that's not letting the water get hot enough where it needs to be hot and opening the valve (so should I drill a small vent in the old one and give it a shot?)
Based on the records I have, I think the PO mechanic was a good, solid. real Fiat mechanic (unlike me ) so I don't think they would have gone and added an internal thermostat in the T, but one can't be positive until one takes the thing apart...which I'd rather not do, based on the fears about the tiny bolts.

[4uall]

Another option is to confirm the installation and flow direction of the external t stat



http://www.international-auto.com/fiat- ... t-flow.cfm

[aaalbedo]

Here's another possibility. PO claimed a brand new water pump, but here is what I found instead.

https://www.dropbox.com/s/mhvzc6upft0ej ... 0.JPG?dl=0

Auto Ricambi pump keeps me cooler than normal now; PO probably installed a low temperature thermostat. Hey, at least he tried to fix the problem!

lw

[wubie317]

Here's another possibility. PO claimed a brand new water pump, but here is what I found instead.

https://www.dropbox.com/s/mhvzc6upft0ej ... 0.JPG?dl=0

Auto Ricambi pump keeps me cooler than normal now; PO probably installed a low temperature thermostat. Hey, at least he tried to fix the problem!

lw

Well, my clutch cable snapped so I haven gotten back to the thermostat yet, but I have a new water pump waiting for the time to do timing belt. Got a long list suddenly! I'll keep you all posted!

[bradartigue]

Good lord - new water pump in 1985 maybe. It looks like it ingested rocks.

In terms of cooling systems on these cars, don't ever over complicate it, the system is too simple, the radiators on these cars are ancient, if you don't know the condition then you may want to have it recored or rodded just to do it. Otherwise most problems are due to not being full of water, goofy senders, or a goofy gauge. When properly filled they rarely, if ever, overheat.

Though 50% of the thermostats are installed backwards.

[mcpeach]

Have you take that infra red thermo to the radiator to check for cold spots/blockages?

[wubie317]

Have you take that infra red thermo to the radiator to check for cold spots/blockages?

I did a test with an infrared thermometer on the hoses and found that after sitting for 20 min or so (it got me home in traffic, so pretty high temps and heavy usage of the fan which was working), the hoses ranged from:

Head tee to top of radiator: 156°
Head tee to thermostat: 172°
Block to thermostat: 172°
Thermostat to Bottom of Radiator: 135°

Is that enough of a delta to wonder whether there's a bad internal thermostat in the head tee? Does the theory that the radiator is bad hold water (pun carefuly considered)? Is the delta big enough to assume that the external thermostat is not open? Can I posit that the NEW thermostat is faulty or stuck? Or could it be the dreaded air bubble that's not letting the water get hot enough where it needs to be hot and opening the valve (so should I drill a small vent in the old one and give it a shot?)
Based on the records I have, I think the PO mechanic was a good, solid. real Fiat mechanic (unlike me ) so I don't think they would have gone and added an internal thermostat in the T, but one can't be positive until one takes the thing apart...which I'd rather not do, based on the fears about the tiny bolts.

[4uall]

it was just 4 bolts/screws for me, should not be that difficult to check, use a magnetic screwdriver if worried

[bradartigue]

The problem with clogged radiators is they aren't really clogged per se, they still flow, but not enough. So the radiator doesn't necessarily heat up any more or less than it did, it just doesn't flow enough water - it doesn't cool down enough volume of water. Hopefully this makes sense.

is your car really overheating or just saying it is overheating?