Stupid car. Can anyone help?

A little additional info would be helpful....like...what kind of car? Year? Miles?

First thing that comes to mind is a "sticking" thermostat....if everything else is in order and it goes back to "normal" without doing anything. Next place to look...possibly a water pump.

 

Stayin' busy!

 

Engine temperature can't change that fast, if I understand your description correctly.

Sounds like a temperarure sensor problem. Try locating the sensor and check the electrical connector.

-

 

Checking the thermostat is a good idea, but I suspect the Engine Coolant Temperature sensor or the wiring to that sensor. The ECT registers low resistance as temperature rises. If there is a short in that wire, it could intermittently be showing zero or near-zero resistance, intermittently. I'd check the wiring first, looking for worn insulation that could be touching metal somewhere.

Could also be a bad sensor, and they're generally cheap and easy to replace.

 

I agree with checking the thermostat. You may also need a new radiator. Do you fill it with anti-freeze or water? Has the car been running rough since this has happened. You can blow a head gasket when you overheat your engine. If that has happened you won't have as much compression and you will see water in your oil.

 

This and the left indicator could both be electrical problems.

FWIW, I had a squirrel eat a bunch of wires in my vehicle a few years ago. I repaired it myself, and while it took a fair amount of time, it wasn't particularly expensive.

 

More good advice!

 

A malfunctioning thermostat can cause that. It sticks and the temp rises and then opens to bring it back down.

 

I would suspect a short circuit or a loose wire somewhere in the coolant temperature circuit, but replacing a thermostat is so cheap and easy on most vehicles there's not much reason to start anywhere else.

 

It's a wiring or electrical problem..

Engines don't overheat and cool down that fast........not even close....

If your turn signal also comes on by itself.....the two could possibly be wiring related.....

I highly doubt it's your waterpump or thermostat.......

 

A new thermostat will probably cost less than $20. Changing it out is not too hard. The hardest part is getting at the darn thing. Once you have access to it you're in. Here is a video about changing a thermostat on a Peugeot. It is a different year and model than yours but it is the same basic idea. Probably not too different than yours. You can find specifics online or at the library. It may not be the thermostat but if you feel you are up to it you might want to see if that fixes the problem.
Changing the thermostat starts bout 2:50 minutes into the video.

 

I wonder if Colombo ever had these problems with his Peugeot?

.

 

If you have a blown headgasket, you'll more than likely be noticing lots of coolant loss.......

 

Given the fast rise and fall of the temp indicator, my vote is for one of two things, in order of likelihood:

1) Bad temp sensor (bad wiring is not likely)

2) Thermostat sticking

Number 2 is unlikely because coolant temp doesn't go up and down in a few seconds. It can't. it has to take time to circulate around the radiator and block. I'd see if I can find the wire that connects to the temp sensor, ground it and see if the gauge maxes out. If so, I bet the sensor is doing the same internally. In any case, I'd replace the sensor and see what happens.

Now all you need is to find a 70-year-old French mechanic to open the hood on the Peugeot.