How can you tell if thermostat or water pump are faulty?

[ObedP]

Hello everybody. Hoping your skodas are behaving fine. This is what happened to me: I was driving my felicia when I noticed the temp gauge went high to the top, then it went down and never worked again. I was returning from fixing a leak I had in one hose, the one beneath the radiator. I replaced it with a new one, and checked all the other connections. Now I didn't have any leaks, great! But then it happened what I just described above. The thing is that I decided to purchase again the temp sensor, tested before installing it and the temp gauge responded accordingly. But now i'm afraid that the new temp sensor will be damaged if there is a fault in the cooling system, so I have not installed it yet until be sure. How can I know if the thermostat is not stuck closed or open, or the water pump is working? Thank you for your time.

Edited 16 May, 2016 by ObedP

[jonnycilia]

if thermostat is stuck open, it will take ages to warm up. if its stuck closed it will overheat pretty quickly. the felicia plastic thermostat is known to cause issues (mine broke internally and stuck open all time). water pump usually when going out will overheat the engine also. and it will maybe leak past the hole it has in it if its so worn. but im not sure

[jonnycilia]

butt if you say it never worked again, i would say try the temperature gauge because it sometimes gives false readings. because of course if the engine did really overheat it would have stayed in the hot area of the gauge, not stop working.

[RicardoM]

The coolant temperature sensor (CTS) can't fail from a faulty cooling system. It's a double thermistor rated from -25C to 130C. The CTS fails either naturally from aging or from using low quality materials. Moreover, I think that new aftermarket sensors are designed to fail. So I don't see any reason why you shouldn't use it.
 
Water pumps for Felicia usually don't fail in the sense that the impeller doesn't rotate anymore or the blades break. I don't exclude the possibility that some cheap VIKA pumps might break from bad materials or bad casting. The pumps fail most often when the axial seal or the bearing wear out. The pump will start leaking in the former case or will become noisier in the latter.
 
You will learn a lot more by reading my post here.

 

The easiest method to check for a good thermostat is to feel the temperature of the thick hose between the thermostat housing and the radiator.

 

Stuck open thermostat - the hose warms up gradually before temperature gauge needle starts moving. It takes a very long time for the engine to reach 90C.

Stuck close thermostat - the hose stays cold all the time and the engine overheats.

Normal operation - the hose stays cold to about 82C then start heating up quickly.

[ObedP]

Thanks  for the answers. Then I think I have a stuck open thermostat, cause I installed the new temp sensor and have been driving the car for a couple of days, but the needle stayed down, below the 70C. The hose between the radiator and the thermostat is pretty hot, so I thought the temp sensor was faulty. But yesterday the day was pretty hot, and finally I saw the needle going a little bit up, would say like 75C. Normal operation would put the needle at 90C always?

[RicardoM]

Normal operation would put the needle at 90C always?

Yes. At 90 deg C the engine has best performance.

 

I wouldn't be surprised if there is no thermostat at all on your car...

[ObedP]

lol you're right! I will check. Let you know.

[jonnycilia]

mine was without a thermostat installed and took ages to warmup. then after i installed a new genuine thermostat and a genuine housing it worked great. it was junk anyways because the housing was cracked

Edited 24 May, 2016 by jonnycilia

[ObedP]

Thank you Jonnycilia. I will do the same soon. I hope the housing is fine. But anyways, the fan kicks in as soon as I start the engine, I have been using coolant, no leaks, the temp sensor gauge goes up a liitle bit, like 75-80C sometimes. Am I at inminent risk?

[jonnycilia]

worry only if it goes above 105 degrees with the fan on and still going higher to the red line

[RicardoM]

The only "imminent" risk you're facing is a high fuel consumption. An engine running cold is inefficient.

 

As for the radiator fan running immediately after key on, you got a very good answer in another topic opened by you.

[HeavyMetalRich]

Has your coolant level been dropping at a steady rate?

[ObedP]

No, coolant level remains the same.

[ObedP]

As for the radiator fan running immediately after key on, you got a very good answer in another topic opened by you.

That answer I got from that friend took for granted that I was using de AC, which is false. I have never used it so it is always turned off. So the question remains unanswered. But I will add this information to that specific topic so someone helps me find the reason why the fan kicks in as soon as I start the engine.

[RicardoM]

I know you didn't use the A?C but the symptoms are as if the A/c button is pressed. Check with an ohmmeter.

I don't remember if you have all electric parts of the A/C on the car. Make an inventory and tell us what is present and what is missing.

Edited 26 May, 2016 by RicardoM