Hi, my octavia 1.6 tdi 5 speed manual 2013 has recently got 2 faults, I think they are related. When I start the car in the mornings the revs jump to 1800 rpm for a sec and then idles at 1100 for a min, then comes down to normal (750ish). It only does that the first time I start the car in the day.

I do a lot of miles a day and realised my coolant temperature stays at 50 degrees even if I've driven all day. It sometimes goes upto 65 degrees for maybe a 30 secs and then goes down back to 50 degrees. Shouldn't if stay at normal optimal temperature at 90? Getting paranoid if my car is overhearing and not showing. But when I check the engine oil temperature it sit between 92-97 which looks normal. So I'm thinking if theres a problem with the coolant/ temperature sensor (does it have one) and where is it located, or maybe faulty thermostat if it has one again lol. Sorry for my long post and any help and guidance would be grateful. 

Thermostat or water pump switch over sleeve stuck open.

Edited 21 July, 20196 yr by MoggyTech

The first sequence you mention applies to many vehicles starting from cold. Our new Picanto does that and my 1.4Tsi does it especially in colder weather - but not for long. It's not a problem. 

1 hour ago, MoggyTech said:

Thermostat or water pump switch over sleeve stuck open.

 

Hear, hear. One of my tranny vans had the same issue. On cold days, it wouldn't get warm and was eating fuel. It was diagnosed as a thermostat being stuck open.

 

Would answer why the revs are going up and down as well.

 

I'd get it into the garage as soon as you're able to, as you're engine won't be running happy.

Thanks for replys everyone

I changed the water pump and cam belt 11k miles ago! Cant be messed up soo soon. By the way where is the thermostat location on the 1.6 tdi??

Doesn't it have a coolant/ radiator sensor also?

7 hours ago, HAKS360 said:

Thanks for replys everyone

I changed the water pump and cam belt 11k miles ago! Cant be messed up soo soon. By the way where is the thermostat location on the 1.6 tdi??

Doesn't it have a coolant/ radiator sensor also?

Does the heater work. Is it hot or only lukewarm?

There may be several thermostats ie cooling circuits  for a progressive warm up. Sorry, I do not know any more.

FIXED!!!

its was the coolant temperature sensor! Now the temperature gauge on the dash reads normal (90°)

Ps all the hot, cold, air con temperature, fan speed inside the car was normal.

The sensor is located underneath the air filter box, by the gear linkages

21 hours ago, HAKS360 said:

FIXED!!!

its was the coolant temperature sensor! Now the temperature gauge on the dash reads normal (90°)

Ps all the hot, cold, air con temperature, fan speed inside the car was normal.

The sensor is located underneath the air filter box, by the gear linkages

Good to know. Thanks for sharing. 

On 24/07/2019 at 11:52, HAKS360 said:

FIXED!!!

its was the coolant temperature sensor! Now the temperature gauge on the dash reads normal (90°)

Ps all the hot, cold, air con temperature, fan speed inside the car was normal.

The sensor is located underneath the air filter box, by the gear linkages

Nice result. I changed my sensor and it didn’t make a difference. Changing the thermostat now next week. 

On 24/07/2019 at 11:52, HAKS360 said:

FIXED!!!

its was the coolant temperature sensor! Now the temperature gauge on the dash reads normal (90°)

Ps all the hot, cold, air con temperature, fan speed inside the car was normal.

The sensor is located underneath the air filter box, by the gear linkage

Happy that you fix your problem. Was it showing any faults on the computer or check light going on because of the faulty sensor?