Engine not fully heating up

[Pinnacle100]

My 1.6 tdi seems to struggle heating up fully . It CAN heat up to 90 degrees but does take a while especially when it’s cold weather but even when it’s not cold outside sometimes I can drive for 40-50 mins and it’s still not at 90 degrees , the needle on the temperature dial just hovers about 1/4 of the way round .
Whenever the temperature does decide to get to 90 as soon as I slow down the temperature quickly drops again and can take ages to get back to 90 degrees.

Anyone have any thoughts on what I should be getting checked?
All I can say is that my Coolant level has never dropped so I definitely have coolant in the van so I know I’m not leaking coolant. Apart from that any advice would be greatly appreciated.

[the swan fiend]

My 1.6 is quite slow to get to temperature too, like you I’ve checked everything out and all seems well. I can sit at anything from 55 to 65 mph on the motorway for my 13 mile drive to work in anything from 4 degrees or so and cooler and it only gets up to 80 or 85 degrees.
The only thing that bothers me about it is I’m not sure the DPF will regenerate if it’s not upto the full 90 degrees, so I normally make sure I give it a faster run when it’s a bit warmer.


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[BenT]

Sounds like your thermostat's stuck open. Most of my TDIs have had this happen at some stage. They normally only cost a few pounds and take less than half an hour to do. That said, I've never done it on a 1.6 before and it's not the simplest under-bonnet! If one of the coolant hoses going to the radiator is warm/hot before the temperature display's got to 90 degrees this is very likely the problem.

[NZDubNurd]

Yep. Thermostat issue. The gauge reads 90c once the engine gets to 75C, so if it's hovering under "90", then the engine is really only in the 60's or early 70's.

You can cheak the actual temp in VCDS, or on the Climatronic secret menu, if you have dual zone climatronic system.

[DeanWhit]

Glad you’ve posted this as mine is doing the exact same thing. Booking it in at the garage on a Monday.

[Pinnacle100]

Thank you all for your replies.
I had a look at some videos on changing the thermostat but it looks a bit out of my comfort zone so I’ll need to get it into the friendly local mechanic. DeanWhit please let us know how you get on with yours .

[samyam1]

Sounds like my issue too.

Get up to 90 but if you stop with the engine running it drops down again. Going to be a job for this week whilst it’s quiet at work.


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[DeanWhit]

Update!!

Had at least one of the coolant temperature sensors changed on Friday. Just been out on the motorway and a bit of driving around town and it’s doing the same thing. Temp gauge barely got up to half way.
Any ideas?

The heaters aren’t particularly blowing hot, just warm really.

[Dave_c85]

Sounds like the stat is stuck open. Had this on mine a while back, pretty hard to access so labour charges were significant!

If you turn the heaters on max heat and max flow and the temp drops it's a good indicator of stat stuck open.

[DeanWhit]

Is the ‘stat’ something different to the coolant temperature sensor that I’ve just had changed?

[Dave_c85]

Is the ‘stat’ something different to the coolant temperature sensor that I’ve just had changed?

Yep, thermostat will open and close to bring the radiator in and out of circuit. It's closed when engine is cool and once engine gets up to temp it opens to send the coolant through the radiator. It'll then open and close as needed to keep engine temp in check. If it's stuck open it's always sending coolant to the radiator so in effect over cooling the engine (better than being stuck closed which would cause overheating), hence why your temp on dash is low. The temperature sensor just reads coolant temperature.

[DeanWhit]

Brilliant, nice one.

[PeterAFox]

If you want to DIY:
here OEM thermostats sell for 12-15€ (at least for mine)
biggest hassle is that the coolant needs to be drained - for me this means axle stands and buckets.
Technically it's not difficult - the thing to really check is that the new thermostat is seated correctly with washer etc. before refilling the coolant

[DeanWhit]

Booked in for the 24th. I get the feeling it’s going to be an expensive one

[dangoesfast]

Thermostats are cheap and extremely easy to replace (apprentice work), if it's an expensive one then I'd look for another mechanic.