Temp gauge wandering on TFSI 2L Octavia RS after new water pump and timing belt

[woofy]

Had the 107k/7yrs major service where they change the timing belt, some other bits and also the water pump. Its a late 2008 Octavia RS so the TFSI 2L engine. It;s my wifes car so I drove it too and from the servicing, but haven't been in it since. I noticed when taking it out tonight that it took longer than usual to warm up, and once it did, it hit the usual 90C mark (dead vertical) where it normally stays. However it actually dropped a bit, and then crept back and did this for about 10k. It was about 20C outside at night and doing 60 and 80k/hr on pretty quiet roads. At one point I took off and it dropped down to the next marker and then crept back up. I parked for about 2hrs and it warmed up pretty quickly but noticed it would drift to the left a bit and then come back. It never got hotter than it should.

When I got home I popped the bonnet and didn't notice anything untoward, although the overflow container was filled well above the min/max line, well up to where it says G12 on it!

I also noticed that the airintake wasn't connected properly at all to the engine cover, guessing that isn't a big deal as the clamp clearly wasn't pushed back so it slipped, I'm guessing the air filter is further on under the engine cover. Never really looked at that before, but was surprised when you looked through the front intake you can see through to the firewall! I'm wondering if they were that sloppy with something obvious, what they might have missed or caused to make this moving temp. From what I remember the needle kind of artificially sits bang on vertical/90C but have never seen it cool down over time!

[woofy]

I'm wondering if it's the thermostat, but also now sus if they left some air pockets in there. It didn't do this before they touched it so unlikely the thermostat and the higher coolant level makes me think that may be the culprit.

[Umai Naa!!]

These motors are always tricky with getting the air burped out of the cooling system.

Keep an eye on it for the time being.

[brad]

I was thinking air pockets. You might have to vent some pressure from the overflow when it's hot to help burp it. Be careful - hot fluids under pressure, etc

My guy always fills the overflow about 25mm above the halfway point.

[woofy]

Yeah the coolant is well above the two lines, and above the midway mark just near where the G12 is written on it. Wasn't before the service, it was just above the higher of the two marks.

[h100vw]

Not a 2 litre but my Polo always burps twice when you have done a full drain on it. You can do one o the drive but it always needs a trip around the block to set the second one off. I always do that run with a top up bottle on board.

Running under temp could be a thermostat sticking open intermittently.

Gavin

[woofy]

Took it in as the air intake was resistant to getting out back on, and we were going near the dealer. They checked engine codes and tested the probes which seem ok. Went for a test drive in stop start traffic though so didn't see the issue. I did the whole way there.nsawvit the minute I drove out and hitting the freeway at 100 caused it to drop to the next mark and stay there until stop start traffic again. Pretty repeatable. Have booked it in early next week for a check over again.

[woofy]

Took it back today and the test driving guy saw it before even leaving the yard with me there, and said it is obviously the thermostat being stuck open. We still went for a drive and there was no doubt. Lucky it wasn't being stuck closed, he reckoned it was a random coincidence that it happened straight after the belts, water pump and coolant were changed. I can't see how it could be totally related, but there is no doubt it happened straight after. I don't know the mechanics of this type of thermostat but is there any way something could be stopping it from closing after being flushed out, ie some crap got stuck in it? Been told its a $500 repair so not really happy about it. The car has just hit over 7yrs old but is only just on 70k so would expect better. It feels like they are doing the easy fix for them, but if I am correct, I'm betting it has some crap stuck in it, and they would be reluctant to tell me.

[woofy]

New thermostat replaced, cheap part ($110), but its a bugger to get to them, and the dealers of course will pull everything off rather than do it the more trickier DIY way with extension sockets. So far so good, cold weather here today and the needle didn't shift. I'm still wondering whether something was obstructing like debris from the coolant change recently, but they didn't say anything.

[woofy]

Oh this just gets better. My wife rings today saying she can smell something bad and there is a really bad noise. Open the bonnet to see the engine cover flapping about. Has a nice crack across it and is loose. Thanks guys for that. Have a poke around and realize it goes nuts when the a/c is on, the larger of the twin fans which is underneath the air intake has a chunk missing out if it's out edge. I find it lying where the car was before it moved. Yep the fan is wobbling all over the place causing a big vibration. God knows where that bit was flung to and what it hit but it has some nice chunks out of it before it broke right off so hit a few things at high speed for sure. The dealer closed right when I rang them....car is sitting in the schoolyard for the night.

[woofy]

I should clarify, by chunk I mean 4" of the outer circle of the fan is gone. I have the piece as it was just behind the car so fell or shot out when I opened the bonnet. My guess is some bright spark either broke it when they did the their thermostat repair (last time it was driven before today). It's possible it may have even been cracked in the major service in dec but who knows. The air intake above it was disconnected at the engine cover end after that one but don't think it flops that much to touch there. Unless the dope who reconnected that slipped last week and broke it then.....sigh. I don't think the car is drivable in this state so will have fun tomorrow going through this. I'm also flat out at work and having surgery on wed so perfect timing all around.

[woofy]

My first ever towtruck this morning. The irony is I tend to fix and notice things before they get to breakdown stage, and by getting the waterpump replaced when they did the belts, it's caused me trouble ever since. Getting a new set of fans put in, and I guess a new engine cover after whatever happened to the original during the repair last week.....