Death of my thermostat

[mtroxel]

Lately my gauge rarely get's to 12:00, usually hangs out at maybe 11:45-ish. Logged my temps from a cold (12˚C) start on a 20 minute drive this morning. Looks like it first opened at 78˚, then muddled around till it finally let it hit 79˚ a couple times. Never even got to 80˚. I assume this stat is supposed to open closer to 90˚C?

[allstock]

Highest I've seen is at mid 90's.

If that's your current mileage then it's about the right time to change.

[shahk62]

Could it be the sensor? Most shops replace both at the same time


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[Okedokey]

I really wouldn't worry about that and relog in summer.

[adam044]

If it's not getting to the middle it's bad. Don't need logs to tell you that.

[mtroxel]

Could it be the sensor? Most shops replace both at the same time

According to RossTech, If it's the sensor it will read -40˚ or +140˚. Anything between 68˚ to 80˚ means the sensor tends to be fine but the stat is blown.

I read somebody's DIY, how long is this going to take?

[oVeRdOsE]

According to RossTech, If it's the sensor it will read -40˚ or +140˚. Anything between 68˚ to 80˚ means the sensor tends to be fine but the stat is blown.

I read somebody's DIY, how long is this going to take?

to do the thermostat?

I took me about 2-3 hours, because I miss some important steps in the timing belt DIY.
should take around 1h30 to 2 hours if I had to redone it.

1- Unplug the battery
2- remove alternator ( 4 hex bolt) ( alternator can hang there, no need to unplug the cables)
3- remove the little screw on the thermostat that hold the rigid hose to the oil cooler
4- remove 2 screws holding the thermostat
5- remove the 2 hex screw right over the oil cooler ( if not, you won't be able to remove the thermostat because of the rigid hose)
6- remove the 1'' rubber hose ( can be hard, sticky and clamps are not easy to slide.)
7- remove the main radiator hose , remove metal clip completely ( pull with flat screw driver ) and then do not twist , just pull . It's a pita because it's fragile and it's hard to remove. flat screw driver can help.
8- pull the thermostat out ( removing the air intake hose can help)
9- Be very careful, you have 2 rubber o-ring (main one to the engine block and small one on the rigid cooler hose)
10 - The main o-ring is very easy to break! use grease/vaseline, it will help to slide the o-ring on the block without cutting it.

[mtroxel]

Thanks oVeRdOsE, but I think I'll add a step and drain the coolant somewhere early on. Since that system drains so poorly, I assume some coolant is just going to dump on the floor when you pull hoses off the stat?

[oVeRdOsE]

Thanks oVeRdOsE, but I think I'll add a step and drain the coolant somewhere early on. Since that system drains so poorly, I assume some coolant is just going to dump on the floor when you pull hoses off the stat?

right.

You'll need to access the drip valve at the bottom, next to the hose connecting the thermostat and radiator.

Removing the driver-side intercooler bottom hose will help. No need to remove the skid-plate. (7mm to loose hose clamp)

It will drip about 4L of coolant.

Shitty step : buy a thermostat AND collant (plain G13 or G12 + deionized water)

[mtroxel]

You'll need to access the drip valve at the bottom, next to the hose connecting the thermostat and radiator.

Unfortunately, I think that only drains the radiator and the coolant tank. The block is still full if I recall right.

[oVeRdOsE]

Unfortunately, I think that only drains the radiator and the coolant tank. The block is still full if I recall right.

yes, that why it's only 4L .

I did the timing belt and then by removing the water pump, more hoses on the engine and around the turbo, I drip few ml more.

at the end, I used 1.4 to 1.5 gal of my 50/50 mix. So : 5.5 L new coolant, I have about 1.9 L left in the coolant can.

Coolant is always good, I will transfer heat , old or new.

The issue here, is the PH change over the time and over the use. It will come more acid and can degrade the engine internals faster.
And you will have debris in the coolant due to the engine part wear.

I'm considering mine almost all new. I will flush it on the next 90 000 km.

( I did not use coolant flush additive, should I? Maybe... there's some people are doing it and some not. )

[adam044]

Get the coolant from the dealer.

Probably 2-3 hours

I didn't drain the coolant at all when I did mine. As you pull the hoses off of the thermostat it will come out. Makes a mess but it's low in the engine bay so it's whatever as it doesn't get coolant on much, it will just burn off any ways on whatever it gets on.

[adam044]

Could it be the sensor? Most shops replace both at the same time


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There's 2 sensors

[B72011]

I was having a bit of seepage--so using a suggestion from Youtube Audi repair guy EXOVCDS --I just swiped on a thin layer of rtv gasket to the orings. Works money. I didnt need it the first time I did the job, but the 2nd time I just couldnt get it right. Either way a very easy job---one that got me started on car repair! Thanks to Phil for his DIY that got me going. That engine rebuild thread also got me pumped that I could do a motor rebuild--maybe too psyched out though hahhaha. It was made to look so easy.

[Theiceman]

this one :

shows you real time ..

https://www.youtube.com/watch?v=ixyRYG44lfs

[JesusB7a4]

My gauge would also go from 12 towards the cold area. Changing my thermostat was a pita because I think the last owner or shop that did work on it stripped the triple square bolts. Make sure you have the o-ring for the center hose on the thermostat. I almost did mine without it since it didn't come with it when I bought it.

[Theiceman]

My gauge would also go from 12 towards the cold area. Changing my thermostat was a pita because I think the last owner or shop that did work on it stripped the triple square bolts. Make sure you have the o-ring for the center hose on the thermostat. I almost did mine without it since it didn't come with it when I bought it.

I had trouble finding that o ring. Is it available at the stealer ?

[mtroxel]

I had trouble finding that o ring. Is it available at the stealer ?

Yep. Bought it yesterday. $4.50. Cheapest trip to the dealers parts counter since I bought some O rings for the AC on my B5.

[mtroxel]

Finally did the new stat. Gauge points right straight up now, and in fact heats up much faster. Nailed it!

[Sanjman]

Easy money! Thanks for the update. This helps confirm the countless threads where people want to blame the CTS but ultimately ends up being the thermostat.

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[BenMTL]

Finally did the new stat. Gauge points right straight up now, and in fact heats up much faster. Nailed it!

107000 miles and first time you replaced the thermastat?? Wow, yours lasted long

Mine gave out (similar symptoms) at 78000 miles...