Help! Temp sensor replaced now reads lower!! Genuine VAG

[kahunajb]

I've got a very similar problem with mine and have already replaced both temperature sensors to no avail. Will give this a try before I bite the bullet and replace the main thermostat. Do you have a part no. for the bypass thermostat please?

[Human Joist]

So I take it with these. If the temp takes ages to get there but once it does it stays at 90 were thinking the small thermos. If it gets warm quick enough but then can't maintain the temp at 90 it's the main thermo. And if it takes ages to warm up and then can't maintain the temp it's all three. Have I understood it right

[MPS]

I've got a very similar problem with mine and have already replaced both temperature sensors to no avail. Will give this a try before I bite the bullet and replace the main thermostat. Do you have a part no. for the bypass thermostat please?

Just had a butchers on ETKA, the part no. of the bypass thermostat (or coolant regulator as ETKA calls it) is: 4E0 121 113, approx £22 (I haven't updated the price database on ETKA for a while so it's out of date).

 

[Itguy]

Ok, finishing the story for completeness - I've replaced both of these bypass thermostats today and now my temp goes from ambient (currently 5c) to 90c on the gauge in 5 mins flat and then is rock solid.

If you think you have problems you can remove these bypass stats really easily and just test them in a pan of water.

If you take them out try blowing through them first of all at normal air temp. They should be shut. They should start opening at about 77c and be fully open at 88c, co-ordinating with the main stat opening.

[Itguy]

So I take it with these. If the temp takes ages to get there but once it does it stays at 90 were thinking the small thermos. If it gets warm quick enough but then can't maintain the temp at 90 it's the main thermo. And if it takes ages to warm up and then can't maintain the temp it's all three. Have I understood it right

Well what I found was that with both bypass stats failing it just took ages to get to 90 but when there it held it ok.

One bypass stat failed (ie fully open), dsg one in my case, temp would get to c.75 and then climb very slowly from there.

[Itguy]

Yep, thats the ones I bought. I paid £46 inc vat for both from TPS retail prices.

I've got a very similar problem with mine and have already replaced both temperature sensors to no avail. Will give this a try before I bite the bullet and replace the main thermostat. Do you have a part no. for the bypass thermostat please?

Just had a butchers on ETKA, the part no. of the bypass thermostat (or coolant regulator as ETKA calls it) is: 4E0 121 113, approx £22 (I haven't updated the price database on ETKA for a while so it's out of date).

 

[xjay1337]

So you have the main thermostat for the engine and then the 2 additional thermostats.

The other 2, are they BOTH 4E0 121 113 or do they have different part numbers.

[Roadrebel]

The other two are both the same.

[Human Joist]

Right. Two bypass thermostats will be in stock at VW tomorrow. Is there a guide for replacing these at all. Or can someone tell me what I need to remove, time it takes, with any photos. Would really appreciate a few pointers before I do the job Sunday. OR if there is a guide somewhere I can't find it.

[xjay1337]

Looking at the pictures it doesn't seem too hard.......

2 pipes going to a valve which is held on with clips.. I would imagine undo the clips either side and they come right out. 

[v4rley]

Best bet is to start with the one near the dsg, it's the easier on so can be good for gauging knowledge.

The one behind the front radiator, I removed the throttle pipe from between the n/s intercooler and TB. Then removed bottom hose from thermo from underneath the car. Then I undid the coolant hard pipe connected to the inlet manifold and could the pull up the hose with the thermo on the other end to easily release the top hose from it. Replace thermo and do reverse

Take a bit of time to remove the inlet pipe but good prep make the job quick / easier in the long run.
That was how I did it, perhaps easier ways, but maybe of some use

[xjay1337]

Surely you don't need to remove the TB to get to the pipe 

[v4rley]

Surely you don't need to remove the TB to get to the pipe 

Erm no, just the silicone pipe connected to the TB 

[xjay1337]

  misread

[homesqueeze]

Sorry to resurrect this, but I thought this would be the relevant place for good info 

Anyway, I have had the secondary inline thermo replaced and it's worked wonders for my slow warm up. Up to temp steadily in 3-4 miles now. However, occasionally the temp will drop back fractionally to about 88 degrees and then go back up. I'm guessing this means I'm gonna have to change the main thermostat as well? Opinions please.