Jiggle valves & thermostats

andybaggies

andybaggies

A2OC Donor
Had the usual temp gauge troubles on my TDi and after first replacing the sensor the gauge was still giving erratic readings. So I bought a stat from Euro Car Parts but during fitting noticed it had a jiggle valve whereas the old one didn’t - one of those small brass “keys” that’s allowed to jiggle in a hole in the stat’s facing plate. Hmmm, but had no option but to fit it.

Took him for a quick blast, on one of the hottest days of the year, and the gauge got up to 90 and stayed there, sorted.

However over the next few weeks I noticed it would take ages to get up to 90 and suspected the jiggle valve was to blame. So bought another stat, this time from AVS parts without the jiggle valve, and this halved the time it took to get up to max, hurrah, unfortunately the max is now a stubborn 88C…..

Also both stats weren’t a great fit in the housing pipe, either too tight against the centering lugs or unable to hook under the locating tabs.

So would a stat from a dealer be any better?
 
I fitted an OEM Audi thermostat into my cousin's A2 the other weekend and can confirm it fitted snug as a bug in a rug, plus it brought the car up to 90 much more quickly than before - their old 'stat was borked, as was their coolant temp sender - completely coated in mineral deposits.
 
Thanks for confirming Dan, was this on a AMF as I wonder if the pipe/stat has changed? Either way others beware that supposed OEM replacement stats aren't always what they say they are and independent garages could just as easily order and fit the same.

I'm hoping a max of 88 won't have a big (or any) hit on fuel consumption but can see it becoming one of those seriously irritating but inconsequential matters :mad: So how long will it take before I change the stat for the 3rd time?
 
Did you replace the coolant temperature sender as well? Have you got VCDS or another app like Torque, or Scangauge that actually lets you read the coolant temperature output directly ?
 
I initially did only the sender and after a week or so of still erratic gauge readings did the stat. The first stat did ultimately go to bang on 90 but I do find it strange that a stat can effect such a small but permanent 2 degree difference. Air lock perhaps?

Yes I do have VCDS but only lite - not sure if it can do a real time temp check. Good thought though & I'll check tonight.
 
I've read that car manufacturers 'condition' the temp sensor output so the gauge reads 90 even though the actual coolant temp could be several degrees either side of this. Apparently it reduces warranty work and owners like to see the rock steady reading.
VagCom should display the actual coolant temp from the dual temp sender which is used by the ECU for fuelling and injection timing and this is the only way to understand how the thermostat is operating
For info, a genuine stat is about £30 but Skoda dealers on e.bay sell them for significantly less. Double check but I think the p/n is 044121113
A jiggle pin is used for venting air from the cooling system when the stat is closed (when filling with fresh coolant etc) The pin is then forced shut as coolant tries to flow through the small hole. They only really work in vertically mounted thermostats so they are not really designed for an A2

Cheers Spike
 
Spike, I think the p/n is correct as this lines up with the two I bought. So the first one I bought took an age not because of the jiggle pin allowing coolant through too early but because of the opening characteristics of the stat itself?

I paid around £10 for each of them so this looks like a case were genuine is best.

Looks like lite does do the measurement blocks and I'll check the coolant temp when I get into work tomorrow morning.
 
AndyB, as you propbably know, the stat is opened by a wax capsule. Actual opening temps are fine tuned by crushing the body of the stat to optimise the volume of the wax cavity. This may not be done on cheepo stats. Poor sealing of the stat in the closed position may also extend the warm-up time, as would a poorly seated jiggle pin.

Cheers Spike
 
Well it's to know nice to know the sender and gauge are working in unison as VCDS gives the coolant temp as 88.2. I can't believe the fueling is any different than it is at 90, could it?

I'm a little chuffed off with myself as I don't normally do cheapo but never thought stats would be so precise. Lesson learnt and 3rd coolant change in 6 months??

Andy B
 
There are some people playing around with higher temperature stats on the TDIclub forum, in order to try to get slightly higher mpg. Seems a little risky to me, not much margin for error unless you're using a non-water coolant such as Evans.
 
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