Temperature dropping at high speed

[MPH]

Hi all just had full timing belt kit crank and cam seals water pump rollers aux belt etc 90 degrees around town on point but temp gauge fluctuates at high speed up and down but does not go above 90 so not over heating. Maybe thermostat getting stuck open car appears to be running normal apart from temp gauge at speed.Checked for air locks heater matrix o.k! everything was fine before no issues constant 90 degrees got direnza rad 10 months ago all fine until now, vcds do not throw any codes any advice appreciated thanks MPH.

 

[pyle]

Most likely thermostat stuck open, the car cools down from the air being pushed.

 

[MPH]

Most likely thermostat stuck open, the car cools down from the air being pushed.

Thanks mate all symptoms lead to a dodgy thermostat but just had it back from the garage asked me to monitor it change back to my Audi coolant cap instead of the Porsche one.

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[pyle]

Why's that suspected air leak?

 

[MPH]

Why's that suspected air leak?

Indeed just bought new thermostat coolant ball see how that goes! although other one appears fine changed cap on a 25mile run pressure seemed o.k soon as the weather picks up out with the old stat.

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[hydro s3]

Where you using coolant with the coolant bottle not being pressurised?
Reason I'm asking is my car has started to lose coolant and have to keep topping it up about every 2 weeks and was told it could be my cape not sealing correctly. It's just the normal cap i have on mine.

 

[MPH]

Coolant bottle is pressurising fine with all three different caps Audi Porsche and Febi. The top coolant sensor maybe had it leak giving these symptoms several times as the housing tends to warp or o ring fails or sensor itself upgraded to aluminium housing to sort that one out.

 

[pyle]

If the system is leaking it can cause an air bubble in the block and crack the head gasket, get it fixed as soon as possible.

 

[hydro s3]

@pyle was that message about the head gasket a reply to what I wrote?

 

[Chicken Hawk]

Does the engine take longer than normal to warm up? If the cooling system is holding pressure and hasn't any air locks or leaks, I’d say check/replace the thermostat

 

[MPH]

Does the engine take longer than normal to warm up? If the cooling system is holding pressure and hasn't any air locks or leaks, I’d say check/replace the thermostat

Car takes 8 minutes to warm up to 90 degrees no airlocks or leaks pressure seams o.k