Temperature gauge weirdness

[neilb740]

I took my ZT on its first long run for ages this weekend, a 150mile run down to Bristol.
Im not usually one for tearing around at break neck speeds, usually pootling along about 60/70ish but on an empty M5 early in the morning I decided to put my foot down a bit.
I was cruising along at about 85mph (sorry to all you anti speeding people) and everything seemed fine until I glanced down at my temp gauge and saw it had dropped to practically zero.
Gripped with the usual coolant paranoia all us 1.8 owners have I immediately backed off and planned to pull off at the next possible opportunity.
As soon as I did the temp gauge climbed back to normal and stayed there.
I pulled off at the next services anyway and after letting it cool down did all the usual checks. All were O.K

I tryed this several times during the journey, always with the same result. Go above 80/85ish, temp gauge plummets. Reduce speed and it climbs back to normal.
Any ideas??

[dissy1810]

Does your car have the prt ? as it opens more with higher revs

[neilb740]

Originally Posted by dissy1810

Does your car have the prt ? as it opens more with higher revs

Im not sure, and not sure what to look for. is there a way to check??

[dissy1810]

Look to the bottom of the radiator air filter side and the pipe should go into the prt if you have one it is usually black or cream and has three coolant pipes on it

[neilb740]

Originally Posted by dissy1810

Look to the bottom of the radiator air filter side and the pipe should go into the prt if you have one it is usually black or cream and has three coolant pipes on it

Thanks, I will look as soon as I get home. Just doing a bit of "market reserch" on the work computer at the moment lol

[T-Cut]

The simplest way is to look at the large radiator hose from top left to right side of head (as you look at it). There's a joint in the middle. If a PRT is fitted, the joint is the infamous T-piece. The down leg of the T goes to the PRT. In turbo engines, there's a small bore pipe coming from the armpit of the T and goes to the turbo.

Turbo T-piece for PRT



Underneath (with undertray removed) this is where you'll find the PRT.



TC

[catmandu]

A possible cause is an airlock, you need to fill the coolant in a specific way, I think that there is a howto to show you the right way

[Parker]

I had this similar issue a few years back with the standard 1.8, on my journey to work when picking up speed the gauge would drop and like you paranoid. I did a battery reset as was advised at the time on here and the issue was resolved, never had it again.

It may have been a coincidence or it could have cleared a gremlin or two, just something else to consider

[chrissyboy]

Originally Posted by Parker

I had this similar issue a few years back with the standard 1.8, on my journey to work when picking up speed the gauge would drop and like you paranoid. I did a battery reset as was advised at the time on here and the issue was resolved, never had it again.

It may have been a coincidence or it could have cleared a gremlin or two, just something else to consider

happened to my 1800 turbo ,dropped to zero for no reason at all ,i checked the car over and found nothing wrong so put it down to the ecm gettings its knickers in a twist , like you it never did it again