MadUsa1

I've had a zerosports thermostat fitted to my Hawkeye STI.

It works fine in warm weather but when the weather drops below 5°C for some reason the water temperature falls drastically.

If I'm driving in town it's usually fine but if I drive on the motorway at say 80mph, the water temperature falls right to the bottom of the dial.

Why is this?? I thought the thermostat is supposed to close below 70°C, but it just seems to be open the whole time.

Anyone else had a similar experience with uprated thermostats???

Jay m A

iTrader: (2)

What dial is this? If its OE I wouldn't be too concerned, the range is very small and centred around 90C ish IIRC, 70C may well be near the bottom of the dial.

However having said that if any stat is stuck open the same thing would happen.

MadUsa1

yeah, I'm reading this off the OE dial.

Thing is, there's not much heat getting through the fans either, even if I turn the heater all the way to hot.

Reshard1977

iTrader: (17)

I had a similar problem with the fans not giving out hot air when I had a slow leak in my rad (which turned into a big leak!).

Are your coolant levels OK?

I'm no expert, but might be worth having a look at the rad.

I also read on here that you can test the termostat by putting in a bowl of warm water, and seeing if it opens and closes correctly.

MadUsa1

Coolant levels are fine and the whole coolant system has recently been pressure tested - came up all clear.

The thermostat is brand new, so I'm quite sure it's not broken.

No one else experienced this problem with a zerosports thermostat??

speedking

You could read the 'true' water temperature off the OBD socket, see if that gives any clues?

banny sti

iTrader: (68)

Do the heaters start cooling as the temp needle comes down?

53

iTrader: (41)

+1 when running mine ranges between 78-85 and can gets to 91 at stop after a hard run. I use a Scangauge to monitor temps on the go

Same temps on my classic monitoring with the Apexi Commander although it's never seen more than 88.

Myles

iTrader: (40)

On a standard therm, my bug runs at 85 when fully warm, going up to 94/95 before the fans kick in and it drops back to 85.

MadUsa1

What do you mean by the "true" water temperature? Is the oe gauge not accurate?

Banny: yes, the heaters cool down as the water temp drops.

banny sti

iTrader: (68)

The thermostat is defo sticking open then, as I had the same problem. I would not hammer the car till you get it sorted

MadUsa1

Really? how can you be so sure?

Can it be fixed or do I need a new one?

53

iTrader: (41)

You need a new one. Where did you buy it. There are reports of faulty ones, I know of 3-4 personally. I have them fitted to all three of my scoobs and never had a problem however.

MadUsa1

It was Scooby Projects that fitted it for me, about 2 months ago.

You never had problems with low water temperatures even when the ambient temperature was very low??

53

iTrader: (41)

Nope, been out today in the cold and although warm up takes a while, once up to temp makes little difference to the outside temp.

MadUsa1

what about on the motorway?

MadUsa1

Turns out the thermostat was broken, had a new zerosports 71°C one fitted and even with ambient temperatures as low as minus 15 it's holding the temperature steady.

It holds it slightly cooler than the OE (78°C) thermostat, as you would expect.

alcazar

iTrader: (2)

OK, first things first: a thermostat OPENS above a certain temperature. It is there to get the car warm quicker, as it allows the engine to heat small amounts of water at a time.

Fitting a thermostat that opens at a lower temperature leads to it OVER COOLING in low conditions. It's like running with NO thermostat. Try THAT and see if your heater works in winter

The idea is to get the engine up to running temperature as quickly as possible, since it is only when it is at tempearture that it is most economical.

Too far below= rich mixture, wasted fuel, maybe LESS performance.