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Zetec thermostat - drill a hole
Jonte - 11/5/11 at 05:44 AM

A few years ago when I was doing my cooling system on my zetec silvertop I read some threads where it was recommended to drill a hole in the thermostat.
I canīt find any of these threads and I donīt remember the benefit of that procedure. Think it was a 3-4mm hole drilled through the plate of the thermostat.

Anyone that can confirm this or advice against this?

austin man - 11/5/11 at 06:38 AM

I believe iits to aid cooling on number 4 cylinder as this one tends to get hotter and run weaker

britishtrident - 11/5/11 at 06:54 AM

It lets the thermostat open more quickly and aids bleeding air out when refilling, 2 x 3mm holes is about right.

coozer - 11/5/11 at 08:46 AM

Better just to plumb the system up correctly... it used to be to overcome the shortcomings of the raceline rail that moved the thermostat too far away form the engine.

contaminated - 11/5/11 at 09:50 AM

quote:
Originally posted by coozer
Better just to plumb the system up correctly... it used to be to overcome the shortcomings of the raceline rail that moved the thermostat too far away form the engine.


Exactly that. Only of benefit if you use the Raceline rail like me really. If you use the rail and don't run a header tank or heater etc there is no bypass to the thermostat. A bypass of some kind is required to let water circulate during the warm up phase until the thermostat opens. Two ways of doing it are:

1. Drill a 5mm hole in the outer ring of the thermostat
2. Remove the inner part of the thermostat altogether

I use Option 2 above - which gives me a nice free flow of coolant, but just enough restriction during the warm up phase.

Dan

02GF74 - 11/5/11 at 10:17 AM

quote:
Originally posted by contaminated
2. Remove the inner part of the thermostat altogether

I use Option 2 above - which gives me a nice free flow of coolant, but just enough restriction during the warm up phase.



then surely it no longer is a thermostat but a restirctor?

I am a paid up member of the small hole in 'stat fan club but last thermostat, one for crossflow was made of hardened steels so had t use diamond bits to grind the hole.

Also whenever fitting a new thermostat, alsways test it first !! (would have save me hundrends in a rebuild!!! )

contaminated - 11/5/11 at 11:23 AM

quote:
Originally posted by 02GF74
quote:
Originally posted by contaminated
2. Remove the inner part of the thermostat altogether

I use Option 2 above - which gives me a nice free flow of coolant, but just enough restriction during the warm up phase.



then surely it no longer is a thermostat but a restirctor?



Yup

mikemph - 11/5/11 at 12:10 PM

The hole in the stat has one other advantage if the stat fails at least you still get a bit of flow around the block maybe enough to nurse it home very carefully with heater turned on. I do this to any engine that will be used hard.

Jonte - 12/5/11 at 10:28 AM

Thanks for all replies
It looks lika Iīm gonna drill a hole tomorrow before I put everything together

DRC INDY 7 - 12/5/11 at 11:26 AM

I have 6 little holes in mine And when we had a mgb racecar we fitting restrictor plate with holes in from Cambridge motor sport