thermostats

[JJC]

Hello all : Anybody ever conduct a back to back test....no thermostats vs. thermostats ? Wonder if you might share results. Thank you.

JJC

[Kalle Borg]

If you do not have thermostats monted, the bypass will constantly be open. This will result in that you will have only maybe 50% cooling capacity as half of the cooling liquid will flow through the bypass instead of through the radiator. You can see the bypass port in the bottom of the thermostate housing. The bypass will allow water to circulate through the engine when the engine is warming up. As the thermostates opens, the bypass will be blocked of. It is vital that you use the right type of thermostates with twoo discs - one to regulate the main flow and one to block the bypass. On six cylinder E-types the bypass is blocked by a sleeve on the thermostate. Using incorrect thermostate is, I think, the no one reason to overheating Jaguars.

[mgcjag]

And dont forget on the S3 there are 2 stats

[MarekH]

The only people who consider removing thermostats are racers:- they run at only tightly constrained rpm, with constant high airflow and the result is that the engine settles at a particular tempaerature and that's that. They then fine tune what that temperature will be by constraining either the airflow or the waterflow with the aim of minimising any speed loss due to unnecessary airflow which doesn't generate downforce. They also often get it wrong and their sponsors have to stump up a lot of money for their incompetence.

For a road car user, the back to back test usually manifests itself by a sharing of the results in the form of a post which contains the words:- "my cooling system isn't working" or "I'm overheating" or "it takes too long to get up to temperature".

You can see what effect a thermostat has on water temperature by looking at the blue line in the middle graph. The car is idling on the driveway - rpm, water flow and airflow are constant, but the engine temperature initially rises at a rapid rate and then remains constrained between the thermostat ratred temperature and ~6'c above that.



Note that the first dip in the temperature is greater than the others. This is because the water in the radiator is stone cold rather than that which has previously been around through the engine.

Also note that once the car is going somewhere, the water temperature moves about even less and is not well correlated with supply and demand, but still remains at just over its minimum design temperature. This is because it takes time for any change in water flow to take effect.

If you want to know more then search either this site or jag-lovers.com with the parameters "thermostat marek".

kind regards
Marek

[Tbob]

.. On six cylinder E-types the bypass is blocked by a sleeve on the thermostate.

Is this true for sixes with the secondary intake manifold? US 69-71 car. I don't see such a sleeve on this thermostat. Is this the correct one?

[mgcjag]

Hi Bob.....some use the sleeve type.....a 69-71 car will use the type you show

[Kalle Borg]

You are right! Thermostates with sleeve goes on Series 1. Series 2 have the type shown on your photo. Sorry about that....