Thread: Is running a td5 without a thermostat really such a bad idea?

A HUGE no-no!!!!
Will overheat for sure when it works hard.
Andrew

Were you running the correct mix of coolant? As you probably know, the gauge should show when it gets insanely hot. I'd be questioning why it wasn't. Actually, also have a look at the pressure valve/cap - this has the biggest impact on the coolants boiling point.

BTW, I'm guessing the same effects as you have WRT the thermo not being in.

Originally Posted by LandyAndy

A HUGE no-no!!!!
Will overheat for sure when it works hard.
Andrew

Why would it overheat? The thermo opens fully at about 90 degrees anyway and they run up to about 110 when hot.

It gets up to about 80degrees max when worked hard, I checked this with the nano, so highly doubt it will ever overheat without the thermostat. The coolant travels through the radiator so heat is lost the whole time. The coolant mixture was a little lean on coolant, so now I am running the correct mixture. I think I will replace the thermo.....I bought a new genuine one anyway so may as well use it.

btw don't trust non genuine thermostats, they don't last long at all.

Originally Posted by Slunnie

Why would it overheat? The thermo opens fully at about 90 degrees anyway and they run up to about 110 when hot.

The thermostat also provides some restriction to the flow of coolant, even when fully opened.
Without the thermostat, coolant can flow through the radiator too quickly to allow heat to be removed from the coolant. As a result, heat continues to build.

The thermostat in the Td5 also causes the coolant circuit to change as it warms up due to a one way valve in one of the branches. There is a hose that acts as a radiator bypass when cold. When warm, the valve closes (due to the flow created from by the open thermostat) and the flow in this hose reverses due to a small hole in the one-way valve.

I certainly wouldn't run without the thermostat in.

a word of warning check the NEW thermostat is working before fitting.
i have bought 2 new ones and they where duds

Running any vehicle designed for a thermostat without one is usually a bad idea for two reasons.

The obvious one is that it means that the engine will almost certainly warm up much more slowly and run at a lower than designed temperature. This will cause more rapid wear (sometimes much more rapid) and require more frequent oil changes, as teh oil does not get hot enough to evaporate condensation. Depends on driving and weather conditions.

Less obvious is that removal of the thermostat changes the pressure distribution in the cooling system. This may not be a problem, but with modern engines it is more likely to be, as the pressure distribution affects the route and speed of the that coolant through the head and block due to changes from laminar to turbulent flow. This can lead to localised over and under cooling, and consequent distortion or even cracking of the metal, particularly a problem with alloy heads, which is why I would worry about it a lot more with the Td5 than, say, a Series engine. There may not be that high a risk, but the cost of faults (which may appear years later) could be very high.

I would consider it as a solution of last resort in an outback emergency!

John

Originally Posted by awabbit6

The thermostat also provides some restriction to the flow of coolant, even when fully opened.
Without the thermostat, coolant can flow through the radiator too quickly to allow heat to be removed from the coolant. As a result, heat continues to build.

This is an urban legend. You cannot push water through a radiator too fast for it to cool. It's a circuit and the faster you move the water, the greater the turbulence and more heat is moved as a result.
The faster you move water in a cooling circuit the more even the temperature becomes in that circuit. But the heat energy transferred goes up, not down.

Thermostats are a necessary part of the cooling system. An electronically controlled engine like the TD5 will base injection timing and injection volumes off coolant temperature.