Club 80-90 Forums

Hi, Can any one tell me if there should be heat shields on my water cooled 2.1petrol. I've Bled it. Run it with out the middle of the thermostat. I"m still not happy with how hot it gets. It's runs in the middle of the red light and white line, just before the little white dot. It doesn't seam to drop even when the fan kicks in, only when i turn the heater on hot and No3 for the fan. Cheers

Russnthebus wrote:It doesn't seam to drop even when the fan kicks in, only when i turn the heater on hot and No3 for the fan. Cheers

The last statement seems to be quite revealing and infers that whilst increased air flow over the heater matrix has a positive effect, the more powerful radiator fan does not.
The only conclusion you can draw from this is an ineffective radiator, either blocked or it has a massive air lock. Either way...it isn't taking away heat from the coolant 'as it should'.
As for the 'tinware' question...yes they have shields over the pushrod tubes and exhaust silencer but nothing that is going to prevent cooling.

Martin

I think a little recap of the basics of cooling might be a good plan here...

Air-cooled engines are cooled by the air flowing over the engine itself. The head and barrels are finned to aid cooling, and the correct flow of air is essential. The tinware is vital to keep it flowing in the right places, for the cool air to reach the hot bits, and the hot air to reach the outside world.

Water-cooled engines are cooled by the water flowing over the engine itself. The hot water's then taken to the radiator, where air passing over it takes the heat away, before the water's returned to the engine. One of the advantages of water cooling is better control of the engine temperature. Hot enough for efficient engine operation, not so hot that the coolant boils. Airflow over the engine itself makes a difference in a front engined vehicle, but primarily because that's air that's come through the rad. With the rad and engine at opposite ends, the airflow over the engine's more-or-less irrelevant.

That "normal" band of temperature is what the engine's designed to operate within. The lower end of that band is controlled by the thermostat - if the coolant's not hot enough, it's prevented from losing heat, by stopping it flowing to the rad. If it's too hot, the fan kicks in to increase airflow over the rad. There's only a handful of degrees between the top and bottom of that range - roughly 85-95deg. Remember, it's pressurised and not running plain water, so it won't boil until about 115deg. Obviously, that all requires the cooling system to be in good condition. If the rad's partially blocked, then the fan might not ever kick in, because the hot water can't get to the switch. Or the fan might kick in, but it still can't dissipate the heat, because there's not enough air flowing over the restricted area of the rad that's actually doing something.

Taking the thermostat out will never do ANYTHING to control overheating, because once the coolant's up to that lower end of "normal", the 'stat is open anyway. Actually, "never" isn't quite right. If the 'stat is permanently closed, it'd boil over within minutes just idling, because no heat will ever get to the rad. Removing the 'stat would cure that. But that's the only situation. Otherwise, taking the 'stat out will just prevent or delay the engine getting to normal efficient temperature.

Turning the heater and fan on full just gives you a small extra radiator and extra airflow, on the engine side of the 'stat.

So... If the coolant's not overheating and splurging everywhere, the rad gets hot evenly, the fan comes in and out when you're stuck in traffic or at the top of a long steep hill, and the temp gauge doesn't drop below "normal" (but might a bit when you blat the heating on full)... it sounds like everything's working about right.

Don't get TOO hung up on the exact positon of the temp gauge needle - it depends on the exact resistances the sender puts out, the condition of the wiring between the sender and gauge, and the exact calibration of the gauge as to how much movement for what resistances - just accept where your van's "normal" is. Once, of course, you've made sure your cooling system really is healthy.

Easiest and most basic check is to take the front grilles off, cold start the van, watch the needle, and as it gets towards "normal", make sure the rad gets warm all over just with your hand. Once the 'stat opens, you'll feel the hot flowing in and around the rad. When it's fully up to normal, remember that the rad contains 80+deg water, so it WILL be hot to the touch.

Thanks for your help every one