I test drove a '99 DII today that had coolant sitting on the top of the driver side valve cover. I did not see any coolant coming out but it appeared that it had come from a rubber hose that ran into the intake throttle body. Why would coolant be there? very odd.

 

Sounds like you solved the problem!

I believe there's a gasket on the throttle body that needs replacing. And yes, the throttle body does get coolant.

 

The above is true. It's the throttle body heater. Coolant flows through to heat the TB in conditions of extreme cold.

 

It could be as simple as tightening the hose clamps too. Pretty common problem, I believe you can just bypass it if you want.

 

yeah, just talked to a friend with a range rover and they blocked theirs off. I had no idea LRs had this feature, seems useless in warm climates.

 

Its not just LR's that have this, all cars do. Remember when you had a car with a carburator? Remember that little foil tube that went from the exhaust manifold to the aircleaner housing that sat ontop of the carb? That was your air intake heater. It directed warm air to the carb to keep it from icing up. It wasnt very efficient.
When they went to fuel injection they had to do something else since the airfilter was not ontop of the engine anymore and dirt could get around the heater tube.
So they use coolant lines. When your engine is running hot coolant warms the t-body to prevent icing.
When you are driving in the cold and the air is mositure laden you are sucking that cold water laden air into the engine and it will iceup on the t-body and restrict air flow. Just like if you were to stick your head out the window your face would ice up.
If you were stopped in traffic the heat under the hood would build up and melt it, but going down thehighway there is little to no heat under the hood.
Now as to why all cars have this, even in Arizona. The car manufactures have no idea where their car is going to be sold/driven/end up in its life. It might start in Texas and end up in Alaska.
If you live someplace warm you can bypass the t-body heater, it is a $5 part and a 30 min fix, it is your car so you can do whatever you want. If you want to set your trk on fire you can, if you want to fix your t-body heater you can do that too.

 

I've worked on lots of different vehicles before (mostly fuel injected) and I have never seen this feature before. I just took a look at my E46 BMW to verify it does not have it. It seems to me in warm climates this feature would heat the intake air giving you a hotter, less dense charge thus less power. Think intercooler in reverse.

 

I've often thought the same thing- kind of an anti-CAI but figured, hell, I'm not going anywhere fast anyway so might as well leave it.

 

On most newercars the coolant that circulates around the throttle body comes through the upper intake manifold, there are no hoses, the coolant flowsstraight from the block tothe upper intake manifold into the throttle body.This is probably why you havn't seen it.

 

I was just thinking about this yesterday, it's called a Fast Idle Air Valve onthe Mitsubishi Eclipse I just bought. I seems to work like a thermostat for the air intake:

"The function of the FIAV is to increase the idle speed anywhere from 801RPM to 1500RPM when the engine is cold. It does this by using coolant from the engine to heat a wax ball that is attached to a valve. When the coolant is cold the valve is open allowing air to bypass the throttle body which increases the idle RPM anywhere from 801RPM to approximately 1500RPM. When the coolant warms up the wax the valve is closed and the idle returns to its normal speed."

The previous owner blocked mine off and I can't get it to idle right. I was wondering if that is how it worked on a LR too, I'm guessing not since people seem to be able to bypass it without problems.