engine and drivetrain heating up when using engine to slow

[vintage_car]

After an extended drive, and nothing to aggressive, just normal back road driving...I noticed that if I let the engine slow itself going down hills, instead of the breaks that it began to run much hotter. I have never seen this before. It was nice weather, not hot or humid...70's. suggestions? Do these engine's not like that, and it is better to use brakes? just worry about brake fade.

[TobyB]

That doesn't make sense to me, either-

it should cool when you're off throttle... well, as long as you're not

keeping it at 6k in 2nd going downhill...

Ideally, the thermostat would keep everything

equal, but I usually notice it's a little cooler on the downhill

side of a mountain...

I'm wondering if maybe your gauge is wonky, or a ground

is a bit loose on the engine or alternator, and the physical

position of the motor has something to do with it???

huh.

t

[dharvey]

Hmm, mine seems to warm up slightly when useing engine compression to slow at lower speeds (-40). Then roll to a stop, as I accelerate away it cools back down when up to road speed.

From the stop sighn two blocks away, to the house and waiting to get into the garage it warms up noticably from the center of 3 oclock to the top of what would be 3. I do have a condensor in front of the radiator, so that probably accounts for some of it.

[vintage_car]

I agree, but it doesn;t I would say that it might be 3.5- maybe 4K rpms slowing it down- nothing to aggressive. The temp guage has to be working correctly as it will actually begin to cool back down under normal driving conditions on flatter terrain. It doesn't get overyly hot...probably up to about 200...but that is about 25 degrees hotter than it normally runs. extremely odd!

[Beaner7102]

Using the engine to slow you going down hills should actually drop the temp, as the engine is not under load, it is being helped along by gravity pulling your car down the mountain. That is unless you are in 2nd and its screaming at 5k rpm.

Check your oil and water levels. If they are low the engine will still be hot from the uphill drive and may not be 'normal' until you are onto the flats.

Also what plugs do you run, a hotter plug also makes the engine run hotter. Whats the timing like? too advanced and it will run hot too.

Just a few thoughts. Beaner7102

[m-racer]

First, I am no mechanical wiz, but could it be that you have a weak water pump? I have a modified E30 M3 that would heat up at stop lights, etc. and if you blipped the throttle it would cool back down. Turned out to be the water pump. I am sure someone who undestands the M10 waterpump will chime in and correct me if I am wrong. Just a thought.