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RE: Temp sensor position

To: "Barrie Robinson" <>
Subject: RE: Temp sensor position
From: "Dodd, Kelvin" <>
Date: Fri, 29 Dec 2006 16:42:00 -0800

What the others have said. Once the thermostat opens, the engine
temperature should stabilize at a reasonable operating temperature,
somewhere below the 190-200 degree range. Under normal conditions, air
flow through the radiator allows adequate cooling under all loading.
When stationary, or at low speed the radiator will not reject enough
heat without supplemental air flow, so the cooling fan should be
switched by a radiator mounted temp sender.

When the engine is shut off, there will be some heat soak as the water
pump will no longer move fluid through the engine block and radiator,
but this is normal and since there are no BTU producing explosions the
engine will be cooling down.

First off, is your car overheating when it is being driven at freeway
speeds, or just when in stop and go traffic.

If at freeway speeds, take a good look at airflow through the radiator
path and make sure that there are no places where the flow is getting
defeated. Sometimes building a shelf between the bottom of the radiator
and the front of the engine can make a big difference, especially if you
have done too good of a job sealing up the inner fenders where the
headers go through.

If the airflow is good, then there is something wrong with the engine
such as timing or air locks.

If the car is overheating in stop and go situations when the cooling fan
is running, then I'd suggest changing the electric cooling fan or
fabricating a shroud for it.

I did take a moment to check out your British V8 blurb and noted the
image of the engine compartment showing the cooling fan setup. If you
still have this design, I'd be taking a hard look at the efficiency of
the cooling fan. From what I could see in the image, there is a good
distance between the blades and the core due to the top tank sticking
out. You might be better off with a smaller diameter shrouded fan
attached as close to the core as possible. The current design looks to
my un-educated eye as if it may just be stirring the fug behind the
radiator and not doing a creditable job of pulling through it.

I am officially in the Glen Towery camp. The factory twin fan set up
pushes a lot of air with two small fans. An interesting tit bit for
those using the stock twin fan system would be to take a look at how the
TR8 cooling fan system is switched, as it uses a two stage system
operating two fans individually at low and high speed.

Hoping this helps with your overheating problems


Barrie Robinson wrote:

> Folks at world,
> Having had some fun with the over-heating in my MGB GT V8 I have sort
> of worried around all the aspects thus learning a great deal from our
> gurus (for which many thanks).  There are still some facets that
> require some scientific confirmation but one little item comes to the
> top of my greying grey matter......  My temp sensor is on the radiator

> and this controls the electric fan.   Thus when the rad is cooled
> while the car is stationary, off goes the fan despite the fact that
> the engine block may be still stonking hot!   There is practically no
> heat path between them when the pump has stopped swirling water.
> Would it not be better therefore to put the sensor on the block, or at

> least the intake manifold?
> Regards
> Barrie
> Barrie Robinson
> (705) 721-9060
> Your messages not reaching the list?

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