Engine heat plummeting

Driving home the oter night in -3 degrees C, I watched the engine temperature drop quickly to the bottom of the dial (the engine hadn't got up to full temp in the 50 mile drive anyway). I was surprised to see it drop so quickly. Is this normal in cold temperatures? Is a radiator muff the answer or do I have a problem with the cooling system???

your thermostat might be gubbed and staying open, which allows too much cooling to take place..

i drove from here to paris(about 300miles) with a knacked thermo and me gauge barely shifted off cold..

That could explain it... is there a simple test to check for that??

best way is to take it out.. it should be closed and open up in hot water.. you can used a thermometer to check the temp it opens at but thats a waste of time as generally they work or don't work. if its stuck open you don't need to bother with the hot water as it will be obvious. get a noo one and noo gasket . shouldn't take yer more than 30 mins to do

Ok will do...Thanks for that!!!

Ed Foster said:

Ok will do...Thanks for that!!!

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what do you drive? the p38 V8's theromstats are in the bottom hose, yellowy coloured plastic ball with bottom hose either side of it AND smaller heater size hose's taking hot water to and from it so it knows when to open. as slob said see if it stuck open, blow through the bottom hose side and see!

Morning Ed

I have the same situation with mine the 2.5 BMW diesel

Initially i thought it was the a stuck open thermostat - probably still is Having looked at whats involved at getting at a thermostat on one of these morors i decided to leave it for a weekend

What i did notice with mine is that the viscus fan was blowing from start even when the moror was stone cold. (in my case) i did a test drive with the viscus fan stoped (stopped it with a thick rag) and noticed the motor warmed up much faster - in the end i decided for a different (safer short-term fix...

What i did to get the motor warming up sooner is to reduce the air flow to the radiator

This i did by inserting a piece of what is in effect lino with a 14-15 inch hole cut out in the middle to alow about a third of the air flow through

This was inserted behind the intercooler in front of the radiator. you can easilly get at this by removong the top body panel over the intercooler / radiator and removing the front plastic main grill 5 mins work.

Drove a route of about 3-4 mile from stone cold and the motor warms up and the temp gauge sits in the middle of the gauge at 12 o clock - this is driving around town and even out on the autobahn at 70-80MPH it maintains its position. - & of course if the motor is warming up sooner you economy is a heck os lot better - sooner...

NOTE: this is only a Short-term measure and when i get around to it i will fit a kenlowe electric fan & put a new thermostat in

hope the info helps

i tried that trick with cardboard on me way to paris and it had no affect. but then i only covered about half the rad. course different vehicle and different injuns will react differently. i even tried removing viscous fan but that had no effect

Haven't had a chance to check the thermostat yet but will try too in the next week or so. I did take my motor to see the mechanic yesterday he noticed that the coolant level had gone down since he serviced it a couple of weeks ago and said that I should keep an eye on it. He did warn about 4.6's and slipped liners etc but said you usually get a misfire on starting with that but so far it hasn't done that yet. What are the main symtons of slipped liners? I've done a couple of hundred miles since I noticed the initial problem and it is still running a bit cool but hasn't gone down to zero again....... yet.

as the guy said, misfire from moisture on plugs, will clear after a while, lots of condensation from exhaust, using water, and check your spark plugs, No's 4 and 6 on mine had rusty electrodes from dampness entering the cylinder, sometimes it may hydralic, water in cylinder stops it from turning over when starting when left for a while...............and yes, i have been through this too.....
it didnt over heat but used loads of water, it did over heat come the summer! new block and top hat liners, make shure you get top hat liners if this is what you need, they can never slip!
hope its not this though, its christmas!

Have now replaced the thermostat and the problem has been solved! Many thanks for everyones advice on this!