temperature rising in traffic

[dominic]

Hi guys,

My temperate guage is creeping up in traffic with the heater on full, it's fine when driving at a constant speed, the is no housing round the fan blade from the radiator, i've been told this may be the problem.

aparantley the viscous coupling is ok.

Any suggestions?

[gerrit323]

Did you already check the ignition timing .. if she's set slightly too late then overheating at standstill will be the case also

The housing around the fan doesn't make a huge difference ..

Gerrit

[dominic]

thanks mate, i'll check it out

[e21-Mark]

Have you checked viscous coupling?

Turn on engine and try stopping the fan with a rolled up newspaper. DON'T use your fingers! When the engine is cold the blade should stop easily, but when hot it should keep spinning and knock the newspaper out of the way. Personally, I would say it's more likely to be the coupling than a missing shroud. Also check coolant level and fan belt tension.

[Jeroen]

That was my first guess as well but I believe his car is a 316 which does not have the viscous coupling. Calls for a little bit more info on when the problem started and if any work was done just before that point. Could be ignition, lack of flow due to an air pocket or failing water pump or thermostat. Is there any consumption of coolant? You may loose it due to a defective rad cap, and this lack of pressure also pushes coolant temp up. White smoke from the exhaust when warm? Idle or cold start issues? Did you happen to have a look at the spark plugs recently?

Edit: what am I doing, find more info in the FAQ section of this forum

[Reck]

Another M10 overheating?! Glad I'm not the only one.. How much is it overheating by? Where does the needle sit at idle and when driving?

Overheat at idle suggests bad ignition and or a rad/water pump not doing their job properly, or worst case a head gasket fail. Rad could be clogged or water pump impellers corroded, meaning inadequate cooling when air is not moving across the rad or water not circulating fast enough (as it is when driving).

I've had three M10's that do it now so my troubleshooting normally goes in this sort of order;

- Get it tuned (valve clearances, timing, carb etc.)

- Check grounding on instrument control panel and wiring at the temp sensor.

- Tighten as many coolant pipe clips as you can find. Replace any obviously corroded examples. Ditto for replacing any damaged or old rubber pipes (squeeze them, if they feel 'crunchy' they probably need replacing). Small leaks are possible, I found one on the heater exit to rad pipe.

- Flush coolant system, refill and bleed.

- Replace rad cap, thermostat, waterpump, rad (in that order - cheapest to most expensive).

- If you're still over heating at this point, it could be head gasket related. Get a hydrocarbon test done, check for 'foam' under the oil cap, look for white smoke at the exhaust once warm or look out for coolant loss (I guess you can lose a very small amount normally as there is no catchment for coolant expelled by the rad, but if you're topping it up regularly this can indicate something wrong).

[e21-Mark]

I read viscous coupling and assumed was 320/323.

I'd flush the rad and fit a new water pump and thermostat. The impeller can break down with age and pump less water around. A new one can work wonders and they're not too expensive. Assuming the head gasket is OK obviously.

[dominic]

I was in traffic for an hour and a half in london the other evening, the temperature rose to about 3 quarters but didn't overheat,

there is no obvious signs of head gasket problems, no white smoke, no milky residue round the oil cap no water exiting from the exhaust and no loss of coolant, would the type of coolant have anything to do with it?

I'll flush the coolant and replace with the correct stuff and see where we go, it's never happened as i've never been in bad traffic before, if it's for like 10 minutes then it rises to just over half way but I must have been going under 5 miles an hour for almost 2 hours.

cheers for your advice guys, i'll look into it when i've got some light and see where i get.

[e21-Mark]

Sounds perfectly normal to me.

[Jeroen]

Agree, that's not too bad for a traffic jam, pls keep in mind that between halfway and three quarters on the gauge the temp difference is only abt 8-10 degrees

[dominic]

Cool, that's put my mind at rest then!!

cheers!

[Reck]

Is that right though? If the cooling system was functioning properly, shouldn't the temp needle always sit on, or very close to, the centre mark as a result of the thermostat opening and closing? I thought if there was any deviation of more than say one or two needle widths (except when carrying a large load - i.e. a trailer up a hill) then that indicates that something, somewhere isn't working quite as it should...