Conference terri::cars_uk

  Expansion tanks are only there for when cars run hotter than they should. 
  As the water pressure increases the radiator releases the excess pressure
  and the water flows into the expansion tank and as the engine cools down 
  the water is sucked back in. If there is no expansion tank then the water 
  will just fall on the floor and it may be necessary to top up the water
  more often if the engine runs too hot a lot. The lack of expansion tank
  only really makes it harder to check your coolant level.
	

    Thanks,
    
    Try telling my wife that!
    
    Tim

    
    	Can anyone help me with my hot and bothered problem.When my car
    gets to just above operating temperature(after a motorway drive)and 
    I get off the motorway and stop,the idling speed is slightly high.The
    slightly high idling speed (normally 850rmp and when warm is
    950-1000rmp)causes the car to have pre-ignition.I'm now running my car
    on 4Star and this pre-ignition problem happens less frequently than
    with unleaded.Should I adjust my basic idling speed?,my mixture?
    
    	Any hints?????
    			Much appreiciated!
    Happy Easter.
    					Andy...
    

    Andy, my RS Turbo's idle speed rises from 950 approx to 1100rpm after a
    motorway drive, but it drops back down again after a couple of mins.
    There is no sign of pre-ignition though. I run the RS on leaded though.
    Have you had the engine converted to unleaded, or is it already
    supposed to be capable of running on it without adjustment.
    
    I'm not going to touch my RS, because a fellow I know had his XR3i
    converted and the "flaming" engine went on fire (no pun intended:-).
    
    Gary.

    	
    Gary,
    	When you say after a couple of mins,do you mean that when you stop
    you leave your car to run for a short while?I know you're supposed to do
    this with some turbos anyway.If I leave the car to stand the revs do
    drop slightly,should I leave to stand for a bit longer????
    			
    		Thanks for the reply.
    	Andy-I-suppose-Ford-drivers-aren't-that-bad.
           
    			       

	Andy,

	Is the car injection or carb?
	Fixed electronic or mapped ignition...?

	_Richard

    
    	Richard,
    		It's an Astra SR.It's got a Varajet II carburetter.
    	I'm pretty sure it's fixed electronic ignition.
    	When I adjusted my idling speed,I started the car and left it to
    run for a while,then I adjusted it.Should give it a run out and then
    adjust it?
    			Andy....??.....
    

	Andy,

	Your idle speed will depend on numerous factors :-
	Timing, mixture, air density/temp etc..., water temp etc...

	The engine should be warm,  however I have never considered it 
	necessary to go for a run beforehand...

	On mine the ignition is mapped according to inlet vacuum, oil temp,
	underbonnet temp and is selected from a number of possible curves.
	The system has an air-bypass valve to correct idle speed when air
	con or power steering is operated,  and even so,  I too get the 
	increase and decrease in idle speed.

	I was also suffering from pre-ignition when setting off after long 
	periods of idling,  I found no satisfactory cure for this until I
	flushed out the whole cooling system,  this has made the whole system
	run somewhat cooler and prevent the problem....

	As to your car,  I think it is probably a combination of engine
	design and lousy petrol,  I just read an article about fuels (Which?)
	this confirmed the difference between different petrols and rated
	Esso,Bp,Shell as expensive but better as they contain detergent.
	If this is combined with the fact we now have much lower octane
	fuel compared to 10years ago, ie Super+ unleaded is higher octane
	then 4*...!,  then pre-ignition is to be expected I guess...

	Still I woffle on...

	High mileage engine... perhaps decoke..?
	Does it run hot...?
	Have you checked timing with strobe recently...?

	_Richard

    
    	Richard,
    		I've noticed that the car has a tendancy to suffer from
    pre-ignition when it's hot.Do you think I should try draining the
    cooling system?Is it easy to do??
    
    			Cheers,
    					Andy....(What do you drive?)
    

	Andy,

	It would be a good idea to reverse flush the cooling system and
	heater matrix for any car over 2 years or so,  it seems to be
	less important on 'hi-tech' all alloy machines as with good 
	coolant and de-ionized water etc...,  no problems seem to occur.

	Given the fact that you have one of the General's 'family two'
	engines that has plenty of iron in it,  it will probably be quite 
	full of sludge after a couple of years.  A complete reverse
	flush with a hosepipe will hopefully clear things,  (don't forget
	the heater matrix though, as these are factored into the cooling
	requirements of most modern cars).

	As for how to do the job,  the Haynes is usually best for simple
	jobs like this....

	_Richard

    
    	Richard,
    
    	>>Reverse flush!
    
    	Is this done by attaching a hose to the LHS of my radiator(after
    removing the hose)and turning the tap on?
    
    
    	>>Heater matrix
    	
    	??
    
    		Thanks for the advice!
    
    
    			Eternally in you debt
    		Andy.....(What do you drive?)
    

Hi Andy,

I had an identical problem to yourself.  Except only after 
sitting in a traffic queue for 20 minutes.  Idling would 
get a little keen and pinking could be heard, even though 
the Oil and Water Tempratures read as normal.

While reverse flushing the cooling system, I checked the 
Water Thermostat.  A little golf ball sized valve at the 
bottom radiator water inlet, this should open at about 100 
centigrade, to make use of the rad.  They are only about 
5 pounds a throw.  Dead easy to change while you have the 
bottom hose off.

Drop it in a kettle to test it.  Mine opened, but with not 
enough of a gap and too late.  Hence a hot and bad 
tempered Golf GTI.

Robert.

Andy,

Re. .12 I agree most wholeheartedly....

As for reverse flush,  drop off both the top and bottom hoses from the radiator,
Placehosepipe in bottom hose and blast through....!

>> Heater Matrix..?

The thing that keeps your toes warm in the winter.....

Seriously though,  you will find two small'ish hoses going through the bulkhead
into the main body of the car,  these need to be disconnected and flushed 
through both ways until no more dirty water,silt comes out...

Don't forget to use decent antifreeze when refilling (at least 33%).

If this doesn't cure the original problem,  it will probably mean your cooling
system will be in much better shape for the summer.

_Richard

BTW: I drive Vauxhall Senators (3.0iCD and 3.0i Police Special)

    RE.8
    
    	Hi Richard,
    		This morning I went to a BP garage instead of my usual
    Texaco,I drove to work on the M4,(as usual)then when I got to Winnersh
    Triangle and turned my car off i had no pre-ignition.I usually have to
    let the car stand for a few seconds for the idling speed to drop,but it
    dropped almost instantly.I think that the fault had been lousy fuel as
    you had suggested.
    
    		I'm getting it Krypton tuned tonight so i'll see what
    happens after that.
    
    		Cheers,
    	Andy..

    
    	(Some months later!)   RE-1
    
    	Well no pre-ignition,but! 
    		the car is running quite hot.I put it in to my Vauxhall
    dealer and while they were doing a few jobs that needed doing I asked
    if they would flush and replenish my cooling system,which they did.
    		But the car still runs at just under the three-quarter
    mark.I put Redex through the Carboretter no cure,but the only thing
    that came out of this experience is that three days later I put a tank
    of Mobil 1 petrol in it and it ran at a low temp.Then not thinking I
    had to fill it up and used BP.The car ran hot again.
    
    	Can petrol really make this much difference?
    	
    	Andy.