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07/05/2004 13:24:10   toby   during recent trips out noticed temp gauge reading well below half.i replaced expansion bottle cap as this was not holding pressure.i have replaced the thermostat and faulty temp sender unit (end fell off).gauge now reads well over way problem gets worse when going down hill,free wheel engaged ,engine on idle,gauge goes into the red then falls back,i have made sure the cooling system is bleed (through heater valve)and the water level is ok.two things that i think of that can be wrong
1.wrong temperature thermostate fitted what should it be!
2.whater pump impeller problem
can anydody help,
 
07/05/2004 13:24:46   toby   during recent trips out noticed temp gauge reading well below half.i replaced expansion bottle cap as this was not holding pressure.i have replaced the thermostat and faulty temp sender unit (end fell off).gauge now reads well over way problem gets worse when going down hill,free wheel engaged ,engine on idle,gauge goes into the red then falls back,i have made sure the cooling system is bleed (through heater valve)and the water level is ok.two things that i think of that can be wrong
1.wrong temperature thermostate fitted what should it be!
2.whater pump impeller problem
can anydody help,
 
08/05/2004 11:25:09   Senor Burt   Sounds like the thermostat not opening soon enough. Haynes manual only lists one type opening at 83 degrees. Could just be faulty.
If a problem starts after you have replaced parts, suspect those parts!  
10/05/2004 09:32:03   Steve   I'm working through a similar problem with my car at the moment. It started overheating after I fitted a new heater valve but the problem was chased to the thermostat which started openeing at hotter and hotter temperatures until the car was undrivable.
I got a new thermostat from a local shop and they said it was the same as a Vauxhall part. However I fitted this part and the car overheated. I have now ordered a replacement from Highate which opens at 82 degrees. The Vauxhall thermostat had 92 stamped on it !
In the meantime I am running with no thermostat which makes the car run cold but at least it's drivable. You could also remove the thermostat and see if it alters the running temperature. Also check the number stamped on your new thermostat.  
10/05/2004 10:17:40   Senor Burt   Steve - where did you get the new heater valve?  
10/05/2004 16:07:12   Alistair   Toby - this sounds like you're cooling system is either short of water and needs bleading or it's partly blocked and needs a recore. - have you bled all the air out via the bleed valve on the side of the heater box? You need to do it cold, then let it warm up & keep doing it, lettin it settle, doing it again until no more air comes out.

What's happening is that if the rad is (part-)full of air, it only gets enough water through to cool it properly when the pump is working a bit harder (ie higher revs) - at tickover (freewheeling) there's not enough pump pressure to get the water through the rad so it quickly gets hot. The same can happen when your rad is a bit blocked, or the 'stat isn't opening fully.

Suggest you try re-bleading the system first, if that doesn't cure then try removing the 'stat, and/or flushing the rad out. If still no success get a new core in the rad.
 
10/05/2004 16:50:20   Richard   Bleed the heater with the engine on tickover and the heater switched to hot. If no luck do as above and remove the thermostat and eliminate it as a cause. Failing this have you got the correct sender, try one of those cheap garden centre temp probs in the radiator top hose. Fit it down the hose and reclamp the hose up with the clip. Run the engine and see what temp the water is at.  
13/05/2004 07:42:29   Richard   Car looks good in Practical Classics. A plus is that the Saab 96 range is voted in the top 40. Notice how high the Skoda is though!?  
14/05/2004 10:21:54   simon   Dear Richard,
I thought that you made a commitment towards containing your enthusiasms for other marques in this forum!?! ;-)  


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