Re: '87 5kTQ ThermoSwitch

["A. G. R. Sutherland" <agrs@ohm.york.ac.uk>]

   Michael,
    I am confused by your references to thermostat and thermoswitch in the
  same sentence and apparently in close physical relation to each other.
   I have a 1984 4000 5cyc in which the thermostat is below the top radiator
  hose connection at the engine and goes of to the front bottom of the 
  radiator on the rear bottom of the radiator just along from the previous
  connection is the thermoswitch which controls the fan. I don't imagine that
  the 5000 is all that different.
   I have had troubles with my cooling system ever since I blew my cylinder
  head gasket. When I eventually got the car started after replacing it, 
  the damned thing overheated all the time because the fan refused to cut 
  in.
   Here just to worry you or hopefully give you some clues is my sad 
  chronicle of events.
   1) Top up coolant and oil levels before 50 mile round trip.
   2) Drive 20 miles car overheats.
   3) Discover I have not replaced pressure cap after 1)
   4) Screw the damned thing on and crawl to destination
   5) After 5 hours set off home, 10 mile on and car won't go no further
   6) Get towed 20 miles home
   7) Replace cylinder head gasket.
   8) Readjust valve timing.
   9) Readjust ignition timing
  10) Engine now running but constantly overheats
  11) Test thermostat in pan of boiling water and then cold It works
  12) Clean Thermoswitch contacts fan cuts in but only after overheating
  13) Change thermoswitch, no change
  14) Flush and reverse flush radiator no change
  15) Discover pinprick hole in top hose under jubilee clip, trim tophose
  16) Car now on road and occassionally overheats in slow traffic.
  17) Get fed up with 16), replace thermostat, everything fine.
  18) Drive 500 miles on holiday without any problem.
  19) Two weeks back at work and we are back to 16)
  20) Question What do I do now?
      B.T.W & F.Y.I the guy who sold me the new thermostat advised me to
    watch out for airlocks as according to him both the 4000 and 5000
    cooling systems are prone to it. I have found this to be the case
    and the airlock usually occurs on mine right at the bottom of the
    hose from the thermostat preventing the sensor on the thermoswitch
    from reading the true water temperature. Try pumping the hose by hand
    with the pressure cap off, it does help but the problem can reccur.
    Hope this helps, and hope someone can help me. 
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    Arthur G. R. Sutherland	      |
    Electronics Teaching Laboratories |	Tel. Work +44 (0)1904 432371
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	        	I am not always right
	        	and though I am seldom wrong
		        degrees of error are relative.

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