Problem With Overdrive

[paul 666]

hi all hope some one can help, i got a 1990 gt had it about a month and been trying to work out why the o/d drops..... the engine warms and i turn o/d on but after about 10 15 mins the temp needle drops right down to the point of dropping of the dash and o/d drops out so now im stopping all time as this works. i pull over put into park and after 3 mins or so the temp needle rises and so do o/d... plz someone help , been told possible thermostat ? or is there something else it could be.....thanks in advance if any one can help..

[GT4 BOOSTER]

i'd go with the thermostat as the symtoms are that of a failed thermostat . try blocking the air flow over the radiator with card board and try it , before taking it apart . the thermostats are prone to failure , usually a pin fails which keeps the spring in place.

[paul 666]

ok ill go with that . ill have a go at it today..thank you