overheating confused

2003 mg tf 1.8 i was driving home with the blower in car on hot , suddenly it was blowing cold an temp gauge going up so i stopped to check it out, the front rad was cold too but no water loss, i let it cool down an limpped it home kept stopping to cool it down , then blower started getting warm an temp dropped !!! now its cold again an temp up any ideas pls am changing thermostat as i type this

:welcome: and try bleeding any trapped air out in the first instance. Click here for the guide. :yesnod:

Thermostat (PRT) Pressure Relief - Replacement guide.
Thermostat replacement guide - Replacement guide.
Thermostat replacement pre 2002. - Thermostat replacement, older type, pre 2002.

Let us know how you get on with your stat change. :broon:

First of all



A cold heater normally indicates an airlock in the cooling system.
As a first step I'd refill and bleed the cooling system, you find a great how-to here.

Could be caused by a leak where you loose coolant, also a blocked jiggle valve in the inlet manifold may cause it.

Try bleeding first, it may solve the issue.

thanks for the replys am old school thats why i thought the thermostat , i took it apart to find there it was missing and after reading on here its got one near the coolent pipes , now thinking air lock as 2 weaks ago i replaced the coolent pipes and bled the system only once while engine was not running . i got it mot an taxed it then got the overheating problem after changing the pipes lol now am strugling to get the 10 mm bolts back in the pipe mounts going to the original thermostat , wish i just bled it again now , my other car is air coold so never had this problem its a nova sterling from 1970 if you no them , anyway ill let you no how i get on with the bleeding an hope its back on the road shortly

got it all back together and folled an bled system , its now blowing hot air again in car so fingers crossed , gonna run it round streets then let it cool an bleed it again , thanks for the help

if you have a chance raise the rear of the car (ramps) and leave the expansion tank cap open over night.
Then bleed again.

will try that tonight thanks again for all the help