air lock or water pump

[tingle46]

hi all first time on the forum not sure if im doing this right as i tried last night and this morning it said error so will try again

i have a v8 3.9i 1998 discovery 1

when i bought it it had no thermostat so i put one in

i have tried to bleed the system with the front end as high as i can get it the problem is the heater only gets tepid and then goes cold the temp gauge stays on a 1/4 but will occasionally go to 3/4 and then drop back down there is no bubbles in the expansion tank and no smoke and runs like a dream

i tried getting air out of the heater pipes and found the return pipe has no flow unless you rev the engine could this be the water pump ? i also get a baning noise from behind the radio from time to time.

help any ideas!

[teabag]

You may have air in the system that's not normally a problem with the later V8s. So drain the cooling system and refill very slowly via the cap on top of the rad, when fill replace the cap 1/2 fill expansion tank turn the heater controls to hotand start and when it gets hot it wiil take coolent from the tank if required. Replace the cap and let cool, topup again to half way if required.

[fozsug]

Did you fit the thermostat with the jiggle pin at the top?

I would thoroughly flush the whole system and radiator, back flush as well

[tingle46]

thanks for the replys guys will try both options i also bought a new water pump anyway it cant do any harm

once again thanks