just re filling system on my 1995 4.0 p38.

i have read many threads on this but none seem to give a straight answer.

so my header tank is half full so almost at cold level. the heating is working well, but the radiator is not getting hot. i don't think the top rad pipe has any water in either. the fluid in the header tank is getting very hot, after about five/ten mins idling.

also - can you rely on the temp gauge to tell you if shes going to overheat? i.e. is it worth taking it for a run and seeing if it clears air itself?

Is the radiator cool all over or just in certain areas?

Perhaps pull your thermostat and drop it in a pan of boiling water and see if it pops open. It may be stuck.

yep will give that a try. cheers, radiator seems to be cool all over.

Wax stats always fail shut, they never fail open. What does your temp gauge say? When the temp gauge reaches normal temp the rad should be at least warm. 10 mins idling may not be enough to reach stat opening temp.

ok well, the temp gauge comes up to the middle (directly pointing up) and stays there the bottom of the rad is still cold to touch at this stage, the header tank is not far off boiling and the heater is hot. the top rad pipe is firm but not solid, and feels more like air than water but that might be wrong. also noticed that starting cold there is no smoke from exhaust but on coming up to temp it is smoking white smoke and dripping fluid, is this just because its been sat for a while, or do i need to rip out the engine, re build it and pop it in me 90? cheers

bigwill said:

ok well, the temp gauge comes up to the middle (directly pointing up) and stays there the bottom of the rad is still cold to touch at this stage, the header tank is not far off boiling and the heater is hot. the top rad pipe is firm but not solid, and feels more like air than water but that might be wrong. also noticed that starting cold there is no smoke from exhaust but on coming up to temp it is smoking white smoke and dripping fluid, is this just because its been sat for a while, or do i need to rip out the engine, re build it and pop it in me 90? cheers

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It is normal to get vapour from the exhaust after start up in cool damp conditions. If it has not run for any length of time there will be moisture in the exhaust system. This vapour should disappear in time. Run the engine a little longer at around 1500 rpm. Then check rad, if temp gauge goes much above normal stop engine. Maybe stat is sticky.

ok, thanks and the very hot header tank, is this normal?

bigwill said:

ok, thanks and the very hot header tank, is this normal?

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The coolant within the block heats first, that will include the header tank. Not until the coolant reaches full operating temp will the thermostat open allowing full circulation through the radiator. It's a case of suck it and see i am afraid.

try pulling the thin pipe at the top left of the rad (as your looking at it) see if air or water comes out
if hot water comes out its a good bet yor rads fooked if air comes out its eather just an air lock or your thermostat aint letting the water circulate

i have allways found when refilling the system is to fill it very very slowly so you are less likely to get an air lock

Discovered method to purge airlocks when refilling water /coolant after rad fit etc: prize top hose off at rad and fill here first. Refit, top hose then Lift the expansion tank up as high as possible out of its mounting,fill here whilst running and revving engine - all with interior heater set on max.

Just filled mine after rebuilding the engine.

Checked the air bleed from the top of the rad back to the expansion tank was clear.

Poured coolant into expansion tank through filler, it doesn't like going and squeezing top hose fast help remove some air. I got fed up with this and pulled the top hose off the radiator and filled the block from here.

Filled radiator too whilst the hose is off. Put the hose back on and gave it a good squeeze again and again until air comming back to the expansion tank stops gargling out, or becomes minimal, fill to the level.

With the top off the expansion tank I started the engine at fast idle 2k , water in the expansion tank drops, so I was ready to top up with coolant. It does drop. Filled to the level. More gargling as the air locks move about. In the cab I could hear the air moving from/too the matrix on on occasion, don't leave it to long like this, or warm up too much. Once it is topped up put the lid on and keep an eye on it, get it up to temp and check again. Only fill when cool, level is usually a little higher when hot.

Keep an eye on it, short journeys first. I was slowly topping up for a few days, now it has leveled and stopped.
There are high spots in the v8's that trap air, the only way to move them is to drive it and keep topping up. Ensuring the bleed back to the e-tank is free.

Level changes in the expansion tank hot to cold and depending on the gradient so it can be difficult to see if its using or loosing any. I keep an eye on mine constantly after my block cracking.

Cheers

i keep a check on mine every other day