Advice: changing the thermostat + coolant this weekend...

...never doen it on a V8 before, anything I should know about? For instance, a coolant change in a Beemer can be a right bugger to do as it's really easy to get air locks in the system!

I know I need to drain the coolant to get to the thermostat, do I have to drain the lot? It was changed just before I bought it, so I plan to reuse it providing it looks nice and clean still!

Is it just the usual procedure - undo expansion tank and radiator caps (when cold!!), remove bottom hose and drain. Remove and replace thermostat + gasket. Refit bottom hose - then where do you fill it up from, the expansion tank or radiator? Any tips for not getting any air locks in the system?

Cheers!

dead easy this one , drain as you said . to refill use the brass plug , if you have one . IF your plug is there but plastic get a brass plug before you attempt this . there should be no issues refilling as regards air lock's . you may have a bit of fun bleeding the system if you have an LPG conversion . I say this as I have an lgp conversion and no plug so mine's a sod to bleed .

Err..I do have an LPG conversion, what effect would that have on the cooling system though!

No idea what or where this brass plug is...can you enlighten me please?

I guess he is refering to the radiator plug on the top, some where plastic and some where brass....

Yours is a 1994 and should have an upright filler tube next to the plenum chamber to make filling and bleeding the system easier as this is the heighest point in the system....

The reason LPG is a sod is because oftentimes, the LPG Vapouriser is higher than the rest of the cooling system and can trap air pockets in it as it is heated from the cooling system....

But my '93 had LPG and also this upright filling tube so wasn't to bad as this tube was higher than the LPG Vapouriser....

Picture of filler tube attached...........

Thanks Saint! That does look familiar - so I fill it through there, not the radiator then?

I took the plug out of the top of the radiator and the Expansion Tank....

I filled the rad up, the tank up and then filled through the top tube until the water ran out of the radiator with our bubbling, I then put the rad plug back and continued filling through the top tube.....

Keep burping the hoses through out....

Hi Mike,
I have had trouble with this last weekend on my 1973 2-door with a 3.5l V8. I dropped the coolant to get the radiator recored but had problems refilling. The workshop manual says add 4.5litres of water to the rad then "add 6 litres of antifreeze and top up with water". Itr doesn't say where to add the 6 litres so I carried on adding to the rad. Trouble is you can only get another litre in before its full. Tried squeezing hoses etc to get air out but still can't get any more than around 5.5litres in.

Others have recommended running the engine and then adding more coolant after its cooled again but not had chance to try this yet. The manual doesn't say you need to run the engine.

If you want to do a proper drain and refill, you can also remove the drain plugs from the engine block, which will apparently drop a lot more of any crap that's knocking around in there. I could see mine shearing off or not sealing again, so I left them alone.

One other thing, if you're going to reuse the coolant, make sure it doesn't get too damp whilst it's out of the engine, or you'll not be able to use if again.

have a blowlamp ready incase your stat housing bolts are siezed and some copper slip to put on the bolts when they go back

blue hylomar for the mating faces with a new gasket.

you dont need to drain it all , I sucked out what was in the header tank with a big seringe (spelt wrong) and then put a rag or two in the valley before I took the housing off. I lost a bit but not much. I then topped up throught header tank then fill tube untill it was at it corect level and ran it up to temp withe the caps off to allow it to expell air. as soon as it started over flowing put the caps on run it round the block and leave to stand over night and top up in the morning and all air should be out.

jiggle pin at 12 oclock on stat btw and make sure its a waxstat one

Cheers fett! Where in South Hampshire are you? I'm down that way tomorrow - Portsmoutjh/Gosport area!

Twice I've done this and twice there's been an airlock. No hot air coming through the heaters and LPG coolant pipes freezing as the engine was warm..... Took off the top rad plug and gave it a good few revs to get a bit of a splutter......then refilled until the water was over flowing. Heat then came through the vents and all was restored to norm.

Good luck

DC_ said:

Twice I've done this and twice there's been an airlock. No hot air coming through the heaters and LPG coolant pipes freezing as the engine was warm..... Took off the top rad plug and gave it a good few revs to get a bit of a splutter......then refilled until the water was over flowing. Heat then came through the vents and all was restored to norm.

Good luck

Click to expand...

Well....I was gonna try it this weekend, but the thermostat hasn't bloody arrived yet! Typical!

However, I don't seem to have that filling pipe some posted a picture of earlier, which I was expecting to have on my 1994 model. Would it have been removed when the LPG kit was fitted?




So do you just keep adding water to the top of the radiator rather than the expansion tank to get rid of the airlock then?

i dont think air bleed was fitted on serpentine belt engines ,just ensure heaters on hot and fill as much as you can run engine till heaters warm and keep topping up.check all hoses get warm so you know there all full

Thanks James. So fill the radiator (And expansion tank?), start the engine, heaters and fans on full, then keep topping it up...through the radiator or expansion tank?

fill till rad overflows fit bung the do the rest through expansion tank ,worth rechecking after a run up the road

I've never used my "highest" point to fill the system...... I have LPG but its not serpentine
..... You could also lift the front of the beast up to make sure it's the highest point?
Yes I would use the rad filler rather than the expansion tank. Give it a good rev ( watch yer hands etc as it'll be roastiing)

same as I said before mike , just the rad first then tank but you dont have a fill tube so gotta stop at the tank

all the rest the same though

OK, cheers guys. Fett - just concerned about the complications of the LPG kit!!

yes true, not had to deal with that one. if you run it till overflowing out the header and put the lid back on and drive it and then stand over night before topping up that should do it though. you wont have lost too much doing it my way in the first place I dont think.

Well, because of continued rain and freezing temperatures I took it to Goodyer 4x4 on Friday morning and they swapped the stat over for me. I say swapped - fitted the thermostat was more accurate, as when we took the elbow joint off we found there was no thermostat in there at all - brilliant! Explains why the engine wouldn't retain heat in cold weather, then.

After 20 nervous minutes whilst we waited to see if it had been removed due to an overheating problem, all seems to be OK and running good as gold.

Weirdly, the mechanic only remvoed the expansion tank cap and refilled it through there too with the engine running. No sign of air locks, the top hose got warm when the stat opened and remianed nice and soft. Just need to top up the anti-freeze as it dropped overnight, which is to be expected. But no messing around with the radiator or any of that!