FD exapansion tank full when cold - problem?

[lockwood77]

Hi guys.

I have been religiously checking oil and water levels (both filler neck and expansion tank) before using the FD, as well as monitoring temps when in use.

I\'ve noticed that the expansion tank always appears to be full before I start the engine (over the full mark, I think, unless it can appear wet even though the level is lower?)

The level is high in the filler cap and hasn\'t dropped and I haven\'t seen evidence of any water escaping from the expansion tank overflow.

After an hour\'s searching/reading, I\'m still not entirely clear whether this is a real problem without additional symptoms - it seems that the level should be between the markers, as you\'d expect. I can also see that there may be a cause such as dodgy AST cap or hose preventing back-flow to the AST, hence the high expansion tank level when cold, but if water kept flowing one way when hot, wouldn\'t I see a drop in levels and overflow occurring?

I will do the champagne test tonight and check the AST level (haven\'t as yet as the filler neck has always been at the same high level), I may then go and warm her up and see if I can get an overflow to occur as the only other thing I can think is that the system is overfilled, but again, surely I would have seen this happen by now? Maybe I\'ve just missed it. :xconfused

Bit of advice from those with experience please! :Thumbs-up

[gsb876]

The filler neck level on mine is at the brim when car is cold, as it was with my last 2 RX\'s as well nothing to worry about with that.

The expansion tank has a overflow hole at the base of the neck and if overfilled will flow out of there.

Nothing out of the ordinary as far as i can tell, if it was overfilled it will level itself out from the expansion tank overflow tank.

[lockwood77]

Gurj, you always seem to have the words I want to hear!

What level is your expansion tank at when cold though?

[gsb876]

Gurj, you always seem to have the words I want to hear!

What level is your expansion tank at when cold though?

Err never really looked tbh because as long as the filler neck one is full then the system has enough coolant in there.

If the level in the filler neck drops dramatically then you want to pay more attention for sure, also i remember Pip telling me to never open the AST tank as you dont need to and never fill the AST when topping up.

Unless someone else has another opinion i dont think you have anything to worry about just yet, what mileage has the RX done on the engine ??

[lockwood77]

Only about 5k miles on the engine (Jimmy\'s standard rebuild inc. housings), so I\'m assuming it\'s nothing serious! :2Confused

[ash]

If your concerned then why not flush the system out and refill? Might be a good idea anyway if it has not been done. I did when i had mine just for peace of mind.

[lockwood77]

I think it was recently done actually, but Pete\'s on holiday at the moment so can\'t check (the chap I bought the car off if you\'re wondering! )

[Rocho]

also i remember Pip telling me to never open the AST tank as you dont need to and never fill the AST when topping up.

I had a lesson from Pip a few weeks ago and he told me to take off the AST and fill the neck until its half full. Its on the bottom of my "water usage" thread if you want the details.

[gsb876]

I had a lesson from Pip a few weeks ago and he told me to take off the AST and fill the neck until its half full. Its on the bottom of my "water usage" thread if you want the details.

Well he\'s changed his tune then as i was told never to fill the AST but only the filler neck which will then level out the rest ?? :Hammer

[arrouk]

dont worry about the expansion tank too much, unless its p1$$ing water out or always needs filling, its just a reserve of water for the cooling system to both expand into but also draw back from if required........or so i believe.

as long as its at the top on the filler neck, or just below there is no prob.

also dont do too much work on the engine until you speak to the builder as this may affect the warranty.

matt

[lockwood77]

Cheers guys. Engine is out of warranty, so not worried in that sense, but would obviously prefer it if it was!

Didn\'t get chance to look last night in the end, will post back when I do.

[Rocho]

Well he\'s changed his tune then as i was told never to fill the AST but only the filler neck which will then level out the rest ?? :Hammer

No you dont fill via the AST, you fill via the neck until the level in the AST is over half full. I was referrring to your comment about never removing the cap to the AST.

[lockwood77]

Well, I checked the levels in all three areas (expansion, filler, AST) and they were all maxed, so I\'ll take that as fine so long as the levels don\'t drop. The expansion tank was so full it\'s way over the full mark and creeping up the narrower top half of the dipstick!

I guess the system is pretty full, so at some point I expect it will eject some water via the overflow hole; maybe I haven\'t got it hot enough yet to do that? Haven\'t seen anything over 100 degrees, and that was from heat soak when starting up, not during a run.