Announcement

Collapse
No announcement yet.

Should there be water directly under radiator cap?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Should there be water directly under radiator cap?

    Simple question gents. Just had someone who opened radiator cap and expected water level up to the brim. I never claimed to be ace of physics, but since expansion bottle is on lower level than radiator cap, if topped to the brim surely all the water would just go into expansion bottle and down overflow pipe, wouldn't it? I always presumed topping water level up to about 1/3 to 1/2 of expansion bottle was fine?

  • #2
    Unless the rad is losing water, the level in the rad should be up to the cap with the level in the expansion bottle at about 30% (look for the level mark on the bottle as it should not be above this when cold). The rad expands into the expansion bottle as it warms up and then sucks back the same water when it cools down. If you are regularly showing low water levels when cold, you've probably got a leak or maybe pin holes in the rad top tank.
    Mike G

    Comment


    • #3
      Hmm.. Up to the radiator cap? I topped it up to the brim, but after I start engine it just sips it all down in quick whirl and stays well below level of expansion bottle pipe, can barely feel water level with finger behind bend, if I push string down there, it's soaking wet about 2cm below. Whole 1.5 litre bottle went in there. If I close the cap, expansion bottle is half full and engine doesn't suck it back in (it should, if it needs water so badly, no?).
      The rad is not leaking, have no wet patches under the car, no visible leaks anywhere else and expansion bottle never overflows. No white smoke from exhaust whatsoever, no wet carpets, no water in oil. Temperature is and always was sweet, no loss of power... Thought maybe it's the dreaded syphon from combustion gases - cracked head - warmed up the engine, closed cap, replaced expansion pipe with straight pipe and stuck it in bottle, put it up on cap level, accelerated for few minutes up to 3.5 on clock but no air bubbles or soda water effect in a bottle at all. But can't keep coolant level up to brim, the moment I start engine it just whirls down and stays way below cap level.


      Don't know what to think - massive air lock somewhere?
      Last edited by v0n; 11th June 2005, 18:44.

      Comment


      • #4
        I presume you are starting the engine from cold with the rad cap off and that is when you watch the level disappear. I'm pretty sure that mine doesn't do that (can't check right now as it's still warm from a trip down to Bristol). You should see a bit of movement as the pump tries to push the water around the system but not a large drop in the level if everything is in order.

        Try opening both the heater valves (front & rear) with the engine cold, then start up and watch the level in the rad. If it drops and stays low after you turn it back off, you could be moving air around the system with some escaping out of the rad cap hole. Turn off, top up with coolant mixture and start up again.

        Keep doing this (without letting the engine get so hot that it start spurting out boiling water at you) until you can start it without noticing any significant decrease in the level in the rad. When that happens you should have a fully filled system purged of any air but check your oil level as well just to make sure you don't have some sort of water leak into the crankcase (very bad!!!).

        Just looked at the picture again and realised your "rad" cap isn't on the rad top but inboard of the top hose closer to the engine. However, that still should not make any difference as the overflow pipe still runs off the rad cap housing to the expansion bottle, so coolannt should only flow out of the system to the expansion bottle when the water gets too hot and pressurised and needs to lift the cap and expand into the expansion bottle. Unless you have a leak somewhere in the system, once you purge all the air it shouldn't need topping up any more.

        Hope this helps.
        Mike G

        Comment


        • #5
          I would say looking at that picture you rad looks like it s been repaired or has a couple of small leaks on it. May only leak when hot and under pressure and probably dries up instantly with the heat?????????
          Say not always what you know, but always know what you say.

          My 4x4
          My choice
          Back off

          Comment


          • #6
            Originally posted by Koi
            I would say looking at that picture you rad looks like it s been repaired or has a couple of small leaks on it. May only leak when hot and under pressure and probably dries up instantly with the heat?????????
            I agree.The radiator looks like it's past its use by date and it is possible that when engine is cooling down air is being drawn back into cooling system through the fine cracks/holes instead of the valve on rad cap opening and drawing the coolant back in from expansion bottle.

            Neville
            Last edited by NiftyNev; 12th June 2005, 12:27.

            Comment


            • #7
              Nah, those stains on the picture are from ages ago, leaking hose, damaged paint on radiator.

              Topped the level up few times, drove around some more this morning, seems stable for the past 24 hours. So, looks like I've been driving with a bit over 2 litres of coolant missing after it was last changed by service in December, and yet temperature level would almost never reach middle of the scale. I'm slightly puzzled...
              Last edited by v0n; 12th June 2005, 16:11.

              Comment


              • #8
                Originally posted by v0n
                Nah, those stains on the picture are from ages ago, leaking hose, damaged paint on radiator.

                Topped the level up few times, drove around some more this morning, seems stable for the past 24 hours. So, looks like I've been driving with a bit over 2 litres of coolant missing after it was last changed by service in December, and yet temperature level would almost never reach middle of the scale. I'm slightly puzzled...
                The sender is high up on 2.4's, in the stat housing, if the water level is low, its not in water, so won't show much heat.

                If I close the cap, expansion bottle is half full and engine doesn't suck it back in (it should, if it needs water so badly, no?)
                Not really, the cap seals the system, it only opens and fills the expansion tank if the pressure reachs more than 0.9bar. Then it will let water into the expansion bottle, then when the temp cools, it creates a vacuum that sucks water back in the system via the cap till its full again.
                4x4toys.co.uk - Keeping you on and off the road...

                Comment


                • #9
                  water under rad cap

                  Originally posted by v0n
                  Simple question gents. Just had someone who opened radiator cap and expected water level up to the brim. I never claimed to be ace of physics, but since expansion bottle is on lower level than radiator cap, if topped to the brim surely all the water would just go into expansion bottle and down overflow pipe, wouldn't it? I always presumed topping water level up to about 1/3 to 1/2 of expansion bottle was fine?
                  The surf rad provides two functions, pressurises the system by keeping the coolant in, and by some magic also provides a vacuum to take coolant from the expansion tank if and when required. To check your water level is best from cold e.g. after left standing all night. Remove cap you should see water and the expansion tank should be about half full.
                  If not you may have problems with the cooling i.e. water pump or radiator needs flushing, attending to the symptoms promptly could save head gasket or clyinder head problems, WHICH YOU REALLY DO NOT WANT!!!
                  My Surf is in having major surgery, still waiting for final prognoisis (hope this is spelt correctly).

                  Comment


                  • #10
                    is that the same for the 3.0L i.e. water just under radiator cap when cold and expansion bottle half full ??????

                    Comment


                    • #11
                      The water level at the cap should be nearly full, in all Surfs, (and most cars). The expansion tank is only that, when the water is really hot it expands, then the pressure exceeds .9 bar (which the cap is rated at) it opens and lets water into the expansion tank. When the pressure lowers, a small valve in the cap opens to it suck water back in to the cooling system till the water level is up to the cap,about 1/2" below usually).

                      (Like I said before......)



                      Which is why, when if a head gasket fails, the cooling system is always over pressureised from combustion pressure getting into the cooling system, and it pumps all the water out past the cap and into the expansion tank, then out on to the floor. Then the car overheats, and if its a 2.4 the heads cracks.
                      .
                      .
                      .
                      .
                      .
                      .
                      Here endeth the lesson.

                      4x4toys.co.uk - Keeping you on and off the road...

                      Comment


                      • #12
                        Originally posted by TonyN
                        Which is why, when if a head gasket fails, the cooling system is always over pressureised from crank case pressure getting into the cooling system, and it pumps all the water out past the cap and into the expansion tank, then out on to the floor. Then the car overheats, and if its a 2.4 the heads cracks.
                        .
                        Here endeth the lesson.

                        Do you do this just to scare people???

                        Back in the world of Surfdom

                        Comment


                        • #13
                          Originally posted by TonyN
                          The water level at the cap should be nearly full, in all Surfs, (and most cars). The expansion tank is only that, when the water is really hot it expands, then the pressure exceeds .9 bar (which the cap is rated at) it opens and lets water into the expansion tank. When the pressure lowers, a small valve in the cap opens to it suck water back in to the cooling system till the water level is up to the cap,about 1/2" below usually).

                          (Like I said before......)



                          Which is why, when if a head gasket fails, the cooling system is always over pressureised from crank case pressure getting into the cooling system, and it pumps all the water out past the cap and into the expansion tank, then out on to the floor. Then the car overheats, and if its a 2.4 the heads cracks.
                          .
                          .
                          .
                          .
                          .
                          .
                          Here endeth the lesson.

                          Cylinder pressure Tony
                          Here correcteth the lesson
                          Rick...Member of 1st Gen club. ONE LIFE ... GET ONE !!

                          Comment


                          • #14
                            Originally posted by Vagrant No2
                            Cylinder pressure Tony
                            Here correcteth the lesson
                            yeah, I'll give you that.

                            Fixed it, apart from the spelling errors!
                            4x4toys.co.uk - Keeping you on and off the road...

                            Comment


                            • #15
                              Originally posted by Djandco
                              Do you do this just to scare people???

                              Who me? :innocent: Just saying how it is.....
                              4x4toys.co.uk - Keeping you on and off the road...

                              Comment

                              Working...
                              X