Grubbster Posted June 21, 2011 Share Posted June 21, 2011 I have a strange problem with my K series car. In summary - when working it hard on track the expansion tank fills with coolant even though there are no noticeable temperature issues. I have no idea what is making this happen but clearly would like to resolve it ASAP. A bit more detail: The engine is a high powered K series (1800, 230 bhp, dry sumped) that I fitted last year. The problem occured at all 3 trackdays last year. The engine has just been refreshed (no head gasket issues found) and it did the same on track yesterday in every session. I don't think there is anything wrong with the build of the engine. It doesn't seem to be a temperature issue nor is there a build up of pressure - a few minutes after each session I removed the top bolt from the rad, loosened the expansion tank cap - allowing the fluid to drain back into the rad and the level in the expansion tank dropped to where I would expect it to be. It does not appear to have boiled. The temp gauge doesn't go over 80 and the fan does work. If I leave the car idling it all works as expected (temp rises, hoses get hot in the correct sequence, fan cuts in, temp drops, fan cuts out - all good). I have just completed a 2000 mile round trip to Stelvio and although I had a tiny leak from the water rail gasket (now fixed) and some signs of pressure release on the expansion tank (at altitude) it all worked fine. There are no leaks and I am pretty confident there are no airlocks (it has been bled many times over). I have tried several expansion tank caps. Recently I removed the thermostat and fitted a PRRT. I do have a heater and a bleed T in the heater hose. I have tried by-passing the heater but it made no difference. So what is the cause of this? On track the engine is under sustained loads for longer, revving to some way beyond 8000 rpm, cornering speeds are higher. A friend drove in one session and he revved it a lot less but the same thing happened (albeit it only moved the level in the coolant tank up to 3/4 - not full). I really don't know what to try next and this is curtailing my trackday fun again this year so I need it sorted (and not by fitting a duratec ). Could it be water pump? Would the high revs cause a problem there? Should I take out the PRRT and just fit a remote stat (QED)? Can I get the system pressure tested easily? This is one for the POBC - please give me some clues Edited by - grubbster on 23 Oct 2011 14:42:41 Link to comment Share on other sites More sharing options...
shn7 Posted June 21, 2011 Share Posted June 21, 2011 Grubbster, Sorry to hear this problem persists. I wonder if there's an issue related to pulley sizes and revs resulting in the water pump running too fast? I don't think that altitude up Stelvio should result in any change in a sealed system since the pressure internally should remain unchanged surely? Different matter on air/fuel mix being open to the atmosphere. Good luck in finding the problem. Link to comment Share on other sites More sharing options...
djg Posted June 21, 2011 Share Posted June 21, 2011 Are you always bleeding water off and never filling it up? The fluid must come from somewhere? I have seen similar on my car, but I put that down to the heater being above the max mark on the exp tank, I would fill the car cold and bleed leaving air in the exp tank, do a run and then find the exp tank brimmed. Release some coolant whilst hot and then carry on. When cold I would have not enough coolant, refill and bleed from the heater with the front in the air and the cycle went on. In the end I left well alone when it was hot, and then corrected the level when cold after a track day. All has been fine since. I think they need a bit of air in the heater otherwise the air wants to go to the top, which on mine at least appears to be the heater matrix and hence the exp tank fills up. The heater still works and the temps are fine I have a K 1.6 SS, c/w dry sump, fresh air heater, flat exp tank radtec rad and boggo stat. Doug Link to comment Share on other sites More sharing options...
Grubbster Posted June 21, 2011 Author Share Posted June 21, 2011 I never need to remove any fluid, I just let it find its way back into the rad where it belongs by releasing the top bolt (to let air out) and the expansion tank cap (to let air in) - I just cant work out why it ends up the way it does after a thrashing. When I bypassed the heater it made no difference but maybe I should try that again and see what happens. I have heard from a couple of sources that the PRRT is not a great idea for the 7 so I might take that out and fit a remote stat instead. But the symptoms have been the same before and after PRRT so I suspect that isn't the cause of my problems. I did think I had fixed it last year when I noticed the system was losing a little pressure from a loose fan switch, but obviously this isn't the cause after all ☹️ Link to comment Share on other sites More sharing options...
andy_h Posted June 21, 2011 Share Posted June 21, 2011 Water is being pushed from the rad into the expansion bottle and the space in the rad replaced with the bottle's air (assuming the system is sealed and no air leaks) By releasing the rad bleed screw you're allowing air out and water to run back into the rad from the bottle (releasing the expansion cap allows this to happen due to air lock). Query - Could the water be pushed into the bottle before it can get into the rad? Water pump problem? Do you have a restriction in the pipes/rad preventing good flow? What about process of elimination - borrow a good rad to try. Are you sure you don't have a restriction in a pipe. Are all the pipes connected the correct way. Pump running too fast pushing the water in to the bottle as it's pumping too fast to get into the rad I could be talking twaddle 😬 Link to comment Share on other sites More sharing options...
CageyH Posted June 21, 2011 Share Posted June 21, 2011 Are all the coolant hoses in good condition, and the clips well tightened? Do you still have the restrictor in the feed from the head to the expansion tank? You have to have air entering the system somewhere, you just need to find it. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted June 21, 2011 Share Posted June 21, 2011 It sounds like a very slight HG leak or a small crack in the head, I would get it pressure tested as it won't go away. Air is being introduced to the system somewhere and it shouldn't be. If it were not being introduced then bleeding it off as you do would fix it and you wouldn't need to do it repeatedly. A leaky water pump lets water out not air in. Link to comment Share on other sites More sharing options...
Grubbster Posted June 21, 2011 Author Share Posted June 21, 2011 Thanks for the ideas chaps - more for me to think about. All hoses are new, sealed, good clips etc. The engine has just been rebuit so that should all be OK. I don't think the rad has any blockages - it is pretty much as new. I don't think air is getting in anywhere - just air and coolant seem to be swapping places internally IYSWIM What is the restricter in the feed from head to expansion tank - I don't know what this is about so maybe something to check? Certainly with the engine running I can see fluid pumping into the expansion tank from the pipe that comes from the inlet side of the engine - quite a good flow - is that good or bad Link to comment Share on other sites More sharing options...
Grubbster Posted June 21, 2011 Author Share Posted June 21, 2011 BOSS - when you suggest pressure testing do you mean with it all installled as iit is (rather than removing teh engine again)? If so then that sounds like something well worth arranging. I'm not convinced air is entering the system but certainly will investigate further. Link to comment Share on other sites More sharing options...
CageyH Posted June 21, 2011 Share Posted June 21, 2011 On the header tank outlet in the original plastic inlet manifold, there is a small restrictor to limit the flow to the expansion tank. If this is the easiet path, then guess hwere all of your water will go..... Link to comment Share on other sites More sharing options...
Mr Locust Posted June 21, 2011 Share Posted June 21, 2011 Do you have a sketch of the prrt circuit you have installed? Link to comment Share on other sites More sharing options...
Sheds Moderator Posted June 21, 2011 Share Posted June 21, 2011 Quoting Grubbster: BOSS - when you suggest pressure testing do you mean with it all installled as iit is (rather than removing teh engine again)? If so then that sounds like something well worth arranging. I'm not convinced air is entering the system but certainly will investigate further. Yes, that's it precisely. It's an in situ test, no dismantling required. At the same time the garage can do a test for combustion products and gases in the coolant, if they are present there is a problem. The pressure test is that with the engine stationary you connect a replacement water cap to the header tank and pressurise it with comp air. You then watch the pressure, which should be static, any leaks will become apparent, either by coolant leaing out or coolant leaking inside the cylinders or the sum poil. Link to comment Share on other sites More sharing options...
Team Escargot Posted June 21, 2011 Share Posted June 21, 2011 Martin I had a similar issue some years back with a tuned twincam - bearing in mind that the expansion tank is there to provide a reservoir for the water to go when it is heated (basic physics). However, if it is filling up completely then something is wrong! The things I found were: The temperature around the head and block varied (as in any system) because of the variable metal thickness around the combustion points (heat sink) – although the water ways around the head and block are strategically placed in an attempt to control these rises in temp they will never be able to smooth them out completely - this gives rise to local hot spots. All IC engine are basically heat engines and the more they are tuned the greater the heat produced. This means the hot spots get hotter which can lead (and in my case) to localized boiling of the coolant which rapidly expands and has to go somewhere - ie the expansion tank. On a K series modified head some of the water ways are deliberately plugged to allow the ports to be opened up - I would guess that this may increase the hot spot issue. So what I did was to increase the flow from the water pump (by fitting an electric hi flow rate pump) this had the effect of ensuring that the heat was taken away as soon as possible. This seems a bit extreme for a K so I would check the flow from the water pump first (or just check that the vanes are not missing or corroded away). (Note pressure and flow rate are different) Not sure what water temp sender/gauge you are using - if it is standard CC then its not very accurate - I got a reading of 80deg C with a standard set up but now with an SPA it shows a more realistic 98 when waiting to go on track. (could be worth checking expansion tank without any air flow through the rad!) Hope this helps - (but I am sure wiser minds than mine will discuss this issue) Nick Link to comment Share on other sites More sharing options...
Eugene Posted June 21, 2011 Share Posted June 21, 2011 I had a similar problem on my Elise... The water level in the header tank would rise as the engine got hot (not overheating though). The reason was the rad cap was faulty, and was allowing air to leak, but not water, so the water level rose. Link to comment Share on other sites More sharing options...
Grubbster Posted June 21, 2011 Author Share Posted June 21, 2011 Ian, I rigged it up as per this diagram - the PRRT in the diagram is a little misleading though as the shape is not quite right - but it shows the circuit. Link to comment Share on other sites More sharing options...
henry21p Posted June 21, 2011 Share Posted June 21, 2011 I've had this a few times on my car over the years. Usually been as a result of small amounts of air getting into the system and expanding. 2 different causes so far. First was small cracks in the hoses that opened up under load on circuit. The other has been a persistent weep between the water rail and the head. You can normally tell that one from white dried deposits from boiled off coolant dripping under it or running down the back of the engine. With my car, I could drive all day ,or pootle around on track at warm up speeds and it was fine. As soon as I hit traffic (and therefore lost cooling effect of running), or gave it some beans, the extra loads or temps caused expansion bottle to overflow. No temp problem and the system was properly bled. Water rail off, new gasket and sealant and checked hoses for airline cracks and holes around the hose clips. Link to comment Share on other sites More sharing options...
henry21p Posted June 21, 2011 Share Posted June 21, 2011 Oh, and once it was the cap too. Link to comment Share on other sites More sharing options...
F355GTS Posted June 21, 2011 Share Posted June 21, 2011 I see my suggestion of fitting a duratec has been discounted Have you done a hydrocarbons test of the coolant? if the HG or head is leaking air in when under load then this should show, I've a tester which you'd be welcome to borrow but ti's packed for the move so won't be available for a few weeks, sorry Link to comment Share on other sites More sharing options...
henry21p Posted June 21, 2011 Share Posted June 21, 2011 Without being dismissive - I might be showing my ignorance - but the times that i've had HG problems, under heavy driving loads and temps, the symptoms have been farmore spectacular than those described. I didn't take up the offer of the tester all those years ago when i first started having problems.... but a few dramatic failures and boil-overs highlighted that when there's a HG prob, it's a bit lairy. I've heard lots of talk about porosity and "slight leaks" but from experience of many many years of failures, this sounds more like an air getting in to the system than a water/cylinder or water/oil mixing prob. However, please don't turn down the offer of the tester - it's a cracking idea and piece of kit and will give you peace of mind! Link to comment Share on other sites More sharing options...
Grubbster Posted June 21, 2011 Author Share Posted June 21, 2011 I'll call the guy that built the engine tomorrow and see if he has the necessary kit to check the coolant and to do the pressure test, hopefully he'll be able to work out what is wrong. It is a cracking engine, very strong so I hope I can fix this problem and get it out on track a bit more! Link to comment Share on other sites More sharing options...
shn7 Posted June 22, 2011 Share Posted June 22, 2011 Grubbster, Thinking about where air might be getting in and knowing how much you're replaced, could there be a pin hole in the header tank. Might be enough to let air through and if near the top any coolant would be suspected of escaping from the cap. As others have said, pressure and HC test sounds like the way to go. Link to comment Share on other sites More sharing options...
Grubbster Posted June 22, 2011 Author Share Posted June 22, 2011 Steve, worth checking but I don't think I am losing or gaining any air or any fluid - the total contents of the system don't change, no fluid loss, no pressure release when I open the cap. I haven't managed to call Tom yet but I will do - HC and pressure test are certainly the next steps. Back to Cageys point - there is quite a strong flow from the pipe connected through the inlet manifold and this goes straight into the header tank. It could be that this flow is so high it starts pushing the air from the header tank into the system via the submarine and hence into the rad (assuming that under high cornering forces the air pocket in the expansion tank could become aligned with the outlet hose IYSWIM)? Maybe I need a different shaped expansion tank. Hmm, it could be worth rigging up a little video camera so I can see what goes on . . . . Link to comment Share on other sites More sharing options...
CageyH Posted June 22, 2011 Share Posted June 22, 2011 It may also be that the expansion tank is not at the highest point in the circuit. Is it still on the original location? I have mounted mine on the front of the heater, as I got fed up with having to take the nose cone off to check the levels. Link to comment Share on other sites More sharing options...
Grubbster Posted June 23, 2011 Author Share Posted June 23, 2011 The heater is probably the highest point, expansion tank is mounted in the standard place. I'm becoming more convinced that the air is being drawn out of the expansion tank during in high speed right turns (as at Castle Combe) as the fluid sways to the left of the tank - and that the fluid is going into the tank at pretty high speed from the outlet from the inlet manifold at the sustained high revs. The air ends up in the top of the rad. I will look at the alternate expansion tank (square one) to see if it would be any better at stopping this. Baffled expansion tank needed maybe 😬 Link to comment Share on other sites More sharing options...
shn7 Posted June 23, 2011 Share Posted June 23, 2011 Baffled expansion tank needed My older style square one is baffled I'm sure. Is the round one not then? Link to comment Share on other sites More sharing options...
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