Grubbster Posted June 23, 2011 Author Share Posted June 23, 2011 Nope, it is like a soup bowl! Link to comment Share on other sites More sharing options...
Mr Locust Posted June 23, 2011 Share Posted June 23, 2011 The expansion tank is effectively at the highest andthe lowest point in the circuit - in pressure terms. The small hose is connected to the head (pump delivery). The large hose is collected to the bottom hose (pump suction). If your theory about drawing the air into the bottom hose holds good, would you agree that restricting the flow through the small hose to the bottle would reduce that tendency? To the limit where blocking it (once bled) would allow no flow and no drawing in of air? What thermostat temperature are you running? Is the engine getting hot enough for the coolant circuit to pressurise? Link to comment Share on other sites More sharing options...
oilyhands Posted June 23, 2011 Share Posted June 23, 2011 In my experience, 'air' continually appearing in the top of the rad and coolant tank levels rising in the header tank are an indication of an early HGF across the fire ring. Oily Link to comment Share on other sites More sharing options...
F355GTS Posted June 23, 2011 Share Posted June 23, 2011 Quoting Grubbster: 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 😬 I think the 8v VXs may have suffered from a similar problem and recall reading about some sort of restricter in the pipe from the inlet manifold to header tank Link to comment Share on other sites More sharing options...
jakeandlizzy Posted June 24, 2011 Share Posted June 24, 2011 early HGF across the fire ring Could another source not be the intake manifold? I had this issue and symptoms when I didn't seal my Jenveys correctly -- 3rd time was charm... Link to comment Share on other sites More sharing options...
Grubbster Posted June 24, 2011 Author Share Posted June 24, 2011 I will get the coolant checked for any signs of HG failure - but I'd be surprised if it is this as it did the same before the engine rebuild and it does it now since teh rebuild. There was no sign of HG problems when it was stripped - but I suppose it could have had a problem we didn't see. Maybe there is a problem with the head itself - I really hope not! Link to comment Share on other sites More sharing options...
Sheds Moderator Posted June 24, 2011 Share Posted June 24, 2011 Did your man crack test it as part of the rebuild? Would have been a good precaurion bearing in mind your symptoms. Link to comment Share on other sites More sharing options...
Grubbster Posted June 25, 2011 Author Share Posted June 25, 2011 Being pressure tested and HC tested next week. I'm going to fit the older style expansion tank and a restricter in the inlet hose - these 2 things should improve it. I may then look at removing the expansion tank and fitting an in-line filler cap to cure it completely. I'll update the thread when I know more. Link to comment Share on other sites More sharing options...
Jason Plato Posted June 25, 2011 Share Posted June 25, 2011 let's not be in denial , the head gasket has gone. the head is probably soft from the last failure. whip the head off and get the firing rings area hardness tested. hundreds of caterhams have the header tanks and they dont have air drawn into the system from the header tank ..... Link to comment Share on other sites More sharing options...
richy Posted June 25, 2011 Share Posted June 25, 2011 I have seen pump shaft mechanical seals which have pulled air in to cooling systems when running, but appear leak-free when stationary. Admittedly these weren't on car engines. Could the CW Pump seal be slightly damaged? richy Link to comment Share on other sites More sharing options...
Grubbster Posted June 25, 2011 Author Share Posted June 25, 2011 let's not be in denial , the head gasket has gone. the head is probably soft from the last failure. I might be in denial - I will know soon. There wasn't a 'last failure' the recent build was just a precautionary strip/build with new big ends, seals, rings and valve springs. I agree that hundreds have header tanks and not all have problems and that is the confusing bit. I have no problem either unless I am revving the nuts off on track and I guess the majority of owners don't do this. So I am clinging on to a hope that the header tank design and flow rate of coolant are the reasons why I have problems. CAr is going back to the engine builder shortly so should have a few more clues soon. It did exactly the same before it was rebuilt so it has either always had a problem - or there is no problem with the engine and it is (hopefully) just a cooling system issue [fingers crossed] Link to comment Share on other sites More sharing options...
Jason Plato Posted June 25, 2011 Share Posted June 25, 2011 there are also hundreds of Caterham k series race cars revving their nuts off every weekend Edited by - Dave Jackson on 25 Jun 2011 20:00:03 Link to comment Share on other sites More sharing options...
Grubbster Posted June 25, 2011 Author Share Posted June 25, 2011 Good point I'm clutching to the straw that Academy, RSA and RSB have a reduced coolant flow from the inlet manifold and they don't actually rev that high - but I have no answer to all the others out there that rev high, run slicks etc 😬 If it is head gasket I'm not too worried but if it is head then that sounds expensive Link to comment Share on other sites More sharing options...
weeman Posted June 25, 2011 Share Posted June 25, 2011 Hi Steve, this may be a dumb question (wouldn't be the first time 😬), but do you know whether the coolant levels return to normal once they have cooled down a little? (i.e. without your intavention). I ask this because the coolant level in my 7 is always slightly higher when hot than when cold. Dumb question number two; if your car is running well, not over heating, not loosing coolant and not boiling over and the coolant level does return to normal when cool.....do you really have a problem? Be lucky!! Martin Link to comment Share on other sites More sharing options...
Grubbster Posted June 26, 2011 Author Share Posted June 26, 2011 Hi Martin - not dumb questions at all 😬 If I leave it to cool it doesn't find its own level unfortunately, the air pocket is trapped in the top of the rad so I need to loosen the bleed screw on the rad and the expansion tank cap and let it settle (a few seconds). But other than this problem it runs absolutely fine, very odd Link to comment Share on other sites More sharing options...
oilyhands Posted June 26, 2011 Share Posted June 26, 2011 It is perfectly normal for the coolant level to be a CM or so higher when the engine is hot. Continual bleeding from the rad is indicative of HGF. Normally any air drawn into the block will exit from the bleed at the front of the block. Oily Link to comment Share on other sites More sharing options...
Grubbster Posted June 26, 2011 Author Share Posted June 26, 2011 Thanks Oily - can I just clarify something please? Which pipe is the bleed at the front of the block? If the gases make their way to the rad then I assume the fluid in the rad gets pushed into the expansion tank and the air in the expansion tank gets pushed out through the cap? I will know more next week after the pressure and HC tests but I'm keen to understand more about how it all works I also noticed a photo of my engine on your website (It was Rob Walkers) Link to comment Share on other sites More sharing options...
oilyhands Posted June 26, 2011 Share Posted June 26, 2011 The bleed is the spout on the front of the TBs... it is the highest point on the block/head assembly. Oily Link to comment Share on other sites More sharing options...
pburt Posted June 26, 2011 Share Posted June 26, 2011 Grubbster, I will be very interested to learn how your tests go as I have EXACTLY the same issue with mine (1.4 SS). As you say, it's as if the air and coolant are swapping places, without apparently losing or gaining either - the level simply returns to normal when you allow the air out of the top of the rad and allow air back into the top of the expansion tank. Water temp remains normal and the engine seems to perform in good health. What I think I have noticed out of the ordinary is that the water seems to be getting up to operating temp more quickly than it should - i.e. fully up to temp within 2 or 3 miles of gentle driving. Have you noticed anything like this? Peter Link to comment Share on other sites More sharing options...
Grubbster Posted June 26, 2011 Author Share Posted June 26, 2011 Hi Peter, in a way I am glad someone else has the same issue if you see what I mean, I have also had some emails from people who have also experienced the same problem. Mine doesn't seem to warm up any differently to what I'd expect - but I have only had this engine fitted for 18 months so not much to compare with except my previous engine - and it seems to be very similar in the way it warms up. It has always done the same trick with its coolant at Castle Combe - both before and after the rebuild. It managed 2000 miles around the Alps recently with no significant problems. I look forward to finding a definitive answer and solution! Link to comment Share on other sites More sharing options...
Mr Locust Posted June 26, 2011 Share Posted June 26, 2011 A fundamental difference between road and track tends to be the duty cycle of the engine. Higher duty cycle gives higher cylinder pressures which would tend increase any gas leakage however marginal. How much fuel did you use per hour in the Alps compared to on the track? Link to comment Share on other sites More sharing options...
pburt Posted June 26, 2011 Share Posted June 26, 2011 Grubbster, mine only started behaving like this recently, after replacement of the water pump (it was leaking) and a re-core of the radiator (ditto), carried out in conjunction with cambelt/tensioner replacement. At the same time I had the cylinders pressure tested to check there were no lurking head-gasket issues (just for peace of mind, not because I had reason to suspect there was a problem). The tests were fine, which is why I am sceptical of HGF being the automatic explanation. Good luck with your tests; I hope you get a conclusive result. Will watch this space! Peter Link to comment Share on other sites More sharing options...
pburt Posted July 2, 2011 Share Posted July 2, 2011 Hi Grubbster Any news? Peter Link to comment Share on other sites More sharing options...
Grubbster Posted July 2, 2011 Author Share Posted July 2, 2011 Not much to report - as I work away during the week it is hard to get it into Toms for the work to be done. Caroline has kindly offered to take it in for me on Wednesday. Tom is very confident it isn't head or head gasket but he will check for HC in the coolant and do a pressure test before anything else. The plan is to remove the PRRT (that I just fitted ) and fit a QED remote stat instead (Toms recommendation), replace the expansion tank with the old style one and maybe put a restricter in the engine bleed pipe to reduce the flow from this point (as there is in the cars fitted with a plenum). Hopefully this will make a difference. I've now heard from several people with similar problems that haven't been able to resolve them so maybe it is a bit more common that I expected Keep those fingers crossed a bit longer! On the fuel consumption question I can only answer roughly - normal use I get 200 ish to a tank. On route through France I actually managed 233 (by accident - took a while to find a petrol station open!). In the mountains this dropped to about 160 and on track 90! So yes, certainly more cylinder pressure. Link to comment Share on other sites More sharing options...
pburt Posted July 2, 2011 Share Posted July 2, 2011 Thanks Grubbster, good luck for wednesday. Mine's just got a standard thermostat (renewed as a possible cure when the problems first arose) and the original, rectangular expansion tank (complete with restrictor in the top pipe). Having not had the problems prior the the radiator re-core and new water pump, I'm inclined to think the problem may lay in one of these. I'm wondering if it's possible for the water pump to be pumping at too high a pressure? I'm sure I'll just have to book mine in to get everything checked but it'll still be good to know how yours gets on. It's interesting that it seems to be a common problem (and a common mystery ) Cheers Peter Link to comment Share on other sites More sharing options...
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