revilla Posted August 23, 2013 Share Posted August 23, 2013 Yesterday I finished putting my VVC back together and had an absolute bitch of a job bleeding the air locks from the coolant (as many people do), even the "Peter Carmichael" method wasn't working, basically I wasn't getting any return flow from the bottom of the radiator and the bottom hose stayed cold while the engine just kept getting hotter. Heater was working fine, bleed tee bled coolant not air, radiator cap same ... so don't know where the air was, but unfortunately after messing with it for hours I found the inlet manifold gasket wasn't sealing so I had to drain it all again! Grrrrr ... Replacement gasket of quality now on order, so I will have to go through game again in a few days. Anyway, my question is this: While running and testing it, obviously it was getting hot, and hotter than its normal running temperature. I was a bit paranoid about cooking it so I didn't let it get too hot but I was wondering - while running it and pumping and massaging pipes to try to get things moving, how hot is it safe to let the coolant temperature gauge go before killing the engine? I can't seem to find specs for the temperature at which you risk affecting the heat treatment of the alloy. I guess with air locks there could be pockets of air in the head causing local hot spots too. I just don't know how far its safe to let it run. Link to comment Share on other sites More sharing options...
garybee Posted August 23, 2013 Share Posted August 23, 2013 If it's airlocked there's no guarantee that the coolant temp sensor is providing useful information anyway. No coolant flow means the heat staying in the head/block as opposed to being transported away/past the coolant sensor. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted August 23, 2013 Share Posted August 23, 2013 Have you done the coolant circuit mod as per LF article in Sept 2012 ? Easy and cheap. Mine now warms up quickly to 80C and stays there. Made it easy to fill and chase the air out. Link to comment Share on other sites More sharing options...
Bob L Posted August 23, 2013 Share Posted August 23, 2013 The Coolant mod worked well for me but I did install the bleed tee at the same time. Drained and refilled twice now with no issues. Did you remove the radiator bleed bolt (not sure of its correct term)? I fill up until coolant is present here, replace the bolt then fill very slowly via the bleed tee. This will always leave a little air in system (normally the heater) but flushes through easily once warm, then just top-up. PS Thanks for the details on the oil filter adaptor and temp sensor, all purchased and just waiting on the next oil change Link to comment Share on other sites More sharing options...
simonpa Posted August 23, 2013 Share Posted August 23, 2013 Never had a problem with the old-fashioned method.. Jack the car at the front as high as you can. Fill via the expansion bottle - leaving the bleed on top of the rad open - or the filler cap if using a standard rad. Start engine with both caps/bleed valve open. squeeze the top and bottom hoses to encourage air out of the big hoses. Need to get the engine up to temp to open the thermostat a release the last bit there - should happen OK before the coolant gets hot enough to expand/boil - at this time the bottom hose gets hot. Put the caps back on. May need to allow to cool and top up again. Link to comment Share on other sites More sharing options...
revilla Posted August 23, 2013 Author Share Posted August 23, 2013 In my case it just didn't happen, did everything everyone has described, filled slowly from the bleed tee to the point where every possible bleed point (radiator bleed screw, expansion bottle, bleed tee at heater) had water underneath it not air, but the bottom hose never got warm, never mind hot. Stone cold even as the car approached boiling. I suppose this means my thermostat wasn't opening at all, and since everything was fine before I changed the head gasket it's too much of a coincidence to think that the thermostat spontaneously failed while I was pulling the head off, so I can only assume the temperature sensitive part of the thermostat was sitting in an air pocket. There was clearly a lot of air still in there somewhere as with the expansion cap off the level rose dramatically as the engine heated up, then fell back dramatically as it cooled down, and water doesn't expand to that degree whereas air does. I don't know whether mine has had the bleed hole drilled in the thermostat. All I can say with certainty is that by the time I come to try filling it again next week (after my new gasket arrives) it will have! Hopefully when I pull it off I will find that this is the problem and therefore a simple fix. My main question though still stands - and garybee I totally take your point that the temperature sensor is not very useful if water isn't circulating - does anyone have any idea how to tell how long it is safe to keep running the engine trying to get it to circulate without running the risk of damaging it? Obviously it needs to run up to and beyond the normal thermostat opening point before you know you've got a problem, at which point if things aren't circulating you could already have some very hot spots in the head. My head gasket failure didn't seem to be caused by gross overheating and before I did the repair it never went above say 85C on the gauge, spending most of its time hovering around 80C. My head actually looked in very good shape, flat, no obvious signs of having been cooked, no signs of porosity or of the liners hammering into the fire rings, but I know how fragile the K can be if it gets too hot and I want to keep it like that. Bob L - Glad to be of service 😬 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted August 23, 2013 Share Posted August 23, 2013 Do note that the thermostat can only be fitted ina certain rotationall position due to the housing moulding ..... so check which way is up as you remove it .... best to get the 3mm hole at the top of the flange. Link to comment Share on other sites More sharing options...
revilla Posted August 23, 2013 Author Share Posted August 23, 2013 SM25T points duly noted thank you. Link to comment Share on other sites More sharing options...
garybee Posted August 23, 2013 Share Posted August 23, 2013 Quoting revilla: My main question though still stands - and garybee I totally take your point that the temperature sensor is not very useful if water isn't circulating - does anyone have any idea how to tell how long it is safe to keep running the engine trying to get it to circulate without running the risk of damaging it? Obviously it needs to run up to and beyond the normal thermostat opening point before you know you've got a problem, at which point if things aren't circulating you could already have some very hot spots in the head. 😬 I don't agree that it necessarily needs to run up to thermostat opening temp before an issue becomes apparent. The bypass hose should have coolant flow all the time. If this isn't getting hot (or starts to get cooler during running) then you're not getting flow. Forgot to put this in my previous post...sorry. Link to comment Share on other sites More sharing options...
revilla Posted August 23, 2013 Author Share Posted August 23, 2013 The bypass hoses were very hot. The heater matrix was fully up to temperature. I had flow everywhere except for through the radiator. Link to comment Share on other sites More sharing options...
garybee Posted August 23, 2013 Share Posted August 23, 2013 Quoting revilla: The bypass hoses were very hot. The heater matrix was fully up to temperature. I had flow everywhere except for through the radiator. Ah, that's a lot better then. In which case your temp sensor should be a good reflection of the coolant in the head. I think if the temp raised by more than about 5 deg above the fan 'cutting in' point you can be pretty sure coolant isn't flowing properly. You could always trip the fan manually and check to see if the temp drops (so long as you're above 'stat opening temp). Might mean you get to stop it a bit sooner. Link to comment Share on other sites More sharing options...
jj48 Posted August 23, 2013 Share Posted August 23, 2013 Hi Revilla-YHM Richard Link to comment Share on other sites More sharing options...
revilla Posted August 24, 2013 Author Share Posted August 24, 2013 Well what a difference a 3mm hole in the thermostat makes! Got a Quinton Hazell thermostat from halfords, drilled a little hole in the top of the flange. This time I just left the car level, opened the radiator bleed, opened the expansion cap, then filled it slowly from the bleed tee, closing the radiator bleed when it started showing coolant, closing the expansion cap when the tank level was right and closing the bleed tee when it was full. 5.1 litres, job done. Car now cooling fine, and I've sorted the manifold gasket too, so good to go! Thanks for all the comments Edited by - revilla on 24 Aug 2013 20:53:13 Link to comment Share on other sites More sharing options...
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