Frying Pan Posted January 3, 2012 Share Posted January 3, 2012 Took the car for a quick, cold and slippery blat yesterday. First time I've really driven it after servicing it in October Was a cold day (4 deg) and I wasn't driving particularly hard, so was a bit surprised that when I came to a junction I could hear the engine fan running. Tok it even easier form then on, and fan kicked in and out a few times. When I got home, took the bonnet off and the bottom hose was really cool, whilst top hose / heater hoses were boiling. Thought it was either an airlock (I changed the coolant when I serviced it) or a stuck thermostat, but after reading this thread I'm not so sure. Should I worry, or does Bob Corb's post explain things? Bob is local to me, but no longer owns a Se7en (he was busy rebuilding VW Campers last time I heard from him!). I don't remember the fan running before at such low air temps. Guy Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 3, 2012 Share Posted January 3, 2012 well worth jacking up the front of the car as high as possible when trying to bleed the system. Partial draining down to change the anti freeze is a sure fire way of getting an airlock and jacking up seems to be the easiest way of clearing it. The engine needs to be hot and running and the heater on whilst doing this so everything is open and flowing. You'll probably get a sudden huge gurgle of air so stand well back. Link to comment Share on other sites More sharing options...
Frying Pan Posted January 3, 2012 Author Share Posted January 3, 2012 Paul Thanks for the reply - sounds like good advice Link to comment Share on other sites More sharing options...
Unclefester Posted January 4, 2012 Share Posted January 4, 2012 I think one of those bleed units in a heater hose is a good idea, must make this much easier to sort. Link to comment Share on other sites More sharing options...
Frying Pan Posted February 13, 2012 Author Share Posted February 13, 2012 Still concerned about an airlock / non-funtioning stat. Spent another couple of hours today and am convinced I don't have any air in the system. Read loads of posts about bleeding, and have used tips from all of them... Our drive slopes a bit, so parked nose up and took the radiator off the car (pipes attached) and raised to get the air out of the J-pipe to the thermostat, massaged the pipes, used a bleed tee in the top heater hose etc. etc. Fan cuts in and out fine and the bottom hose stays stone cold. Took the car for a drive up the road (why do people look at you funny when you drive a car without a nosecone or bonnet ) and no change. Air temperature is pretty low, but even so, I'd expect something to happen... Supposed to be going for MOT on Saturday so running out of time to try something ☹️ Any ideas Guy Link to comment Share on other sites More sharing options...
CageyH Posted February 13, 2012 Share Posted February 13, 2012 Have you "massaged" the bottom hose while it is getting warm? Does it do it when ticking over? You need to check this. Don't forget, that when it is cold, the radiator will be extremely efficient in cooling at this time of year unless you have some of it blocked off, it will over cool. And will shut the thermostat as it is on the entry to the engine. Leave the car ticking over for a while, and see if the complete cooling system warms up. Ifit does, you don't have a problem with the system, but you need to block the radiator off slightly. Alternatively, fit a PRRT which will overcome the problem, as it creates a radiator bypass loop, and will regulate the temperature better in cold weather. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted February 13, 2012 Share Posted February 13, 2012 Its probably a stuck thermostat although I'm still suspicious that you have an air lock. I'm not sure raising the radiator is the same as jacking up the front of the car as it doesn't do anything for the engine cooling channels. I jack up the front of mine by about 18 inches - the more the better. Stating the bleeding obvious but you did remove the filler cap when running it 'jacked up' 😬 🤔 If it were mine and the jacking procedure didn't work, I'd drain all the water out (if its fresh antifreeze, catch it in a bucket to reuse it) and then refill carefully. Link to comment Share on other sites More sharing options...
Johnty Lyons Posted February 13, 2012 Share Posted February 13, 2012 It's not a stuck stat its a typical K situation the rad is working so well its only letting a little cold water in via the bottom hose [thats why your rad is boiling at top [where fan sw is]] and ice cold at bottom. During winter driving in these conditions I block off the bottom haff of rad to allow more water to circulate Believe me it works.Dont forget the stat is triggered by the by pass hose feeding scalding hot water round top and back of engine this is mixing with ice cold water from bottom hose causing the stat to cycle Give the por thing a braek and increase the temp of water slightly by blocking off your huge [for these conditions] heat exchanger. 😬 Link to comment Share on other sites More sharing options...
Bio Posted February 13, 2012 Share Posted February 13, 2012 Is your car a K series 🤔. Is the stat mounted on the engine block at the pump / hose connection 🤔 Caterham now supply a 74 deg stat with a 3.0mm hole with widget. With no airlocks and a working stat when warmed up the bottom hose should be hot too. With the 74 stat instead of the original 88 the stat should open and allow circulation before the fan starts up (if the fan is controlled by a rad sensor) . Link to comment Share on other sites More sharing options...
Frying Pan Posted February 13, 2012 Author Share Posted February 13, 2012 Thanks for the responses all I'd massaged the hoses, coolant coming out of all the right places when I undo stuff (bleed T, radiator bleed etc.). Having read more and spoken to Bob Corb this evening, I think I'm OK. His explanation agreed with what Johnty wrote; it's doing what it should. Link to comment Share on other sites More sharing options...
charlie_pank Posted February 14, 2012 Share Posted February 14, 2012 Drill a 3mm bypass hole in the thermostat perhaps? Link to comment Share on other sites More sharing options...
CageyH Posted February 14, 2012 Share Posted February 14, 2012 As I said before, check the bottom hose with the car on the drive, with the engine running. If the bottom hose stays cold, you have a problem that needs to be fixed. Link to comment Share on other sites More sharing options...
Johnty Lyons Posted February 14, 2012 Share Posted February 14, 2012 In the situation Cagey describes I agree completly No air passsing through rad whole system should warm up nicely Fan should cut in and out and temp should stablise. That is however not the situation I understood you posted, which is the Sit Rep I refered too. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 14, 2012 Member Share Posted February 14, 2012 Quoting Johnty Lyons: During winter driving in these conditions I block off the bottom haff of rad to allow more water to circulate Is that just blocking the airflow through the bottom half with an external baffle, or something cleverer? Thanks Jonathan Link to comment Share on other sites More sharing options...
Frying Pan Posted February 14, 2012 Author Share Posted February 14, 2012 Quoting Johnty Lyons: In the situation Cagey describes I agree completly No air passsing through rad whole system should warm up nicely Fan should cut in and out and temp should stablise. That is however not the situation I understood you posted, which is the Sit Rep I refered too. Johnty -after leaving the car to idle for five minutes or so, top hose is really hot, as are heater / bypass hoses. Bottom half of rad warming and the J hose was really still quite cool but maybe not stone cold. Once the fan had run, it was really cold. How warm should the bottom hose be? The top hose was really too hot to hold - the bottom hose is always going to be colder, but how cold? Will idling in cold weather allow the stat to open fully? Another trawl of the archives has revealed another thing to check - there is a ball valve in the head behind the small pipe from the expansion tank. Link to comment Share on other sites More sharing options...
Bio Posted February 14, 2012 Share Posted February 14, 2012 Have just had this very problem.....At idle the bottom hose and bottom half of the rad should be nearly as warm as the top. If the stat does not open you will get very little circulation. The old stat removed and found to be defective did not have a hole in the flange and was rated at 88 degrees. The new stat supplied by Caterham was 74 degrees and had a hole in the flange partially obstructed by a plastic widget. John Link to comment Share on other sites More sharing options...
CageyH Posted February 15, 2012 Share Posted February 15, 2012 If it were my car, I would drop the stat out and replace it. At the very least, test the stat. It sounds like it has failed or is sticky. It will cost you a few quid and a couple of hours. Leaving it could cost you much more time and money. Edited for stoopid iPhone auto-corrections correction. Edited by - CageyH on 15 Feb 2012 20:13:38 Link to comment Share on other sites More sharing options...
Frying Pan Posted February 15, 2012 Author Share Posted February 15, 2012 Thanks Is this the right one? Link to comment Share on other sites More sharing options...
mav Posted February 15, 2012 Share Posted February 15, 2012 You can use that one or the htk605 I think it is in halfords which is 82O. Link to comment Share on other sites More sharing options...
Johnty Lyons Posted February 15, 2012 Share Posted February 15, 2012 Johnty -after leaving the car to idle for five minutes or so, top hose is really hot, as are heater / bypass hoses. Bottom half of rad warming and the J hose was really still quite cool but maybe not stone cold. Once the fan had run, it was really cold. How warm should the bottom hose be? The top hose was really too hot to hold - the bottom hose is always going to be colder, but how cold? Will idling in cold weather allow the stat to open fully? When stat is fully open on your drive the bottom hose should be uncomfortable to grasp. On the blocking of rad question[ I have a triple pass race rad and a Laminova] I use a piece of card in depth of winter blocking off up to half of Rad wedged in place Assists rapid warm up and steady running temps I alo have a dry sump with large oil capacity The Kidney tank s behind the rad so is lagged to retain heat. Link to comment Share on other sites More sharing options...
Wrightpayne Posted February 15, 2012 Share Posted February 15, 2012 I have a k and have used the following procedure many times without problem and no jacking up required. My T stat has hole drilled in it and I have the STD copper core rad. Remove the Allen plug on the top of the rad and header cap. Disconnect the top heater hose (or bypass loop if no heater). Connect an old bit of hose to the heater and hold both up. Put a funnel into one the heater hose or temp hose you've fitted and fill slowly. After each jug full give the bottom hose a squeeze. Keep going slowly until water ouzes out of rad - replace Allen plug. Keep filling until header tank starts to fill an put cap on. Keep going until heater hoses overflow then quickly reconnect & tighten clip. Remove header cap an top up to mark. I have now removed the heater and have a bleed tee so simply put the funnel into this and fill. Regards ian Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 15, 2012 Member Share Posted February 15, 2012 Thanks for the blanking advice, Johnty Jonathan Link to comment Share on other sites More sharing options...
Frying Pan Posted February 17, 2012 Author Share Posted February 17, 2012 We have progress (but possibly another problem ☹️) Drained the system down, took the thermostat housing off, removed the thermostat and tested it in a saucepan (SWMBO loved that ) for a few cycles. Opened and closed fine. Tested the new thermostat and that was also good. Decided I might as well fit the new one, so drilled a 3mm hole in it. Must remember to buy some new sharp drill bits, as I broke one, and got the other red hot before it went through... Fitted the new thermostat in the housing and refitted housing and pipes. Refilled, nice and slowly. Lots more gurgling than before Started car and let it idle. No leaks, and top hose / bypass loop came up to temperature. When stat is fully open on your drive the bottom hose should be uncomfortable to grasp. It was 😬 Fan cut in, and bottom hose cooled down nicely. Got a bit of air out of the rad bleed, so I think all is OK Will let it cool down and re-bleed tomorrow. Not sure what the initial problem was, but I suspect there was an air lock despite by efforts. But... I've got a horrible feeling that the bolt holding the thermostat housing and dipstick tube cross threaded as I put it back in ☹️. Was a bugger to get started (can't really see what you're doing, can you) and was then very tight, and won't do up all the way. Tried a few times but with the same result. No sign of a leak whilst idling, but is it likely to be an issue? If so, access to re-tap looks horrible with the engine in the car... Link to comment Share on other sites More sharing options...
CageyH Posted February 18, 2012 Share Posted February 18, 2012 I would try to run a tap down there with the engine in-situ. You may be able to clean the thread up enough, if not you'll need to helicoil it. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted February 18, 2012 Share Posted February 18, 2012 You don't have to use a tap wrench - you can use a small spanner on the end of the tap, or maybe adapt a socket so you can use a 1/4" ratchet ? You are only cleaning a thread in aluminium, so no great torque required. Link to comment Share on other sites More sharing options...
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