twincamtim Posted October 17, 2015 Share Posted October 17, 2015 (2001 Roadsport SV with K series 1.8 120bhp)OK, I have a mystery problem (to me anyway) and wondered if anyone could advise:Radiator fan switch failed mid-July; replaced and worked normally until last week. Replaced the switch again yesterday and the fan worked as expected (only ran the engine up to temp on the drive, not driven). Drove the car for the first time today, did about 10 miles and then the temperature quickly spiked (to 120) followed by it dumping water out of the header tank. It has never done this before. Fan did not work at this point. Does anyone have any ideas? It seems to my simple mind that the failing fan switch is merely a symptom not the cause - has the water pump or thermostat failed?? Link to comment Share on other sites More sharing options...
SM25T Posted October 17, 2015 Share Posted October 17, 2015 If you have an airlock, water can't circulate round the system. If there is air in the top of the radiator, then fan switch won't get hot enough to switch the fan on. Link to comment Share on other sites More sharing options...
SM25T Posted October 17, 2015 Share Posted October 17, 2015 If you have an airlock, the hoses won't all warm up evenly. If you have a heater, I bet it was in there, and released when you turned the heater on yesterday. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 17, 2015 Member Share Posted October 17, 2015 Check it's full up to the highest point in the circuit. Is this easy on yours?Start it and see what happens.Jonathan Link to comment Share on other sites More sharing options...
twincamtim Posted October 20, 2015 Author Share Posted October 20, 2015 I followed the above advice and then ran the engine:The engine steadily warmed up and the temp gauge climbed to 110 - at that point I panicked and switched it off: the heater hoses, the large top hose and the top of the radiator were pretty hot but the bottom of the rad and the large bottom hose were still cold. The radiator fan did not start at any point and the expansion tank didn't leak.Given what SM25T suggests I was thinking of trying the 'hole in the thermostat' approach next....does that make sense? Link to comment Share on other sites More sharing options...
SM25T Posted October 20, 2015 Share Posted October 20, 2015 It will help air get past if you put the hole at the top. You should be able to get the air to the top of the cooling system. Filling very slowly is the key. A bleed tee in the highest heater hose will help too. Link to comment Share on other sites More sharing options...
SM25T Posted October 20, 2015 Share Posted October 20, 2015 Where are you based. Anyone nearby for another pair of eyes on it ? Link to comment Share on other sites More sharing options...
twincamtim Posted October 20, 2015 Author Share Posted October 20, 2015 South Manchester........ Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 21, 2015 Member Share Posted October 21, 2015 How about removing the thermostat and: Running that test again. Checking the thermostat opens at the right temperature... kitchen, pan and thermometer.Jonathan Link to comment Share on other sites More sharing options...
Steve Sheldon Posted October 21, 2015 Share Posted October 21, 2015 My experience is not to put a hole in the thermostat as it will mess up your engine running temperature and your heater system - i have tried it over 2 years - even built a radiator pull up blind to keep the engine temp up on cooler days! The engine is designed to run with steady temperature control - this is also giving the ECU messages re fuelling etc. Best to put a T piece in the highest hose - usually the heater hose and lift the nose of the car up when filling with water. Patience is needed and may take a few times to get all the air out. Link to comment Share on other sites More sharing options...
twincamtim Posted October 21, 2015 Author Share Posted October 21, 2015 It seems sensible to try the advice offered by JK before doing anything else....although the 'holed' thermostat doesn't sound too drastic.G30 on order and hoping for a dry weekend while I tinker.Many thanks for all the advice. I will report back when I have something new to add. Link to comment Share on other sites More sharing options...
SM25T Posted October 21, 2015 Share Posted October 21, 2015 With my car set up as per the LF article (and no airlocks !) it just sits at 80C all day ... including driving in shade temperatures over 41C. The tiny hole in the thermostat allows air through, but not enough volume of water to cause any concerns ! Link to comment Share on other sites More sharing options...
elie boone Posted October 21, 2015 Share Posted October 21, 2015 Strange no one ever tried a banjo in place of the bleed bold on top of the rad, then connect this with a T to the header tank this would prevent any airlock in the rad Link to comment Share on other sites More sharing options...
Steve Sheldon Posted October 21, 2015 Share Posted October 21, 2015 Just to say that it is not about the hole being drastic, it will just mess up your cooling system balance more than you can imagine - I have replaced my holed one with normal and it now works perfectly. I am sure others have had the same problem having followed blatchat advice to make the hole! Link to comment Share on other sites More sharing options...
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