Turbocharger Posted January 5, 2014 Share Posted January 5, 2014 Posted in International because this engine is in Defenders and Discos... I have a strange problem with my cooling system, which isn't causing me a problem! I don't use the car very often; usually I'm starting it after a week or two in the garage. The coolant temperature gauge works its way up to 85 degrees or so, then levels out and stays there. So far, so normal. Some time later in the journey (time varies, it was 25mins today but generally seems to be the first time the temperature would drop a little, eg a motorway services or the first long downhill section) the temperature gauge drops to 70degrees. It surges a little, swapping between 70 and 85 degrees in under a second, then within a couple of minutes it settles on 70 degrees and stays there for the rest of the journey. If I restart the car on the same day, or even the following day, it'll come up to 70 degrees and stays there. Concerns: - It could be an airlocking issue? I've swapped the header tank for a different type so that the bleed pipe now vents below the coolant level, but it's not had an effect. - It could be an electrical fault - but why 'fail' to the same temperature, after the same period of time, and then recover a week later? Reassurances: - It's been doing this for two or three years, has been laning, pay&play and lots of road miles incl crossing the Pyrenees, and it's not blown a gasket. - It doesn't use any water. - My IR thermometer shows 83ish degrees on the aluminium thermostat housing, after a run when the engine's idling and the gauge is showing 70 degrees. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted January 5, 2014 Author Share Posted January 5, 2014 Could it be something to do with the 'bubble ejector' - the black plastic piece just to the right of my hand? (Note that this photo shows the old header tank - I've just swapped it for a similar part with both pipe fittings on the bottom face). Quote Link to comment Share on other sites More sharing options...
Maverik Posted January 5, 2014 Share Posted January 5, 2014 Sounds like your thermostate is goosed... I've just been through a complete faff with mine giving very strange temperatures depending on load even after taking the thermostate out and doing some bench tests which seemed to prove it as ok, I put a replacment one in and all steadied itself out... probably worth a look... Mav Quote Link to comment Share on other sites More sharing options...
pete3000 Posted January 5, 2014 Share Posted January 5, 2014 No I don't think it sounds too unusual? I had a think about it. Engine warms up with thermostat closed and warms to 80 ish (sender is on thermostat housing) then at 82-85 stat opens up circulating water into rest of system rad etc which drops the temp of the water again. once water is circulating in full system viscous fan is cooling to 70 or less on a cold day unless the stat closes again. when closes again water will be warmer close to engine. The luxury you have over mine is a gauge which works I have boggo lr part which always sits around upper 2/3rds offull deflection edit: if it doesn't always goes to 85 first then drop to 70 then I'd go with mav with a stick thermostat, although i'd go with sticking open, which isn't as bad as sticking closed. Quote Link to comment Share on other sites More sharing options...
simonb Posted January 5, 2014 Share Posted January 5, 2014 If the IR thermometer says 83, I would say its electrical on the gauge. The ejector in your 2nd post is really just a glorified T piece to allow the rad and thermostat housing to bleed a little coolant back to the header tank to prevent air bubbles forming. Check its not sludged up. If it was, then the thermostat housing is more likely to collect bubbles as that's the high point, if that happens the thermostat won't be fully immersed and will open late leading to overheating. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted January 5, 2014 Author Share Posted January 5, 2014 Forgot to add, I'm now on my third thermostat in four or five years, I've replaced them with genuine units when I've had a burst of enthusiasm to tackle the issue. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted January 5, 2014 Share Posted January 5, 2014 I'd be looking at the gauge and sender... Your stat shouldnt open however untill 88 degrees C. Quote Link to comment Share on other sites More sharing options...
DaveSIIA Posted January 7, 2014 Share Posted January 7, 2014 I've had to unblock the "bubble ejector" a couple of times on my 300Tdi, so would check both branches (& pipes) are clear - no cost quick check. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted January 12, 2014 Author Share Posted January 12, 2014 Had another look at it today, checked that the bubble ejector was clear and ran another wire from the sender to the gauge. I drove up a steep hill away from home, and the gauge settled to 82 degrees within three miles- at this stage the top of the radiator was 70 degrees on the header tank, and 55 degrees on the bottom tank (using an IR thermometer). Three miles on, the gauge showed 82 degrees, and the rad was 80 & 65 degrees. Then, after ten miles or so, the gauge started to waver (see video) in a way which looks like an electrical fault. Within five minutes the gauge settled on 70 degrees, with the rad at 75 / 55 degrees. Looking at the video it does look like an electrical fault - is this how senders fail? Does anyone have the same Racetech gauge and sender, and could measure the resistance across it when hot and cold for me? Quote Link to comment Share on other sites More sharing options...
dailysleaze Posted January 12, 2014 Share Posted January 12, 2014 My standard gauge had the same erratic behaviour due to a dodgy connection at the sender Quote Link to comment Share on other sites More sharing options...
mmgemini Posted January 12, 2014 Share Posted January 12, 2014 I don't think you have a problem. You're just watching the gauge too much. With my 300Tdi with a very accurate coolant gauge in cold weather I can see when the thermostat opens and closes. When in Africa the gauge would rise when climbing a bank/ hill, only to drop below the "normal" 86.4 deg C as I descended the bank on the other side. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted January 12, 2014 Author Share Posted January 12, 2014 It definitely shouldn't wiggle like it does in the video though. The problem is that the coolant is hotter (with the IR thermometer) than the gauge shows - so I can't have confidence that it's working properly. It looks electrical, I've run a new wire so the next suspect is the sender. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted January 13, 2014 Share Posted January 13, 2014 It definitely shouldn't wiggle like it does in the video though. The problem is that the coolant is hotter (with the IR thermometer) than the gauge shows - so I can't have confidence that it's working properly. It looks electrical, I've run a new wire so the next suspect is the sender. Yes I would expect that. Now you have to work out which is accurate. The IR thermometer or the gauge Quote Link to comment Share on other sites More sharing options...
2dextas Posted May 16, 2014 Share Posted May 16, 2014 check the viscous fan- i had simelar sympyons in africa on big hills - fitted an exhaust gas temp guage because i had fried several heads - long story(s) - so could watch temps climb as well as rad guauge - fan seemed ok when cool - using handbook test procedure but new unit transfomed everything. Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted May 17, 2014 Share Posted May 17, 2014 Looking at the action of the gauge, the movement is too fast to be driven by the coolant. Looks to be an electrical problem to me. Quote Link to comment Share on other sites More sharing options...
dave88sw Posted May 20, 2014 Share Posted May 20, 2014 Id agree with the above, the needle is moving far too fast to be temp, it looks electrical, most likely to be the sender but could be the gauge itself. Quote Link to comment Share on other sites More sharing options...
Jamie_grieve Posted May 20, 2014 Share Posted May 20, 2014 I think there isn't much of a problem either, you're just seeing the thermostat working. Keep checking your mouth temperature with the IR thermometer and remember the rubber hoses and radiator have a different emissivity than the thermostat housing so will read higher. The thermostat housing temp should be very close to what the thermostat opens at. The IR thermometer will start to read high when it's been exposed to hot temperatures for a bit. Remember it reads in an elipse that gets larger the further away from the object. To check the thermostat housing you need to be less than 4" 100mm away from it. If you have any doubts and the temperature goes below 80 I'd change the thermostat as it's supposed to maintain a constant temperature. I thought it was supposed to be 88C? 70 - 80's too cold Id say and will lead to glazed bores and premature wear. 300Tdi's don't like getting hot and will warp the head quite significantly if they do. Quote Link to comment Share on other sites More sharing options...
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