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iain Nicholson

Cooling problem

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I recently flushed and replaced the antifreeze in my cooling system. Whilst I was doing this I also inverted the alluminium pipe that the otter switch is mounted to, as mine, an 84 Turbo, was facing upwards, (pointing downwards prevents potential air locks.) After bleeding the system several times (burping the Esprit article very helpfull!)) I took the car for a run, everything was fine, temp gauge read normal throughout the journey, but on returning whilst ticking over, I noticed the rad fans were not switching off, I checked coolant level in the header tank, all fine circulating properly, released the rad bleed screw. again all fine no air trapped, just coolant spilling out as you would expect if the system was bled properly, however I noticed that the bottom radiater hose (off side)was not even warm, where the upper rad pipe (Otter switch near side) was very hot is this normal? Im assuming that a stationary car even with the rad fans on, wouldnt be sufficient to cool water that effectively? plus the rad fans always worked normally switching on and off before the system was flushed. I was certain there were no blockages in the radiator as I flushed this through with a hose pipe before refilling with coolant. The rad fans eventually switch off with the engine switched off, but with the ignition left on, so no thermostatic problem their, plus when I rev the engine with the header tank cap off, there is a healthy flow of water coming out of the return pipe, proving the water pump is fine. Any clues guys??

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:animier: Hi Iain,

First thing I would check is to pop off the wires to the otter swictch and short them together and see if the fans come on - if not, it could be a fuse near the fans. If this is the case, you need to not only replace the fuse, but run a seperate fuse for each fan so this doesn't happen again. It also could be a relay that is out of operation.

If the fans burst into life with the wires touching, then there is insufficient heat getting to the otter switch, or the otter switch is bust.

Did you have the heater turned on full when you burped the car? - common error.

Also, the thermostat could be stuck closed, not letting water circulate past the otter swich.

Some ideas to follow...

Iain

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Hmmm.. from reading the posts it seems Mr.Nicholson's problem isn't fans not switching on, which is the usual thing, but not switching OFF..which is weird. My 1982 Turbo has the otter switch on the offside of the car, the driver's side for us Brits, and that seems to be the input to the radiator. If the otter switch has been installed on the output side of the radiator, and the thermostat has failed shut, then I think it's possible that the engine is getting pretty hot, and the radiator out pipe has got hot enough to operate the otter switch and thus the fans..but it won't do any good because there is no circulation through the radiator because the thermostat has stuck shut. Not a good situation, engine could well overheat catastrophically. Other than that, the fan relay may have failed with the contacts welded together or somehow distorted so that the fans stay on. Do the fans STOP when you disconnect the otter switch? Have you tested the switch itself..take it out and use an ohm meter and a saucepan of water on the stove to check it cycles properly. What else..thinks..I suppose the flushing of the radiator might have dislodged enough muck to block things up now, but unlikely..maybe one of the hoses has collapsed and you thus have no circulation. As I said...weird. Hope my ramblings might help!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I would think there is an air lock of some sort. As you say, the return hose is not likely to be that cold with the inlet hose hot. How difficult is it to return the aluminium pipe holding the otter switch to its original orientation?


S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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Thanks for your imput guys. Appologies, I made the error of stating the offside, when I meant the nearside (passenger side) radiator hose was the cool one! Is it essential to bleed the system with the heater in the hot position? because I may not have done this. In response to the suggestion that there could be a blockage, surely this would cause the car to overheat,? resulting in a higher temp gauge reading,? but this is not the case, the car reaches the same reading on the gauge as before the system was flushed, and doesnt fluctuate from the normal position even after a 20 mile run! Im sure the fan switch and relays are fine as the fans operate only when the car reaches the working temp, they do not come on from cold, and as I mentioned in my post when I turn the engine off they stay on for a minute or so then they turn off when the coolant temp has lowered! I will try and bleed the system again with the heater in the hot position.

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Yes, you should bleed the system with the heater ON...air locks are a hassle with the cooling system, it can take quite a while of fiddling to get it free from air. I'm wondering if you have a failing otter switch..coming on OK but not switching off until a much lower temperature than normal. The fans shouldn't operate at all in normal driving, only when in traffic, going very slowly or stopped. Might be an idea to check it..take it out and connect a test meter across it, then put it in a saucepan of water on the stove and observe what it does as you heat it up and cool it down; a thermometer would help! I had problems with aftermarket otter switches, until I bit the bullet and paid out a silly sum for a Genuine Lotus part..after which, it's been fine for the past 15 years or so!! The fans don't normally come on until significantly above the normal temperature on the gauge..it's 82 degrees, iirc, but that's at the switch itself and the engine will be hotter than that. I can't remember the gauge readings..I have fitted a manual override switch so that I can turn the fans on independently of the otter switch, and thus do away with the "will it, won't it" eye glued to the temp.gauge when in heavy traffic.


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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