samwilliams
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| posted on 22/1/06 at 08:05 PM |
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Think my temperature sensor thing might be not working right
Recently I've been wondering whether the water temperature sensor on my car might not be working properly. It seems to get up to the normal-ish
temperature, but seems to read slightly under what I would expect it to, and also seems to come down noticeably if I go along a bit of dual
carriageway (or similar straight fast road). It doesn't come down to nothing, but will reduce to just above 70, which doesn't seem right.
What would you suggest doing to fix it/check it's working, before I go and replace it?
Thanks
Sam
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britishtrident
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| posted on 22/1/06 at 08:20 PM |
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Thermostat -- either missing or stuck open or somebody has drilled an air bleed hole in it that is too big.
Thermostats generally come in a range of opening temperatures for UK road use they are generally 82 to 88 degrees, but you can get lower and higher
ratedones. Just pick a standard one for you donor ad fit it (remember to get a gasket as well).
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02GF74
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| posted on 22/1/06 at 09:09 PM |
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where are you? if not too far away, pop round to my house I can measure anything you like with my IR termometer.
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samwilliams
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| posted on 22/1/06 at 09:18 PM |
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The thing that was slightly confusing with this is that it was working fine (well, I presume it was working fine before, it just seems to be working
differently now!)
Could it have just come loose? Just to confirm which bit it is, there seems to be two bits with wires going in around the water (I'm really
sorry about my rubbish descriptions!). One has just one wire, the other has two. Which one is it likely to be?!
Thanks
Sam
(by the way, I'm in Bath)
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mark chandler
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| posted on 22/1/06 at 10:15 PM |
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Its the single wire dangling above your alternator in your engine pics.
Car-Engine-002small.jpg
The thermostat should be/is in the housing directly above the sensor, the thermostat is probally knackered or missing.
The cold ambient air makes your radiator more effective which would explain change in readings.
Cheers Mark
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samwilliams
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| posted on 22/1/06 at 11:18 PM |
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quote:
Originally posted by mark chandler
Its the single wire dangling above your alternator in your engine pics.
Car-Engine-002small.jpg
Thanks for that. I forgot I had those pictures there. Just out of interest, what is the one with two wires going in? It's pretty much opposite
the one you mention, and visible on one of the other pictures. I'm gradually working out which bits are which as they go wrong!
Sam
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Chippy
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| posted on 23/1/06 at 12:17 AM |
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If your talking about the one just below the presure cap, I think you will find that it is the fan operating sensor.
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Peteff
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| posted on 23/1/06 at 10:20 AM |
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Your temperature will drop on a blast along a straight road due to more cold air being forced through the radiator. Try blanking half of your radiator
off with some cardboard or something and going for the same run, see if it makes a difference. It's probably just the ambient temperature
causing it to run cooler.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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britishtrident
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| posted on 23/1/06 at 04:33 PM |
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Once warmed up the temperature shouldn't vary much unless you get stuck in traffic.
The thermostat should be able to control the temperature within 5 degrees or so provided you have a by-pass hose connected. You should have by-pass
flow thorough the heater pipe work.
Thermostats just can't work without at least some by-pass flow.
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samwilliams
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| posted on 27/1/06 at 05:57 PM |
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What is the bypass supposed to do? I'm still not convinced that it's right. Today, for example, it had got nicely warmed up to 85C (well,
halfway between the 70 and 100 mark), but then cooled down nearly all the way to 70 after driving along for a bit. This can't be right, can it?
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britishtrident
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| posted on 27/1/06 at 06:31 PM |
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First of all make sure you have a thermostat fitted and check the temperature and is working corectly -- it is the thermostat the controls the
temperature the by-pass improves the mixing and reduces the extreme variations in temperature.
The by pass hose is there to ensure the water flows through all parts of the block whenthe thermostat is closed. If you have no by-pas fitted the
thermostat will remain closed for longer because the water isn't circulating past the thermostat bulb. Eventually the thermostat will open
however if car is running at cruising speed the water in the rad will be over cooled and a slug of very cold water enters the cyliner block -- without
a by-pass this causes a sudden drop in water jacket temperature. A by-pass connection smooths out the extreme variations in temperature and allows the
thermostat to do its job.
All road cars have by pass on some older cars like the BMC Mini it was just an inch long pipe between the water pump body and the cylinder head, on
70s Fords the heater formed the by-pass the heater matrix continually had water flowing through it as air temperature was controled by air blending.
On a Ford either removing the by-pass hose altogether or fitting a Mini/MG style water valve heater can result in poblems.
[Edited on 27/1/06 by britishtrident]
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MikeR
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| posted on 28/1/06 at 11:21 AM |
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i thought the standard thing with the crossflow (my engine) was to plumb the heater feed from the carb inlet direct to the water pump - ie remove the
car heater matrix.
????? have i missed something ???????
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britishtrident
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| posted on 28/1/06 at 04:37 PM |
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Yes thats the by-pass hose.
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stevebubs
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| posted on 28/1/06 at 05:09 PM |
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quote:
Originally posted by samwilliams
What is the bypass supposed to do? I'm still not convinced that it's right. Today, for example, it had got nicely warmed up to 85C (well,
halfway between the 70 and 100 mark), but then cooled down nearly all the way to 70 after driving along for a bit. This can't be right, can it?
In cold weather like this - yes, it can be right....probably means that your radiator is *too* efficient.
As already mentioned, try blocking off half the radiator with some cardboard and see if that makes a difference.
Stephen
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samwilliams
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| posted on 31/1/06 at 05:09 PM |
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Once again, I might be made to look like a fool (I'm getting used to it!). When I was playing with the car this afternoon, I had a closer look
at the temperature guage wire thing, and I was able to push it in a bit. I'll probably be able to tell tomorrow, but I wouldn't be
surprised if that's all the problem was. It might have been cooling the sensor down a lot as I went faster, rather than cooling the engine
itself down!
Never mind. We live and we learn. (I'm hoping that has solved it, because I can cope with looking like an idiot when it makes fixing it that
easy!)
Thanks
Sam
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samwilliams
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| posted on 2/2/06 at 10:18 PM |
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Sadly what I thought might have fixed it hasn't, so I went out and bought a new thermostat today and will be fitting it on saturday. The one
I've got is from halfords and is an HTK600. That's what the man gave me, but I wasn't entirely convinced he really knew what he was
talking about, despite having looked it up on his computer, but I don't suppose any of you would be able to tell me from that if it's
right or wrong? (on the bottom of the thermostat itself it says 88C, M-5, and V-2024 if that helps?)
As for installing it, I've got the haynes manual for the escort, and that's got some information in it, but is there anything else that I
should make sure I do or don't do?
Thanks
Sam
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