Author Topic: Water Temp. (Read 2225 times)

Rabbit TD · « **on:** December 26, 2008, 08:47:55 pm »

I have a question I've been wondering for a good while about. I have noticed for the past three years that my 81 Rabbit 1600 N/A {which is totaly rebuilt and runs perfect} always has a higher reading on the factory temperature gauge when it is colder outside than it does when it's warmer running under the same conditions. You would think it would be the other way around. I have a 180 thermostat and it can be 90 degrees outside and if I am cruising 70 mph I will be at about 30% on the gage. Let the outside temp get down to say 20 degrees and the gauge will be past halfway a little bit if you go to the 195 Degree thermostat the same thing happens but the motor temp changes according to the different thermostat as it should. Motor has never used any water since it was put together 26000 miles ago. The gage showed the same thing on the old motor also which was in reall bad shape, blowby ect. I've changed the sending unit a couple times and still the same thing. My friends toyota does the same thing, it's no big deal and the motor doesn't get anywhere near hot but what makes the gauge show higher just because it's colder outside? Obviously it's the gauge itself but how would outside temp affect it , an ideas. :roll:

theman53 · « **Reply #1 on:** December 27, 2008, 05:42:43 am »

Don't know, but my opinion is that if it is cold then the thermostat doesn't need to be open as much. And when it is it closes really fast. The outside air and it being an open system probably is enough to keep it cool as we are running the heater and such. Just a thought.

Mark(The Miser)UK · « **Reply #2 on:** December 27, 2008, 03:39:53 pm »

My take on this is in mk1 golfs, and all quantum/dasher types. heater is controlled by limiting waterflow rather than mk2 golf air flow. In winter you open flow across water temperature sensor. In summer you shut off water flow from head so sensor runs 'cooler' in stagnant coolant :idea:

Rabbit TD · « **Reply #3 on:** December 27, 2008, 05:55:21 pm »

I kind of go along too with the speed that the thermostat would open and close at but all thermostats more or less work the same on all vehicles I've seen without affecting the gauge readings. But other than that I wouldn't know what it could be either. Like I said before, it isn't even a problem, I'd just like to be able to understand why it reads like that. As far as the heater, it can be completely shut off like in the Spring and it will show a higher reading in the morning than it does in the evening, same road, same speed with it being say 60 in the morning and maby 80 that evening. No big deal, there's bigger problems to solve here. Thanks'

jtanguay · « **Reply #4 on:** December 27, 2008, 07:05:16 pm »

this is indeed a weird phenomenon... i would almost want to put in another mech gauge just to be certain its not the gauge at fault...

rabbitman · « **Reply #5 on:** December 30, 2008, 05:57:06 pm »

My car does the same thing, I have no idea why. In the summer the needle stays mostly in the middle and as soon as it gets cold out in the fall it starts overheating once in a while.

Quote

My take on this is in mk1 golfs, and all quantum/dasher types. heater is controlled by limiting waterflow rather than mk2 golf air flow. In winter you open flow across water temperature sensor. In summer you shut off water flow from head so sensor runs 'cooler' in stagnant coolant

That would make perfect sence except that my heater is on full blast all winter and it still does it from time to time. It'll go for a week or two with normal temps and then out of the blue it'll read 3/4 on the gauge. I've noticed before that if I slow down and let the engine cool a bit then the gauge will go down and stay there. I've wondered since the t-stat is sorta out in the open if the cold air hitting it is enough to keep it closed :!:
I just saw that your talking about way warmer weather than I am so my last statement isn't very relevant.

Rabbit TD · « **Reply #6 on:** December 30, 2008, 06:29:20 pm »

It sounds exactly the same to me and it seems like the colder it gets outside the hotter the gage reads and you can smell antifreeze sometimes when it is super cold so I think the motor is actually running hotter. I know it's not the radiator either beause I tried a diferent one and had the first one done up at a radiator shop and then put it back again, same ***. Thats why I have a 180 thermostat instead of a 195 for winter, crazy ain't it, and it was worse with the 195. My buddy has an old Toyota Tercell that runs perfect and his acts the same way. I just live with it and wonder, 3 years now but it doesnt use any water, you just smell it now & then in the winter. :roll:

jtanguay · « **Reply #7 on:** December 30, 2008, 06:44:03 pm »

like i said.. install an aftermarket sensor & you'll see whats really going on...

the only way i can see it happening is if the t-stat doesn't get enough flow, and is subjected to more cooler air (air flowing around it, just enough to keep it shut)

so the water going to the t-stat is being cooled by the rushing air, and any hot coolant is naturally going to migrate upwards. i suppose this would lead to a situation where the t-stat could remain shut when indeed the temps are in fact rising, but then your water pump would need to be flowing much less coolant than it should.

our systems are leaps better than GM/some other domestics though... put the thermostat at the top most portion of the car :roll: easy to change and bleed system with, but doesn't give out warm/hot air right away when its needed...

Rabbit TD · « **Reply #8 on:** December 30, 2008, 07:57:00 pm »

That is an interesting thought about the thermostat being in the flow of cold air, I never considered that. I wonder if any of the newer diesel vehicles {this is a 81 Rabbit} do this because I think the thermostat stayed in the same place for a good while didn't it, might still be for all I know. That's the most logical thing I can think of though, the Rabbit might just have different airflow characteristics around the thermostat than the other body styles do. It kind of makes me want to rig up a little shield or insulate it some how and see if it makes any difference. Thanks for the thoughts.

rabbitman · « **Reply #9 on:** December 30, 2008, 11:35:52 pm »

Yeah, the other thing is the hose that runs from the T on the front of the head and down the front of the block to the water pump is the one that opens the t-stat so if it can't stay warm the t-stat won't open.
I put a piece of cardboard in front of the engine, it goes from beside the right headlight and covers all but about 8 inches of the rad. As long as I work the engine it gets up to temp otherwise it won't warm up.

Yesterday I went on a 220 Mile round trip drive at mostly -38F-45F and the engine stayed warm untill the ice fog made me have to slow down then it cooled down some.