Running Cold !!

The car should run at pretty much the same temperature whatever the weather. The whole point of the Stat is to regulate the amount of water that goes to the radiator taking account of the cooling that its providing & what's needed.

Symptoms are consistent with an old thermostat with a weak spring (so it won't close)

I'd put the same spec stat in it as came out. The thing you might also pay attention to though (which is not controlled by a stat) is the oil temperature. If it won't come up then a piece of foam in the left hand air duct may help.

 

I agree with the advice to use same spec and searching here looks like 75C.

I had the same problem. Not warming up during the winter. Weak spring not closing completely and also not opening up completely.

If you search here there are many posts about the thermostat. I was most impressed by Birdman's post. In the end I had my water pump rebuilt and at the same time went with the VW thermostat. It was about $10 US and fixed the running cold problem.

 

+ 1 on blanking off the oil cooler somewhat; I had a 500 kms trip last december in the eastern part of France, outside temperature was about - 2°c all day long, and on the highway the oil temperature did not climb above 60°, which is a bit too cold.
You want it to be at about 75°c at normal cruising speed .

Rgds

 

To each his own but there are a lot of folks in the US that have overheating issues. Once you hit 88*C here it is difficult for these cars to maintain that temp. I run a 74*C in my 77 and it runs all day in any temperature at 74* and my fans never turn on. Oil temp. also runs at around 74*. In the winter all I do is stick a sponge in the oil intake duct and it will run at normal temp.

 

Just because it shuts in a pan of water doesn't mean it will when faced with the pressure from the water pump. From what you describe, the spring is almost certainly weak & as discussed I would put the 74 degree Stat in it if that's OEM spec & then look to manage engine oil temperature as needed. Its at least as important that the oil gets up to operating temperature I think.

 

TRUE --- very important distinction

 

With my car there is a fair degree of inconvenience to remove the thermostat. If I actually had it out of the car I would replace it with a new one without thinking twice just on general principles.

 

If overheating isn't an issue in the first place the running the engine slightly hotter shouldn't be a problem. But by raising the temperatur you would have less of a buffer on a real hot day.

 

Important to remember the main purpose of the cooling system is not to cool but to ensure the correct operating temperature range at all times.

 

I had a similar situation to Steven King when i realigned the oil cooler duct with the oil cooler radiator it instantly gave the car a lower running temperature, having imported my car from the UK i figure that the previous owner has shifted the oil duct slightly away from the oil cooler radiator in order to take it out on cold days. So shift the oil cooler vent slightly away from the radiator or as Steve says "stick a sponge in the intake" this will warm it up.

 

Yes, and if the optimal temperatur range is between the original termostat valve opening and the fans kicking in, then he is all good.

 

Iain, the pump does not pressurise the system it merely circulates the water. Pressure is a result of increased temperature in a sealed system. This is why most falsely think that any air trapped in the system will be forced out by the pump..it doesnt have that capability

The thermostat in my opinion appaers to be working properly, its function is to regulate the temperature of the water in the system at cold start and under normal driving conditions. Driving along the road with -4 (chill possibly -10) the radiator is cooiling the water too quickly. I would suggest blanking off part of the radiator to reduce the heat exchange, how much? thats the difficult bit.



Tony

 

Ohh i agree but i did say "part"!!

Air in the system will only affect flow around the system, nothing else!

Cheers

Tony

we have a slight idea what you are experiencing weather wise as we are getting a cold blast from your direction at the moment

 

As I understand it, the cooling capacity of the air at say -10 is little different from that 0f air at say +25. A given volume of air through the rad is going to strip roughly the same amount of heat from the coolant (which is at +70-80) whatever the air temperature. So external air temperature can be a bit of a red herring.

What matters is that the Stat opens correctly but then that the spring is strong enough to close it again. If it isn't then that's when it opens too far or stays open too long & so the thing runs too cold.

Hence a properly working thermostat + a radiator with more than sufficient cooling capacity should result in a constant water temperature pretty much regardless of the weather (within usual limits) and also regardless of how hard you drive the thing

I also would have though that by definition a water pump creates positive pressure in front of it (and negative pressure behind it)

 

Iain
The difference between radiator average water temperature and the temperature of the cooling air is the reason why we get the transfer of heat.

25C coolant, 25C air no heat transfer, 90C coolant, 0C air = 90C temp difference thus heat exchange takes place!!

Pump creates circulating head both postive and negative with a neutral point in the system. Its purpose is to obviously move a volume of water at a desired flow rate through the radiator to remove heat at a desired rate.

Tony

 

Am aware of the basic principles of the temperature differential, but the point is the size of the differential is not what determines the cooling effect when it is as big as it is in either case, its the volume of air passing through the radiator, the size of the radiator & the flow rate (which is controlled by the thermostat) that do that.

 

Iain
Newton's law of cooling states, the rate of cooling of an object - whether by conduction, convection, or radiation - is approximately proportional to the temperature difference ΔT

 

Indeed so but is it not the case that the appropriate temperature scale for this is in degrees Kelvin, not degrees C (or F)?

i.e. the difference between 10 degrees and 20 degrees is in fact the difference between 283 & 293 degrees - so a fairly small percentage. Hence why, in real terms, the cooling properties of the air at 10 deg is not significantly different to that at 20deg - its going to take about the same amount of heat energy out of the system.

or have I got that "bass ackwards?"

Nonetheless, as long as the thermostat, water pump & radiator are working (and there is basically more cooling capacity than the engine needs) then a working stat should surely be keeping the water temperature at a constant temperature whatever the weather? If it is the case that colder air will cool the thing further/more effectively then the stat is just going to restrict the amount of water that goes out to the rad by not opening so far - that's its job is it not?

I've had 3 failed stats on different cars over the last 3 -5 years and its always been the spring & they always did exactly what the OP described. If you sit in traffic once the car is warm, as soon as you start moving again then the temperature drops to well below normal (because the stat is wide open & the spring won't close it) . It then won't come back up again till you get back into traffic.

 

+1