S4 Cooling system performance
#1
Instructor
Thread Starter
S4 Cooling system performance
I have a 1991 S4 auto with about 110,000 miles, in excellent condition overall.
The normal operating temperature on the gauge is just a little below the upper white line except when outside temps require use of the AC. The temp gauge then climbs to midpoint between the upper line and red line. The high temp sensor never alarms but I just don't like it running that high on the gauge.
The thermostat, rear seal, and o-ring were replaced a couple years ago and I think they are good. The coolant has been replaced regularly, at least since I've had it, and is now about 6 months since a flush and change. The coolant reservoir and cap are in good shape, with no leaks anywhere. The cooling fans are working and come on once the temps gauge goes above the upper line.
I have not checked actual temperatures at the coolant hoses to verify the gauge, so the gauge might be off some, but it still looks like there is an inability to cool to the system. The engine temperature is definitely increasing as I can see changes in oil pressure at equivalent rpm as the engine heats up.
My conclusion is the thermostat is apparently wide open, and the engine temperature runs away from the temperature the thermostat would control to.
Is this an indication that the radiator is not capable, for whatever reason, of keeping the system at the correct temperature?
If so, can the radiator be pulled and cleaned? I've done this before on other vintage cars and a radiator shop can do a much better job of cleaning a radiator and putting it back in good shape than I can with it in the car. Or is a new radiator required?
I don't think water wetter additive is a problem solver in this case, no need to offer that advice.
Thanks in advance
The normal operating temperature on the gauge is just a little below the upper white line except when outside temps require use of the AC. The temp gauge then climbs to midpoint between the upper line and red line. The high temp sensor never alarms but I just don't like it running that high on the gauge.
The thermostat, rear seal, and o-ring were replaced a couple years ago and I think they are good. The coolant has been replaced regularly, at least since I've had it, and is now about 6 months since a flush and change. The coolant reservoir and cap are in good shape, with no leaks anywhere. The cooling fans are working and come on once the temps gauge goes above the upper line.
I have not checked actual temperatures at the coolant hoses to verify the gauge, so the gauge might be off some, but it still looks like there is an inability to cool to the system. The engine temperature is definitely increasing as I can see changes in oil pressure at equivalent rpm as the engine heats up.
My conclusion is the thermostat is apparently wide open, and the engine temperature runs away from the temperature the thermostat would control to.
Is this an indication that the radiator is not capable, for whatever reason, of keeping the system at the correct temperature?
If so, can the radiator be pulled and cleaned? I've done this before on other vintage cars and a radiator shop can do a much better job of cleaning a radiator and putting it back in good shape than I can with it in the car. Or is a new radiator required?
I don't think water wetter additive is a problem solver in this case, no need to offer that advice.
Thanks in advance
#2
Rennlist Member
1. Are you sure your oil cooler thermostat is working correctly?
2. What sort of ambient temps are you talking about? The 928 cooling system seems to work quite OK up to about ambient of 39C after that things appear to heat up a bit when you work the motor.
3. The radiator could easily be partially blocked and if so will not work too well. Similarly, make sure the air flow path through the radiator is not obstructed by crud or dusty cements. When was it last cleaned?
4. Cooling is improved by water wettter as it is by using more water [66%] in the mix if cold temps are not a problem. The Red line WW also contains an anti corrosion package which is also important. No point in deploying RLWW unless everything else is in good condition.
5. Presumably your water pump impeller is in good condition.
Regards
Fred
2. What sort of ambient temps are you talking about? The 928 cooling system seems to work quite OK up to about ambient of 39C after that things appear to heat up a bit when you work the motor.
3. The radiator could easily be partially blocked and if so will not work too well. Similarly, make sure the air flow path through the radiator is not obstructed by crud or dusty cements. When was it last cleaned?
4. Cooling is improved by water wettter as it is by using more water [66%] in the mix if cold temps are not a problem. The Red line WW also contains an anti corrosion package which is also important. No point in deploying RLWW unless everything else is in good condition.
5. Presumably your water pump impeller is in good condition.
Regards
Fred
#3
You need to check the temperature with an IR gun. Normal operating temperature is around 180 F and you should see about a 30 degree drop between the Upper and Lower radiator hoses when the engine is at temperature.
Check the Coolant Temp Sender and the wiring and connectors to it. Probably need to replace the sender and if there's corrosion on the wiring, may need to splice in new ones and connectors. The gauges aren't too reliable on these cars. I'd check to make sure the Thermostat was installed correctly (not backwards). Coolant levels are appropriate?
Check the Coolant Temp Sender and the wiring and connectors to it. Probably need to replace the sender and if there's corrosion on the wiring, may need to splice in new ones and connectors. The gauges aren't too reliable on these cars. I'd check to make sure the Thermostat was installed correctly (not backwards). Coolant levels are appropriate?
#4
Drifting
I'm not sure the temp gauge reads accurate. On mine it was running on that upper white line or just below when I acquired the car. I thought that was high but it's at exactly same level having changed rad (the old one let go at one of the side tank seams), coolant, hoses, t-stat (correct 89- onwards one) and that rear seal). I would be happier if gauge read midway just from ergonomics point of view (easier to spot problems), but as it doesn't go higher I just concluded it doesn't read accurate in first place.
I do have IR gun so will check for those very useful readings given by Avar928.
I do have IR gun so will check for those very useful readings given by Avar928.
#5
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
question really is what do those hash marks mean ?? and what is "normal" ? the answer seems to be that the later cars are supposed to read closer to full than empty. Even heard the rumor that someone at Porsche thought it LOOKED better to read higher on the gauge.
I have heard about these "high" readings since S-4s were nearly new cars
I have heard about these "high" readings since S-4s were nearly new cars
#6
Instructor
Thread Starter
Thanks for the feedback.
Thermostat is in correctly.
Radiator is clean externally and visually appears in very good shape, and has been flushed internally in the last few months.
Coolant level is correct.
The issue occurs below 39 C, more like 30. It never gets that hot here in the mountains
Not sure of the water pump condition, it has about 50,000 on it. I suppose circulation could be low. Is there a test for flow from the pump?
I am rounding up an IR gun to check for real temps.
I have heard the same about S4 indicated temperature and have been told by others more knowledgeable than me not to worry.
Maybe I'll just cover the temp gauge with black tape so I can't see it.
Thermostat is in correctly.
Radiator is clean externally and visually appears in very good shape, and has been flushed internally in the last few months.
Coolant level is correct.
The issue occurs below 39 C, more like 30. It never gets that hot here in the mountains
Not sure of the water pump condition, it has about 50,000 on it. I suppose circulation could be low. Is there a test for flow from the pump?
I am rounding up an IR gun to check for real temps.
I have heard the same about S4 indicated temperature and have been told by others more knowledgeable than me not to worry.
Maybe I'll just cover the temp gauge with black tape so I can't see it.
#7
Drifting
My S4 temp needle hovers just below or above the first hash mark most of the time. Left cooling fan cycles on and off after engine warms up. I think the needle when a bit more above the first hash mark on a warm day using the AC. I've wondered if gauge is reading properly. I have an IR gun so I'll do the check Avar928 posted.
Trending Topics
#8
When was the last time the timing belt and water pump were replaced? Check timing belt tension? You probably need to have that serviced already. They're standard replacement items on the car. I personally wouldn't want to leave it alone especially if it's creeping into the red and triggering the cooling fans.
+ EDIT:
Reading Material:
http://members.rennlist.com/pirtle/z...verheating.txt
+ EDIT:
Reading Material:
http://members.rennlist.com/pirtle/z...verheating.txt
Last edited by Avar928; 03-11-2014 at 05:59 PM. Reason: + EDIT - Some links
#9
Race Car
Are the symptoms the same/consistent whether parked or underway?
If the elec fans can cool it when parked, perhaps the cooling flaps aren't functioning....unless I'm wrong about your model year having them, haven't owned an S4 yet!
Is the performance up to par? Vacum leak/lean condition or overly advanced timing could exacerbate heating.
As for level of concern, as the thread matures you may get equal parts 'here are places to buy a radiator', the typical chatter about radiator options, and the view that the 'dash gauge doesn't mean anything get an IR gun and report back', and they all do that (but we know they don't).
And Cap'n S...any chance the prior owner installed a lower temp fan switch and/or thermostat?
If the elec fans can cool it when parked, perhaps the cooling flaps aren't functioning....unless I'm wrong about your model year having them, haven't owned an S4 yet!
Is the performance up to par? Vacum leak/lean condition or overly advanced timing could exacerbate heating.
As for level of concern, as the thread matures you may get equal parts 'here are places to buy a radiator', the typical chatter about radiator options, and the view that the 'dash gauge doesn't mean anything get an IR gun and report back', and they all do that (but we know they don't).
And Cap'n S...any chance the prior owner installed a lower temp fan switch and/or thermostat?