78 euro overheating, tried almost everything, need help
09-29-2014, 10:01 AM
#17
Nordschleife Master
So your temp goes up when stationary.
Could another possibility be that when you re-wired the fan, you reversed polarity and now the fan is rotating the 'wrong way' ?
Could another possibility be that when you re-wired the fan, you reversed polarity and now the fan is rotating the 'wrong way' ?
09-29-2014, 05:56 PM
#18
Instructor
Thread Starter
I understand, if my A/C was functional, I wouldn't have pulled the condenser either, so you have to look for another option.
Look, the symptoms are telling you - your problem is "airflow" !!!
When you have airflow, driving at higher speeds or reving the engine at higher RPM, you don't have a problem. If you had a failure or malfunction of one of the components that regulate coolant temp. your problem would be even more evident at higher speeds.
With all due respect to Porsche design geniuses and their testing, the mechanical fan is next to useless at idle or slow, stop and go traffic, on a hot summer day. I am willing to bet, it draws virtually no air through the condenser/radiator sandwich under those conditions.
Your remaining option to provide adequate air flow through your radiator is electric "puller" fan(s), in place of the mechanical fan. I'm sure you're not crazy about this option, considering you've just purchased a new mechanical fan but you may have no choice.
Again, as others have mentioned, make sure the condenser and radiator fins are not clogged up with road junk - leafs, feathers, mud, etc.
Last point, I am not quite clear if your rad temp. sensor, (electric fan switch), is working properly or not. If you have serious overheating problem, your electric fan should be kicking in all the time, whether your A/C is on or not. If your fan isn't coming ON and you've verified both the fan and the switch are working, perhaps it is just your temp. gage that is that is off. However, looking at your temp. readings you've taken, the electric fan should be ON, at least for the last two readings. I believe the stock fan switch is 83 ºC = 181.4 F
Let me/us know, what your eventual fix will be, good luck.
Look, the symptoms are telling you - your problem is "airflow" !!!
When you have airflow, driving at higher speeds or reving the engine at higher RPM, you don't have a problem. If you had a failure or malfunction of one of the components that regulate coolant temp. your problem would be even more evident at higher speeds.
With all due respect to Porsche design geniuses and their testing, the mechanical fan is next to useless at idle or slow, stop and go traffic, on a hot summer day. I am willing to bet, it draws virtually no air through the condenser/radiator sandwich under those conditions.
Your remaining option to provide adequate air flow through your radiator is electric "puller" fan(s), in place of the mechanical fan. I'm sure you're not crazy about this option, considering you've just purchased a new mechanical fan but you may have no choice.
Again, as others have mentioned, make sure the condenser and radiator fins are not clogged up with road junk - leafs, feathers, mud, etc.
Last point, I am not quite clear if your rad temp. sensor, (electric fan switch), is working properly or not. If you have serious overheating problem, your electric fan should be kicking in all the time, whether your A/C is on or not. If your fan isn't coming ON and you've verified both the fan and the switch are working, perhaps it is just your temp. gage that is that is off. However, looking at your temp. readings you've taken, the electric fan should be ON, at least for the last two readings. I believe the stock fan switch is 83 ºC = 181.4 F
Let me/us know, what your eventual fix will be, good luck.
is the aux fan coming on at mid point temp.... this is key and answers the radiator flow question. touching it down there will confirm there is heat in the lower part of the radiator. but the fan needs to turn on, If it isn't, then that could be the issue, or there is flow to get the hot water to the lower part of the radiator. sometimes a flakey waterpump with a loose shaft can do this.
I onece short circuited the radiator with clear hose to see if there was flow at idle. acutally, clear hose out the side of the car from top engine coolant fitting. and pouring water from the garden hose to keep up with the engine demand. its not much at idle, so an easy test. l also pegged open the t-stat to do this.
these cars should run way cool even in hot weather if all is working well. a single electric fan can allow me to run in traffic with no overheating. but,if it stops. the car will overheat.
I onece short circuited the radiator with clear hose to see if there was flow at idle. acutally, clear hose out the side of the car from top engine coolant fitting. and pouring water from the garden hose to keep up with the engine demand. its not much at idle, so an easy test. l also pegged open the t-stat to do this.
these cars should run way cool even in hot weather if all is working well. a single electric fan can allow me to run in traffic with no overheating. but,if it stops. the car will overheat.
I have a viscous fan, so I have not rewired anything. Just disconnected and connected the aux-fan temp sensor which is a termoconrolled switch, i.e. Polarity does not matter.
09-29-2014, 06:20 PM
#19
Nordschleife Master
10-13-2014, 03:40 PM
#20
Instructor
Thread Starter
Hi
A quick update on this matter. I pressure tested the coolingsystem this weekend and it holds pressure just fine without any apperant leaks. Hopefully another good indication towards it not beeing the headgaskets. After reading about airflow issues I did the following test:
I bypassed the aux-fan sensor by connecting the two wires together, I also disconnected the connection to the fan itself. Then I drove the car for a while to get it up to working temp, stopped and let it idle up to 212F on the top radiator hose. At this point I connected the aux-fan and let it idle with the fan running, after doing this for a while it brought the temp back down to the middle of the temp range.
So any conclusions? Could I have bad airflow issues, or is my test only masking over other problems. Anyway the car is now in storage for the winter, bases on my test I think at least I will change to the 75deg termo in the radiator instead of the 92deg.
A quick update on this matter. I pressure tested the coolingsystem this weekend and it holds pressure just fine without any apperant leaks. Hopefully another good indication towards it not beeing the headgaskets. After reading about airflow issues I did the following test:
I bypassed the aux-fan sensor by connecting the two wires together, I also disconnected the connection to the fan itself. Then I drove the car for a while to get it up to working temp, stopped and let it idle up to 212F on the top radiator hose. At this point I connected the aux-fan and let it idle with the fan running, after doing this for a while it brought the temp back down to the middle of the temp range.
So any conclusions? Could I have bad airflow issues, or is my test only masking over other problems. Anyway the car is now in storage for the winter, bases on my test I think at least I will change to the 75deg termo in the radiator instead of the 92deg.
04-12-2015, 01:05 PM
#21
Instructor
Thread Starter
Hi
Summer again in Norway so time to keep searching for what is causing the temps to rise fast at idle.
Some updates are that I have changed to the lower rated 75deg aux fan temp sensor, just for peace of mind until I find the issue. The aux fan now kicks in right before the second white line, and brings the temp down. As soon as it shuts off the temp quickly rises again.
I did a compression test this weekend which gave me 150x6, 160 and 145, hopefully another indication that the headgasket is fine.
My next idea now was to remove the condenser to get better airflow, since the bottow half of the fins seems quite bent. But i did a interesting test which I feel points to it not beeing airflow, while on the highway driving down a hill I put it in neutural thinking I could simulate idle conditions with good airflow. What I saw was the temperature climbing, when I put it in gear againg so the rpms went up the temp drop to normal range again. Any thoughts??
Summer again in Norway so time to keep searching for what is causing the temps to rise fast at idle.
Some updates are that I have changed to the lower rated 75deg aux fan temp sensor, just for peace of mind until I find the issue. The aux fan now kicks in right before the second white line, and brings the temp down. As soon as it shuts off the temp quickly rises again.
I did a compression test this weekend which gave me 150x6, 160 and 145, hopefully another indication that the headgasket is fine.
My next idea now was to remove the condenser to get better airflow, since the bottow half of the fins seems quite bent. But i did a interesting test which I feel points to it not beeing airflow, while on the highway driving down a hill I put it in neutural thinking I could simulate idle conditions with good airflow. What I saw was the temperature climbing, when I put it in gear againg so the rpms went up the temp drop to normal range again. Any thoughts??
04-12-2015, 03:19 PM
#22
Nordschleife Master
... But i did a interesting test which I feel points to it not beeing airflow, while on the highway driving down a hill I put it in neutural thinking I could simulate idle conditions with good airflow. What I saw was the temperature climbing, when I put it in gear againg so the rpms went up the temp drop to normal range again. Any thoughts??
It seems like it's a coolant flow issue. (Captain Obvious, at your service
)I am wondering if the water pump is pumping properly.
You said it was a Porsche pump. When was it put in?
Do you have any idea if it's one of the older ones with the metal impeller?
I'm pretty new to the 928, but the older pumps with the metal impeller have a nasty habit of having the impeller migrate forward, and "eat" the engine block. Once the impeller starts to move, it doesn't flow the coolant anywhere near as well. One of the real experts commented not too long ago about how much damage could occur before coolant flow was affected.
I really hope I'm wrong on this. And if I am, I'm sure someone will point it out.
04-12-2015, 04:11 PM
#23
Instructor
Thread Starter
Hi
The waterpump, cam belt and termostat was replaced last summer to try to fix this problem. There was no difference in the behaviour. I can call the offical Porsche dealer who reparied it to check what type of pump they use, I only have the recit which says the porsche part nr.., I think they might use rebuilt ones.
The waterpump, cam belt and termostat was replaced last summer to try to fix this problem. There was no difference in the behaviour. I can call the offical Porsche dealer who reparied it to check what type of pump they use, I only have the recit which says the porsche part nr.., I think they might use rebuilt ones.
04-28-2015, 06:07 PM
#24
Instructor
Thread Starter
Hi a small update.
I have had a cylinder leakage test performed, and the feedback was that the values were within acceptable range. So at least now I have performed every test imaginable for the head gasket, so I think I can check one item totally off the list.
Values were: Cyl.1: 89%, Cyl.2: 82%, Cyl.3: 90%, Cyl.4: 86%, Cyl.5: 93%, Cyl. 6: 90%, Cyl. 7: 84%, Cyl. 8: 82%.
Means leakdown is 100%-Values.
I have had a cylinder leakage test performed, and the feedback was that the values were within acceptable range. So at least now I have performed every test imaginable for the head gasket, so I think I can check one item totally off the list.
Values were: Cyl.1: 89%, Cyl.2: 82%, Cyl.3: 90%, Cyl.4: 86%, Cyl.5: 93%, Cyl. 6: 90%, Cyl. 7: 84%, Cyl. 8: 82%.
Means leakdown is 100%-Values.
04-28-2015, 07:19 PM
#25
What temperature readings are you getting with an IR thermometer at the sensor, located on the water bridge. Bad electrical harness will give you inaccurate readings.