Engine cools on highway runs but overheats in traffic
08-18-2003, 09:50 PM
#1
AutoX
Thread Starter
Join Date: Aug 2003
Location: Chicago
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
Engine cools on highway runs but overheats in traffic
I have an '87 S4 with Auto tranny (41k miles) and a RMB. The engine runs hot (has overheated twice!) in city driving but runs at normal temps on highway driving at 50mph or more. I live in Chicago so air temps are not too bad. It is getting to the point where I cannot drive it without risking overheating until I get on a highway. I really hope that someone else can help, I am out of ideas!! Here is what I have had done so far..... new water pump, new thermostat (both verified installed correctly and working correctly), 2 new elec cooling fans which work fine. They come on when the car starts no problem.
The cooling fans stay on after the engine is turned off when it runs hot until the temperature reduces to the acceptable level. The belly pan and front spoiler are in place. I have even had the radiator removed and checked for a restriction by flushing it and checking for leaks. Everything seems ok but alas is not!!! Anyone got any ideas???
Thanks
Chris
The cooling fans stay on after the engine is turned off when it runs hot until the temperature reduces to the acceptable level. The belly pan and front spoiler are in place. I have even had the radiator removed and checked for a restriction by flushing it and checking for leaks. Everything seems ok but alas is not!!! Anyone got any ideas???
Thanks
Chris
08-18-2003, 10:25 PM
#2
Nordschleife Master
Two Words - Radiator Cap.
All kidding aside - it seems you have tackeled the major items. Are there any external leaks that are noticeable?. Or, have you seen any water in the oil?.
I would recheck the fluid level once again - remember the heater must be on and engine at running temperature in order for the water to start circulating once the thermo opens.
Reburp the system and check/replace your radiator cap for proper seal.
Hope this helps.
All kidding aside - it seems you have tackeled the major items. Are there any external leaks that are noticeable?. Or, have you seen any water in the oil?.
I would recheck the fluid level once again - remember the heater must be on and engine at running temperature in order for the water to start circulating once the thermo opens.
Reburp the system and check/replace your radiator cap for proper seal.
Hope this helps.
08-18-2003, 10:31 PM
#3
Drifting
Join Date: Jul 2002
Location: Los Angeles, CA
Posts: 3,348
Likes: 0
Received 0 Likes
on
0 Posts
Nope.
No threads about cooling systems on this board.
No ideas here.
https://rennlist.com/forums/showthre...threadid=82513
https://rennlist.com/forums/showthre...threadid=83756
No threads about cooling systems on this board.
No ideas here.
https://rennlist.com/forums/showthre...threadid=82513
https://rennlist.com/forums/showthre...threadid=83756
08-18-2003, 10:43 PM
#4
Pro
Join Date: Nov 2001
Location: Walnut Creek, California
Posts: 623
Likes: 0
Received 0 Likes
on
0 Posts
Chris,
One of the only things that you did not mention is if you checked the operation of the cooling flaps on the car. If there is a problem with them and they stay closed, the air flow woould be dramatically less and possibly only highway speeds may give your car some air flow. Check those out to see if they are operating correctly. If you can get them open, you then might want to pull the fuse to them to keep them open.
Rob
One of the only things that you did not mention is if you checked the operation of the cooling flaps on the car. If there is a problem with them and they stay closed, the air flow woould be dramatically less and possibly only highway speeds may give your car some air flow. Check those out to see if they are operating correctly. If you can get them open, you then might want to pull the fuse to them to keep them open.
Rob
08-18-2003, 10:56 PM
#5
Rennlist Member
Join Date: Mar 2003
Location: Nashua, NH
Posts: 4,328
Likes: 0
Received 0 Likes
on
0 Posts
Chris,
First, get down on your hands and knees in front of the car and make sure the air intake is not blocked by the ducts coming loose. If it is, secure the ducts out of the way of the air flow with zip ties temporarily.
Next, remove the fuse from the flaps motor while the flaps are in the full open position.
Take two wires about 12 inches long and take the insulation off the last 1/2 inch on one side and the last 3 inches on the other.
Unscrew the hold down from your Final Output Stage (FOS) for your fans (looks like a heat sink on the passenger's side of your engine in front of the headlight bar) and take the plug off the FOS. Double up the short ends of your wires and stick one into plug 5 and and one into plug 8. Secure them to the plug with tape.
Twist the two long ends together and CAREFULLY secure them to the jumper post between the cap and the body. (remove the black plastic cover). The wire will spark until you get a secure connection so wear rubber gloves.
Your fans are now running at their maximum possible speed.
Go for a drive, get the car warmed up and simulate being in traffic. If your car DOES NOT heat up you've got an air flow problem. If it does, it's NOT air flow.
First, get down on your hands and knees in front of the car and make sure the air intake is not blocked by the ducts coming loose. If it is, secure the ducts out of the way of the air flow with zip ties temporarily.
Next, remove the fuse from the flaps motor while the flaps are in the full open position.
Take two wires about 12 inches long and take the insulation off the last 1/2 inch on one side and the last 3 inches on the other.
Unscrew the hold down from your Final Output Stage (FOS) for your fans (looks like a heat sink on the passenger's side of your engine in front of the headlight bar) and take the plug off the FOS. Double up the short ends of your wires and stick one into plug 5 and and one into plug 8. Secure them to the plug with tape.
Twist the two long ends together and CAREFULLY secure them to the jumper post between the cap and the body. (remove the black plastic cover). The wire will spark until you get a secure connection so wear rubber gloves.
Your fans are now running at their maximum possible speed.
Go for a drive, get the car warmed up and simulate being in traffic. If your car DOES NOT heat up you've got an air flow problem. If it does, it's NOT air flow.
08-20-2003, 01:17 AM
#6
AutoX
Thread Starter
Join Date: Aug 2003
Location: Chicago
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
Firstly thanks for the replies, I really appreciate it. I have forced the flaps to stay open and I did the FOS bypass to force the cooling fans to maximum speed. This was the same speed as I have seen the fans running at when the engine runs very hot. There is no air in the cooling system system for sure so the reburp was not done. I did a test run and the results were the same, the engine ran very hot. One thing I did note was that I had been driving the car each time with the AC on and the AC fan set to the "2" position all the time as it has been pretty hot here in Chicago, so I did another test and turned the AC off. The result was that the engine ran up to the upper white notch in city traffic driving but did not overheat. So I guess the hot AC discharge air is to blame for my air circulation problems. The seal at the rear of the engine is in good shape. Any ideas???
08-20-2003, 02:01 AM
#7
Rennlist Member
Join Date: Mar 2003
Location: Nashua, NH
Posts: 4,328
Likes: 0
Received 0 Likes
on
0 Posts
The part that doesn't seem to fit is that your temperature remains normal at speed and rises in traffic. That's usually a sign of limited air flow. You're actually producing more heat the faster you drive, but the increased air flow compensates.
The air has to be sucked through the condenser AND through the radiator by the cooling fans. Make sure your condenser is not blocked with debris.
You didn't mention replacing the radiator hoses. Check the lower hose and make sure it's not soft. If it colapses with the suction from the water pump it can restrict coolant flow.
Do you have a front spoiler on your car?
The air has to be sucked through the condenser AND through the radiator by the cooling fans. Make sure your condenser is not blocked with debris.
You didn't mention replacing the radiator hoses. Check the lower hose and make sure it's not soft. If it colapses with the suction from the water pump it can restrict coolant flow.
Do you have a front spoiler on your car?
Trending Topics
08-20-2003, 02:23 AM
#8
AutoX
Thread Starter
Join Date: Aug 2003
Location: Chicago
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
Ernest:
I agree that it makes no sense but it is what it is and it is driving me #@#@!! Anyway, I have the regular 87 S4 front spoiler and I did check it to make sure that there were no restictions there to air flow. The radiator hoses have been replaced when the water pump was replaced. There is no debris around the condenser.
Thanks
Chris
I agree that it makes no sense but it is what it is and it is driving me #@#@!! Anyway, I have the regular 87 S4 front spoiler and I did check it to make sure that there were no restictions there to air flow. The radiator hoses have been replaced when the water pump was replaced. There is no debris around the condenser.
Thanks
Chris
08-20-2003, 02:48 AM
#9
Rennlist Member
Rennlist Site Sponsor
Check for air recirculation - the hot air going back around into the radiator. The belly pan can really make a difference here.
Check for debris between the A/C condensor and the radiator.
Check for debris between the A/C condensor and the radiator.
08-21-2003, 02:19 PM
#11
Rennlist Member
Join Date: Mar 2003
Location: Nashua, NH
Posts: 4,328
Likes: 0
Received 0 Likes
on
0 Posts
Chris,
When did the problem start? Have you done the water pump, fans, thermostat, hoses and etc. in an effort to solve the problem, or did the problem begin after some of these were done? Did you have the same problem last Summer, or did it begin this Summer?
When did the problem start? Have you done the water pump, fans, thermostat, hoses and etc. in an effort to solve the problem, or did the problem begin after some of these were done? Did you have the same problem last Summer, or did it begin this Summer?
08-21-2003, 03:47 PM
#13
AutoX
Thread Starter
Join Date: Aug 2003
Location: Chicago
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
I have no more progress other than the engine is not overheating BUT I cannot run the AC and it is 93 degrees in Chicago today, so needless to say the shark stayed in the garage today!
When I say "overheat" I mean the red warning light on the temp gauge went off the engine was really, the fans stayed on for quite a while after the engine was shut off.
The belly pan is fine, checked that and there is no debris between the condenser and the radiator.
This problem did not happen last year and the water pump, fans thermostat, hoses etc were replaced in the spring of 2001 more as preventative maintenance than anything else. I like to keep this car in perfect condition, and apart from this issue it is perfect.
Many thanks for your continuing help. By the way, anyone know of anyone in the Chicago area that gets together with their sharks?
Cheers
Chris
When I say "overheat" I mean the red warning light on the temp gauge went off the engine was really, the fans stayed on for quite a while after the engine was shut off.
The belly pan is fine, checked that and there is no debris between the condenser and the radiator.
This problem did not happen last year and the water pump, fans thermostat, hoses etc were replaced in the spring of 2001 more as preventative maintenance than anything else. I like to keep this car in perfect condition, and apart from this issue it is perfect.
Many thanks for your continuing help. By the way, anyone know of anyone in the Chicago area that gets together with their sharks?
Cheers
Chris
08-21-2003, 04:00 PM
#14
Three Wheelin'
Join Date: Jan 2003
Posts: 1,447
Likes: 0
Received 0 Likes
on
0 Posts
With everything that you have replaced......it sounds like something that is not visible is causing the problem.......like water pump impeller slipping somewhat. How's your timing belt tension?? What was your method of testing the water pump after it was on the car?? Maybe you have enough slippage that at low speeds/stop and go driving the coolant flow is not enough, but when are you traveling at a constant higher speed and the engine is spinning at a constant speed there is enough cooland and air flow even with the slipping impeller to cool the engine off. Yes, I am guessing here.......
