Overheating Problem-Not Solved
08-09-2003, 02:03 AM
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Overheating Problem-Not Solved
With the Devek radiator, the Porsche thermostat cranked open and the rear bypass blocked AND with the stock chips in the car (it took 7 days from purchase to delivery FROM ENGLAND) there's no difference in the overheating issue.
The only difference is that now I KNOW I have a problem. There's NO WAY a car should NOT run cooler with those modifications.
The next step is a leak down test. That heat has to be coming from somewhere.
By the way, the ONLY difference I can feel with the stock chips is a smoother idle. The lumpy "sine wave" is gone! Thanks to John for incredible service.
The only difference is that now I KNOW I have a problem. There's NO WAY a car should NOT run cooler with those modifications.
The next step is a leak down test. That heat has to be coming from somewhere.
By the way, the ONLY difference I can feel with the stock chips is a smoother idle. The lumpy "sine wave" is gone! Thanks to John for incredible service.
08-09-2003, 02:35 AM
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08-09-2003, 02:53 AM
#4
Nordschleife Master
Are you sure the darn guage is accuret?
Are you sure there was something wrong to begin with?
From what it sounds like to me, you've had good fans the whole time. Your ducting seems to be in good order. So no worrys from air flow.
The radaiter might have been partly blocked, but unless your doing some major slow speed pulls, I dought even a fairly large blockage would have caused a problem. The radaitor on my 83 isn't much smaller than that of my fathers F250, or our old GMC with the 454. It's certainly the about same size as my 94 F-150. The engines have way more cooling capasity than they need.
If your aftermarket chips are preforming as advertized, you shouldn't get any knocking, and if you did, it should be very mild. Have you tryed to rap the block as close to the knock sensor as you can get, and see if it retarded the timeing? If your anti-knock sensors we'ren't working as advertized, that could cause your pinging.
Your certain that the water pump was installed correctly, and it is was in good shape?
Lets see, we know you've almost certanly had decent water flow, decent air flow, and under normal cruiseing deffently no knocking.
What does this leave?
The sensor, and the guage that read out. OK, you've already decided that the temo sensor reads high. My next check would be to see if the guage reads high. My suggestion, get a resister of the value that you need for a specific temp reading, put it in the circut insead of the temp sensor, and see if your computer and guage read high. If so, that could be your problem...
I do have a question, do it seem to matter if you have the a/c on or not? In hot weather, when I had the a/c on in my 83, the temp reached the top white line, and then some when I punched it. When I lost the a/c, no matter what the temp outside, it stays right in the middle of the guage, with minor fluctuations when I hit the gas. Is yours similer? To test, you'll have to run around like a moron in hot weather, with the a/c off.
Are you sure there was something wrong to begin with?
From what it sounds like to me, you've had good fans the whole time. Your ducting seems to be in good order. So no worrys from air flow.
The radaiter might have been partly blocked, but unless your doing some major slow speed pulls, I dought even a fairly large blockage would have caused a problem. The radaitor on my 83 isn't much smaller than that of my fathers F250, or our old GMC with the 454. It's certainly the about same size as my 94 F-150. The engines have way more cooling capasity than they need.
If your aftermarket chips are preforming as advertized, you shouldn't get any knocking, and if you did, it should be very mild. Have you tryed to rap the block as close to the knock sensor as you can get, and see if it retarded the timeing? If your anti-knock sensors we'ren't working as advertized, that could cause your pinging.
Your certain that the water pump was installed correctly, and it is was in good shape?
Lets see, we know you've almost certanly had decent water flow, decent air flow, and under normal cruiseing deffently no knocking.
What does this leave?
The sensor, and the guage that read out. OK, you've already decided that the temo sensor reads high. My next check would be to see if the guage reads high. My suggestion, get a resister of the value that you need for a specific temp reading, put it in the circut insead of the temp sensor, and see if your computer and guage read high. If so, that could be your problem...
I do have a question, do it seem to matter if you have the a/c on or not? In hot weather, when I had the a/c on in my 83, the temp reached the top white line, and then some when I punched it. When I lost the a/c, no matter what the temp outside, it stays right in the middle of the guage, with minor fluctuations when I hit the gas. Is yours similer? To test, you'll have to run around like a moron in hot weather, with the a/c off.
08-09-2003, 03:50 AM
#7
Nordschleife Master
Sorry about that, the sensor reads low uh. Have you checked the guage?
I'm sorry, but that is very werid. If you had an overheating problem, it would not stop going up. Instead your system is stabilizeing, and not moveing much up or down, saying, at least to me, that your no where near the max cooling ability of the system. If you were near the max cooling of the system, it would spike up dramaticly when you put a load on the engine, and then fall just as rapidly when you stoped accelerating. But that must be penpered with the fact that the 928 guages are very jumpy. The tempeture, oil, and volt guages cover a narrower range than any other car I've driven, and the seem to be electromagetic, not bimetalic, like some of the new cars. Meaning when there is a small change, it results in a big quick movement of the needle.
Not to mention that if you did too many slow speed, WOT runs, you'd overheat if you were getting into the overheat zone in normal cruiseing, rather than just climbing up high and sitting there, which you seem to indicate isn't happening.
It sounds like a werid sensor, or guage to me. Your t-stat seems to be doing it's job, and the rest of the system seems to have the reserve capasity to hanndle the load.
Very very weird.
I'm sorry, but that is very werid. If you had an overheating problem, it would not stop going up. Instead your system is stabilizeing, and not moveing much up or down, saying, at least to me, that your no where near the max cooling ability of the system. If you were near the max cooling of the system, it would spike up dramaticly when you put a load on the engine, and then fall just as rapidly when you stoped accelerating. But that must be penpered with the fact that the 928 guages are very jumpy. The tempeture, oil, and volt guages cover a narrower range than any other car I've driven, and the seem to be electromagetic, not bimetalic, like some of the new cars. Meaning when there is a small change, it results in a big quick movement of the needle.
Not to mention that if you did too many slow speed, WOT runs, you'd overheat if you were getting into the overheat zone in normal cruiseing, rather than just climbing up high and sitting there, which you seem to indicate isn't happening.
It sounds like a werid sensor, or guage to me. Your t-stat seems to be doing it's job, and the rest of the system seems to have the reserve capasity to hanndle the load.
Very very weird.
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08-09-2003, 04:22 AM
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Ernest, I really think it may be your gauge. Can you buy an inexpensive gauge and run the wires off of the sensor through the side of the hood?, just to see if your gauge correspondes with another. Last I would change the temp sensor, I read where the values may change when the car heats up. Also, can you rig, let's say an american auto makers temp gauge to your car? Again, just to see if it would stay within the normal range. What's your timing set at? Still here with you buddy, Reno
08-09-2003, 06:07 AM
#9
Rennlist Member
Hi Ernest,
Glad you managed the chip install OK, although they didn't fix the overheating problem. Are you going to kep them in the car ?
This has been a very long thread, but did you say that the car has always run hot, or did this start fairly recently ?
As Viribus says, could it be the water pump - impeller slipping on shaft.....
Good luck !
Glad you managed the chip install OK, although they didn't fix the overheating problem. Are you going to kep them in the car ?
This has been a very long thread, but did you say that the car has always run hot, or did this start fairly recently ?
As Viribus says, could it be the water pump - impeller slipping on shaft.....
Good luck !
08-09-2003, 08:29 AM
#10
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Sources of heat in an engine are friction and combustion. Cooling is accomplished with coolant flow, air flow and lubrication. If the problem isn't coolant or air flow, how about oil flow / oil cooling? Does good oil pressure necessarily mean good oil flow?
08-09-2003, 10:51 AM
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The engine generates heat from combustion, mostly in the cylinder head. The amount of heat generated varies greatly with load and speed. The heat is carried away from the cylinder head by a constant flow of coolant, and is then transferred to air flow over the radiator core.
If the amount of heat carried away by airflow is less than the amount generated, the coolant temp increases.
If the temp increases mostly at idle and low speed, the limiting factor is usually airflow.
If the temp increases mostly at highway speeds, the limiting factor is usually coolant flow.
If the temp does not increase, but stays constant under the varying heat loads, then you MUST have excess cooling capacity.
If the controlled, constant coolant temp is higher than desired, the problem almost certainly has to be the controlling device - the thermostat.
In other words, you appear to have perfectly controlled cooling with excess capacity, and probably do not have a cracked head, blown gasket, slipping pump impeller, etc. If you had such a problem, the coolant temp would be lower until the system couldn't keep up, at which point the coolant temp would rise uncontrolably.
We have had a customer who spent several thousand dollars trying to cure an "overheating" problem that turned out to be the temp gauge.
J. C. Whitney used to sell a mechanical coolant temp gauge that used a bulb on a small metal tube. You could loosen the top radiator hose, slip the bulb inside, snug the hose back down on the small metal tube, and get an independent coolant temp reading. That might be worth doing.
If the amount of heat carried away by airflow is less than the amount generated, the coolant temp increases.
If the temp increases mostly at idle and low speed, the limiting factor is usually airflow.
If the temp increases mostly at highway speeds, the limiting factor is usually coolant flow.
If the temp does not increase, but stays constant under the varying heat loads, then you MUST have excess cooling capacity.
If the controlled, constant coolant temp is higher than desired, the problem almost certainly has to be the controlling device - the thermostat.
In other words, you appear to have perfectly controlled cooling with excess capacity, and probably do not have a cracked head, blown gasket, slipping pump impeller, etc. If you had such a problem, the coolant temp would be lower until the system couldn't keep up, at which point the coolant temp would rise uncontrolably.
We have had a customer who spent several thousand dollars trying to cure an "overheating" problem that turned out to be the temp gauge.
J. C. Whitney used to sell a mechanical coolant temp gauge that used a bulb on a small metal tube. You could loosen the top radiator hose, slip the bulb inside, snug the hose back down on the small metal tube, and get an independent coolant temp reading. That might be worth doing.
08-09-2003, 02:57 PM
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Wally,
With all due respect, when the temperature at the crosspipe is consistant with the temperature of the thermistor, which is consistant with the temperature at the gauge AND the temperature that the brain is seeing, it's NOT the gauge. The car slowly heats up to the 100C mark and, so far, has not gone beyond it. (That's the red line). It ONLY does so on the highway, not at idle. It's behaving like a flow problem or an excess heat problem.
Reno,
The car ran normally until I ran a few charity laps on Texas Motor Speedway at speeds from 45 to 90 mph on a hot day. That was the first time I NOTICED the temp gauge high. That was before I changed the water pump/timing belt.
John,
Many thanks for the EXCELLENT service. I'm keeping the chips.
With all due respect, when the temperature at the crosspipe is consistant with the temperature of the thermistor, which is consistant with the temperature at the gauge AND the temperature that the brain is seeing, it's NOT the gauge. The car slowly heats up to the 100C mark and, so far, has not gone beyond it. (That's the red line). It ONLY does so on the highway, not at idle. It's behaving like a flow problem or an excess heat problem.
Reno,
The car ran normally until I ran a few charity laps on Texas Motor Speedway at speeds from 45 to 90 mph on a hot day. That was the first time I NOTICED the temp gauge high. That was before I changed the water pump/timing belt.
John,
Many thanks for the EXCELLENT service. I'm keeping the chips.