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1999 Porsche Boxster overheating issue, Car has 133,000 miles on it.

 

Car overheats when driving on the highway

 

Letting the overheated car sit still and idle after the temperature gauge gets into the above 180° field will cause the temp to fall to just slightly higher than normal.

 

The radiator fans both run and you can feel the air blowing into the radiators and under out of each front end of the car and seems like they are running on high speed. Seems to be a lot of air being drawn into the front bumper opening and being blown out behind the rad. Discharge air seems cooler than I would expect since it is blowing across a 180° radiator. No steam or smell of coolant. Both fans are also able to be activated by my Durametric unit but my durametric unit does not have the ability to activate on low and high only on-off. I do not have the PRO version. Did not check with A/C on/off.

 

The coolant tank is at max mark on tank, no bubbles inside tank when car is running and warmed up.

Not losing coolant at all. New radiator cap replaced last summer cap says motorad germany T25 VW OE P.N. 171121321D. I had it on the car all last summer and did not have any overheating issues. When I bought it it was supposed to be an OEM replacement for my Porsche.The antifreeze was flushed and replaced when I replaced the water pump last year. It was leaking at the seal hole. A new belt was also put on at that time. It did not overheat during the summer months of driving it after all that was done,

 

The oil is full and there is no foam in the oil whatsoever.

 

The interior heater puts out a lot of heat so I assume I am pushing water because I used it to cool car down when it overheated

 

One thing I did notice, I did not hear the engine bay fan run at all. I used to hear this whenever the car was hot when I parked the car. Could it be responsible for the overheating problem by itself? How do I troubleshoot this fan. Tomorrow I am going to drop front bumper cover and clean the radiators.

 

Would like to keep car for a while yet, bought it 4 years ago with 66,000 miles. Wife and I put a new roof on and new seat upholstery, had a clutch installed. So I have a few dollars in it already.

 

Any help would be greatly appreciated, Thanks

 

 

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Check your radiators like you planned.

check your water pump, see if there is seepage.

 

you can remove the serpentine belt and see if it turns freely.

 

lastly, it could be your thermostat sticking.

 

mike

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Definitely recommend a low temp thermostat. If you never cleaned the radiators then you will be shocked and that could help a lot. Most importantly, don’t give up, it is probably something simple!

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I was thinking to see if the fan turns on when idle and running hot. It should blow air from the passenger vent on the side. I think there is a power resistor in the circuit. Also, I think  you should do a flush if none has been performed. It involve the letting the air out where the coolant is added. There is a ring under where the caps are that allows air to be released. This is the first summer for me and I see that the car heats up at stop lights a bit. I also noticed that it ran cooler with an oil change. Oh you need to have the front a bit higher to let the coolant to drain from the front of the car I saw someone say.....good luck.   

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Posted (edited)

Water pump not seeping, it was when I replaced it last year. No clue why I did not replace thermostat at that time. Hindsight says I should have. What actually turns on my front fans? Asking because they both run and shouldn't that indicate the thermostat opened and hot water was sent to the radiator for cooling?  Is there an electric thermostat located at the radiator or are they turned on some other way. The front ones seem to turn on automatically but not sure about the engine fan.

 

I cleaned the radiators and they were really dirty and clogged up with debris. Thanks for that idea, I will definitely put that on my preventive maintenance list. I then drove the car and it still got up to the 200 degrees range, before I stopped driving it, but took a longer time. The front fans run. I did not hear the engine fan run but I was able to jump out relay in the trunk and also was able to turn it on by using durametric unit. What usually turns on the engine bay fan?

 

 

 

I figure the next weekend to change the thermostat and at the same time make sure the water pump I replaced last year does not have any broken parts. I drained and replaced the antifreeze during the pump change.

 

Edited by gene volpe

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The fans are controlled by the DME using sensor signals from coolant or engine compartment sensors,

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Here is my next set of steps to perform this weekend. I am going to change the thermostat. Definitely burp the system as suggested.  I am going to make jumpers with manual switches to override all three of the cooling fans so I can switch them on/auto/off to check results further. This will allow me to understand if one of them is not running correctly. I know the fans up front run but not whether they are on high or low.The durametric unit allows me to start/stop the front fans on and off but not high and low.  I know the engine bay fan runs when I jump it out or use my durametric unit, but not when it should automatically. It used to run every time I turned the car off and it was warm but now even when hot I do not hear it run. 

 

I popped off the relay rack under the left trunk panel to jump out the engine bay fan and jumped from behind but my question is how do I remove the relay without breaking the clips holding it in.

 

Thanks, again

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So I dropped the front clip and disassembled the rad from the cond unit. I could not believe the amount of debris that was between the two of them. I cleaned the radiators which were pretty dirty. After I cleaned them I even took a little tool and straightened any bent fins and cleaned again. I replaced the thermostat (I did not use a low temperature t'stat because it did not have one in it before and it never overheated in the 70,000 miles I drove it the last 3.5 years and now has 133,000 miles) and replaced antifreeze that I drained out. It wasn't too dirty but had some dirt so I decided to replace it with new 50/50 mix. Same amount as I took out since it was full in the tank when I started job.

 

I then let it sit and idle in the driveway and after a while the front fans turned on low speed and after another 10-15 minutes the front fans switched to high speed. A little later the engine fan switched on. So all the fans seemed to work properly but it started toward hot on the gauge so I shut it off because it was getting dark out. 

 

The next morning I did let it run with the burp valve open and after that I did burp it a couple times and then drove it for about 50 miles before the temp went up. It got up to between the 180 and the 250 mark before I turned around. I noticed as I was driving at a lower speed that my temp was dropping. I did not drive it after that because I was concerned after doing damage. Now sitting in garage with front bumper cover still off. 

 

FYI - I changed the water pump last year so it is fairly new. It was leaking at seal. I put about 4 thousand miles on t afterwards with no overheating at all. As an fyi I used wobbler extensions that I got 9 of for $9.99 at Harbor Freight.  It took longer to drain the antifreeze than it did to change the pump. I believe that they worked better than swivel sockets would have.

 

Thought I should mention that I had a new clutch put in earlier this year but did not have any overheating when the job was done until about a month later. Anything they could have done to cause overheating?? They had to remove the exhaust completely to do the clutch.

 

I now have no idea what to check next, do you?

 

Thanks

 

 

 

 

 

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On ‎6‎/‎16‎/‎2019 at 6:49 PM, JFP in PA said:

The fans are controlled by the DME using sensor signals from coolant or engine compartment sensors,

 see my new post about fans running, thanks

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Next thing I would check is the heater valve, 928-574-573-03.  There is a diagnostic procedure for this to see if it is bad, but I don't recall the process off-hand.  Have you also checked temperatures for coolant and oil with Durametric?...just to confirm if things are running hotter than they should. 

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crwarren11 - The car has been garaged because I can't find the issue yet. Really ruins the summer driving a convertible season. Can you tell me the logic why you believe the heater valve may be the problem. I thought the heater valve you described was the valve that closed off the hot water to the heater core when I was on air conditioning. When I turned on the heater the air being put out was hot and when I turned on ac the air was cold.

 

Does anyone think this could have been caused by something when my clutch was replaced? I understand they had to remove and reinstall my exhaust system to do this job. The overheating problem started about 30 days afterwards. 

 

As I mentioned I did notice that when I was at higher speed (55-65) the temp gauge went up past 225 or so and when I was driving back to the garage at lower speeds (35-40) the temperature gauge starting coming back down. The weekend before I let the car sit and idle for about 30 minutes before it went into overheat temperature on the gauge. The front fans came on low then high a short time later and the engine heat fan came on.

 

Have not had the durametric hooked back up to the car to take actual temperature readings as suggested and I am going to try this weekend but I don't know with it going to be 96 degrees and 94 degrees if I will be able to get good readings or not.

 

I replaced the thermostat already. I guess I can pull the water pump off again and look at it if someone thinks that may be an issue. I did replace it last year and drove it a lot with no issues afterwards. If anyone thinks so I can get a new gasket. I replaced it because it was leaking at the weep port.

 

I can work on it but I do not know where to look anymore. I hate to have to ask this question because I figure it will be expensive as heck but does anyone know someone in the Pittsburgh area that could troubleshoot this and give me the correct answer for the right price. 

 

Thanks all.

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13 minutes ago, gene volpe said:

crwarren11 - The car has been garaged because I can't find the issue yet. Really ruins the summer driving a convertible season. Can you tell me the logic why you believe the heater valve may be the problem. I thought the heater valve you described was the valve that closed off the hot water to the heater core when I was on air conditioning. When I turned on the heater the air being put out was hot and when I turned on ac the air was cold.

 

Does anyone think this could have been caused by something when my clutch was replaced? I understand they had to remove and reinstall my exhaust system to do this job. The overheating problem started about 30 days afterwards. 

 

As I mentioned I did notice that when I was at higher speed (55-65) the temp gauge went up past 225 or so and when I was driving back to the garage at lower speeds (35-40) the temperature gauge starting coming back down. The weekend before I let the car sit and idle for about 30 minutes before it went into overheat temperature on the gauge. The front fans came on low then high a short time later and the engine heat fan came on.

 

Have not had the durametric hooked back up to the car to take actual temperature readings as suggested and I am going to try this weekend but I don't know with it going to be 96 degrees and 94 degrees if I will be able to get good readings or not.

 

I replaced the thermostat already. I guess I can pull the water pump off again and look at it if someone thinks that may be an issue. I did replace it last year and drove it a lot with no issues afterwards. If anyone thinks so I can get a new gasket. I replaced it because it was leaking at the weep port.

 

I can work on it but I do not know where to look anymore. I hate to have to ask this question because I figure it will be expensive as heck but does anyone know someone in the Pittsburgh area that could troubleshoot this and give me the correct answer for the right price. 

 

Thanks all.

 

Pressure test the entire cooling system.

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36 minutes ago, JFP in PA said:

 

Pressure test the entire cooling system.

Are you saying to check for leaks? I am never low on fluid and if I start to remove rad cap I can tell it is under good pressure at that time. Every time I drive it and wait for it to cool I am at exactly the same level in the bottle. There is no oil in the water and no water in the oil. and the red light does not come on indicating low on coolant.

Edited by gene volpe
Added comment about light

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38 minutes ago, gene volpe said:

Are you saying to check for leaks? I am never low on fluid and if I start to remove rad cap I can tell it is under good pressure at that time. Every time I drive it and wait for it to cool I am at exactly the same level in the bottle. There is no oil in the water and no water in the oil. and the red light does not come on indicating low on coolant.

 

No, you are looking for an organic reason the engine is overheating, so even though it is not leaking, a pressure test would reveal the presence of mechanical flaws such as cracks, which the early Boxsters were famous for having, and which caused overheating.  I would also be testing the atmosphere above the coolant in the tank for the presence of combustion by products, another indication of possible cracking.

 

You should also have the car scanned with a proper Porsche scan tool to evaluate the actual coolant temperature vs. what the dash gauge displays.  These temperature displays are well known for being both inaccurate and non linear.

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The reason I suggested the heater valve was due to personal experience with it being a culprit in an overheating issue for me previously. On a Tiptronic, though, and I believe it has additional utility on the tips. 

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