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Old 03-18-2017, 03:24 PM   #1
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Help diagnosing cooling system issues

Hi guys,
I'm having some issues with my cooling system and need to run some ideas by you all in the hopes you can help me get to the bottom of this.

Caveats - I've read most of the threads here, and tried quite a few of the recommended steps.

Here's the synopsis.
  • Car was loosing coolant, relatively slowly
  • Noticed coolant in the trunk area and diagnosed problem as a bad overflow tank
  • Replaced overflow tank and all of the spring clamps with worm gear hose clamps
  • Car ran fine afterwards, but I noticed a coolant smell fairly routinely.
  • PO had told me the water pump was an aftermarket unit replaced around 50k miles ago
  • I figured this was as good a time as any, so I replaced the waterpump and thermostat with genuine Porsche parts
  • After doing so, I notice that the heat no longer works
  • After doing some research, I realize the heater core is 'always hot' and that this problem indicates an air pocket in the coolant system
  • I did some further research and realized it might have something to do with a superseded overflow tank cap.
  • I replaced the overflow tank cap with a -04 cap
  • While doing so, I inspected the bleeder valve and all looked ok. I did buy a replacement to have on hand if needed
  • I attempted to manually bleed the system via the bleeder valve, but still had the same symptom regarding the non-functional heater. At this point, the car can no longer make it 'around the block' which is about a 5km track without coolant temperatures reaching 250F
  • I decided to buy the UView vacuum bleeder, drained the coolant and applied vacuum
  • I was only able to draw 15 pounds of vacuum, but the system held vacuum indicating no leaks
  • I refilled the system via the vacuum method and drove the car around the block
  • Heater still does not work, but coolant temperature does not get to 250 (maxes around 230 while driving, and when parked back in my driveway, coolant temp declines to around 200
  • With the car up on ramps, and running, I try to manually 'burp' the coolant system by squeezing the coolant hose on the driver's side of the car at the front of the engine - it's cold, whereas the hose at the thermostat side is hot
  • I think, perhaps the brand new thermostat is bad, or stuck, so I remove/reinstall and inspect it - no obvious problems.
  • I re-do the vacuum fill method, but the vehicle still has no heat

At this point, I'm not sure where to turn next. Is it possible that I have a blockage in the hose leading to the front of the car? Any other thoughts on where I should be looking?

Thanks for your help guys.

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Old 03-18-2017, 03:34 PM   #2
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BTW, its a 2000 Boxster S 6mt
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Old 03-18-2017, 05:55 PM   #3
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Quote:
Originally Posted by PCinDC View Post
Hi guys,
I'm having some issues with my cooling system and need to run some ideas by you all in the hopes you can help me get to the bottom of this.

Caveats - I've read most of the threads here, and tried quite a few of the recommended steps.

Here's the synopsis.
  • Car was loosing coolant, relatively slowly
  • Noticed coolant in the trunk area and diagnosed problem as a bad overflow tank
  • Replaced overflow tank and all of the spring clamps with worm gear hose clamps
  • Car ran fine afterwards, but I noticed a coolant smell fairly routinely.
  • PO had told me the water pump was an aftermarket unit replaced around 50k miles ago
  • I figured this was as good a time as any, so I replaced the waterpump and thermostat with genuine Porsche parts
  • After doing so, I notice that the heat no longer works
  • After doing some research, I realize the heater core is 'always hot' and that this problem indicates an air pocket in the coolant system
  • I did some further research and realized it might have something to do with a superseded overflow tank cap.
  • I replaced the overflow tank cap with a -04 cap
  • While doing so, I inspected the bleeder valve and all looked ok. I did buy a replacement to have on hand if needed
  • I attempted to manually bleed the system via the bleeder valve, but still had the same symptom regarding the non-functional heater. At this point, the car can no longer make it 'around the block' which is about a 5km track without coolant temperatures reaching 250F
  • I decided to buy the UView vacuum bleeder, drained the coolant and applied vacuum
  • I was only able to draw 15 pounds of vacuum, but the system held vacuum indicating no leaks
  • I refilled the system via the vacuum method and drove the car around the block
  • Heater still does not work, but coolant temperature does not get to 250 (maxes around 230 while driving, and when parked back in my driveway, coolant temp declines to around 200
  • With the car up on ramps, and running, I try to manually 'burp' the coolant system by squeezing the coolant hose on the driver's side of the car at the front of the engine - it's cold, whereas the hose at the thermostat side is hot
  • I think, perhaps the brand new thermostat is bad, or stuck, so I remove/reinstall and inspect it - no obvious problems.
  • I re-do the vacuum fill method, but the vehicle still has no heat

At this point, I'm not sure where to turn next. Is it possible that I have a blockage in the hose leading to the front of the car? Any other thoughts on where I should be looking?

Thanks for your help guys.
Did you check the thermostat for opening temperature by immersing it in cold water and then heating the water while monitoring both the water temp and at what point the thermostat opens?
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Old 03-18-2017, 06:06 PM   #4
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I did not, I can try that tomorrow. Is it likely that a brand new genuine porsche thermostat would be DOA?

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Old 03-18-2017, 08:00 PM   #5
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The vacuum process for refilling is rather exacting. Which Instructions did you follow?
I ask because if for example you did not set the heater controls correctly, that may be the cause.
Also if you accidentally let the AirLift tube suck air because it emptied the coolant container.
If you did not completely drain all the coolant before pulling the vacuum.
It is a really tedious process that becomes even more tedious if you fail to follow precisely the correct set of Instructions.
One piece of advice I could not find and maybe JFP would know-
if you get the system almost full - but still have say a quart of coolant left over(- a small airlock somewhere?)
- is it wise to drive with the burp valve open , hoping this will allow the air bubble to purge itself ? Or perhaps run the engine with the rear jacked up to achieve the same objective ?
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Old 03-19-2017, 06:43 AM   #6
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Quote:
Originally Posted by PCinDC View Post
I did not, I can try that tomorrow. Is it likely that a brand new genuine porsche thermostat would be DOA?

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You have a problem, so any component needs to be tested. While not many new thermostats are duff right out of the box, some are. It needs to be tested if for no other reason than to eliminate from the equation.
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Old 03-19-2017, 06:53 AM   #7
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Quote:
Originally Posted by Gelbster View Post
The vacuum process for refilling is rather exacting. Which Instructions did you follow?
I ask because if for example you did not set the heater controls correctly, that may be the cause.
Also if you accidentally let the AirLift tube suck air because it emptied the coolant container.
If you did not completely drain all the coolant before pulling the vacuum.
It is a really tedious process that becomes even more tedious if you fail to follow precisely the correct set of Instructions.
One piece of advice I could not find and maybe JFP would know-
if you get the system almost full - but still have say a quart of coolant left over(- a small airlock somewhere?)
- is it wise to drive with the burp valve open , hoping this will allow the air bubble to purge itself ? Or perhaps run the engine with the rear jacked up to achieve the same objective ?
When you drain these systems, you never get all the old coolant out; at best you are replacing about 85% of the coolant. If the system is tight, and the Uview is used correctly, no other steps are required (e.g.: burping, jacking the car up, etc.). When we do a coolant replacement, we evacuate the system down to 25-26 inches of vacuum, let the car sit for 15-20 minutes to check for tightness, premix the factory coolant with distilled water in a clean 5 gal pail, drop in the Uview hose, and slowly open the fill valve. When the vacuum gauge drops to zero, the system is full and no further steps are required. There is always some excess coolant mix left over, which we put in one of the original coolant gallon bottles, marking it premix with the date, and give it to the owner in case he should ever need it. In reality, we extremely rarely ever need to readjust the coolant level in one of these vehicles once they are recharged, but as the owner paid for the coolant, it is his to take with him/her.
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Old 03-19-2017, 07:03 AM   #8
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Thanks for the replies. I will pull the thermostat off and test it. In terms of the procedure, I did precisely what you describe, but was only able to draw 15 inches of vacuum. Any idea what might cause that? It was able to hold that vacuum.

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Old 03-19-2017, 07:05 AM   #9
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Also, I didn't find the vacuum fill process to be very tedious. Biggest hassle was draining the coolant, after that pretty simple. Only thing stumping me is the vacuum pressure issue noted.

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Old 03-19-2017, 07:10 AM   #10
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Quote:
Originally Posted by PCinDC View Post
Thanks for the replies. In terms of the procedure, I did precisely what you describe, but was only able to draw 15 inches of vacuum. Any idea what might cause that? It was able to hold that vacuum.
If you had checked during your vacuum pulling, , I think you would have found that 15 inches Hg of vacuum was sufficient to collapse the large hoses from the front of the engine. So imho ,that is enough. The problem is maintaining sufficient vacuum throughout the entire process.The risk is the vacuum may decline to the point where air pockets develop.
Unless you measure the coolant carefully, you have no clue if the the system is completely full.Unless you remove all the old coolant you don't know if you are starting from zero or say 2 qts full. In previous threads we have discussed this in detail. An example of what fools like me do is alluded to by JFP. - the residual coolant that is not removed. When I realized that could be an issue, I used the exhaust on a shop vac to blow out all of the old coolant from a "fully drained" system. Try it. You'll get very wet !But you will have empirical evidence that you filled the system with X qts of coolant ,not just some coolant and a giant air pocket.That would be a good basis to continue the diagnosis from ?

Last edited by Gelbster; 03-19-2017 at 07:21 AM.
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Old 03-19-2017, 07:39 AM   #11
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Thanks. I actually did check, and the vacuum had indeed collapsed the hoses at the front of the engine. My next step will be to test the thermostat, part of which includes another drain/fill.

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Old 03-19-2017, 07:47 AM   #12
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When the the old w/p was replaced- do you have the old part- complete? I ask because if the plastic impeller blades had broken, the debris may be plugging the cooling system.The usual blockage area is the heat exchanger.
Quote:
Originally Posted by PCinDC View Post
Thanks. I actually did check, and the vacuum had indeed collapsed the hoses at the front of the engine. My next step will be to test the thermostat, part of which includes another drain/fill.
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Old 03-19-2017, 07:49 AM   #13
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I actually replaced the pump because it was making the telltale metallic whine, which , one morning suddenly went away. I thought I likely did have a disintegrated impeller, but upon removal noted the impeller was intact.

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Old 03-19-2017, 07:50 AM   #14
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How accessible is the heat exchanger for an inspection?

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Old 03-19-2017, 09:36 AM   #15
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Well, some positive signs guys. After driving last night, letting it get up to 230 and parking it, I noticed it came down to 200 in the driveway. I shut it down and opened the bleed valve and let it cool overnight with the bleed valve open. This morning, the coolant level was down, though it hadn't leaked as far as I could tell. Topped it off and drove it around for 20 minutes or so, got up to 180 and stayed there, and heat was working. Going to carefully monitor but the problem may be resolved.

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Old 03-19-2017, 04:04 PM   #16
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PC,
Its OK to run the car for a couple of days with the bleed valve in the open (vertical) position or for at least 2 heat up / cool down cycles to rid the system of any small pockets of air.

One thing of note is that your drive "around the block" is 5km, which is barely long enough for the thermostat to be fully open and all the +/- 20 litres of coolant to circulate and be up to temperature. I've found that if you want ALL the coolant to be at operational temps, it takes possibly double that 5km distance.

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