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Vtx531

01 Boxster Overheating

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Posted (edited)

It has already had the waterpump, thermostat, and coolant temp sensor replaced by local shop (prior to me buying it).

 

It seems like the large hose coming out of the thermostat is not getting hot and not filling with coolant (when the car is warmed up). I put my hand on the hose and it is hot near the thermostat but not further down the hose. Almost feels like it is full of air, I can squeeze it and there is pressure inside but doesn’t feel the same as the other large coolant hose.

 

I tested the thermostat in boiling pot of water and verified it is opening.

 

I can hear the fans running. Fan fuses are good.

 

What should I check for next?

 

 

Edited by Vtx531

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9 hours ago, Vtx531 said:

It has already had the waterpump, thermostat, and coolant temp sensor replaced by local shop (prior to me buying it).

 

It seems like the large hose coming out of the thermostat is not getting hot and not filling with coolant (when the car is warmed up). I put my hand on the hose and it is hot near the thermostat but not further down the hose. Almost feels like it is full of air, I can squeeze it and there is pressure inside but doesn’t feel the same as the other large coolant hose.

 

I tested the thermostat in boiling pot of water and verified it is opening.

 

I can hear the fans running. Fan fuses are good.

 

What should I check for next?

 

 

 

Sounds like trapped air.  Fastest way to correct this is to pull a vacuum above the coolant in the surge tank and get the air out, or open the coolant vent valve and "burp" the system.

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Thanks I already opened the vent valve and drove around and refilled with coolant multiple times but that didnt seem to help.

 

Is that large hose coming out of the thermostat supposed to feel full of coolant and hot when the car is warmed up? Could there be a blockage?

 

I dont really understand and couldnt find a diagram of the plumbing for the cooling system so I don’t know what hoses are what.

 

i am thinking I need to take off all the plastic underbody panels and check fo blockages but hard to imagine that both radiators would be blocked, there should still be some flow I would think.

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34 minutes ago, Vtx531 said:

Thanks I already opened the vent valve and drove around and refilled with coolant multiple times but that didnt seem to help.

 

Is that large hose coming out of the thermostat supposed to feel full of coolant and hot when the car is warmed up? Could there be a blockage?

 

I dont really understand and couldnt find a diagram of the plumbing for the cooling system so I don’t know what hoses are what.

 

i am thinking I need to take off all the plastic underbody panels and check fo blockages but hard to imagine that both radiators would be blocked, there should still be some flow I would think.

 

This should help, it shows how the coolant flows in your car (red is hot out, blue cool returning):

 

spacer.png

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So cooled return fluid goes into the thermostat? Is that the opposite of most vehicles?

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1 minute ago, Vtx531 said:

So cooled return fluid goes into the thermostat? Is that the opposite of most vehicles?

 

Let's just say it is not the most common approach, but it does work well when everything is up to snuff.

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I guess that could explain why that hose going “out” of the thermostat doesnt feel hot.

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4 minutes ago, Vtx531 said:

I guess that could explain why that hose going “out” of the thermostat doesnt feel hot.

 

Correct, it is warm water returning from the radiators.

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Tried refilling again with the burp valve up (with distilled water for now). Still overheating after about 2 miles. The needle sorts of climbs slowly then gets jumpy and goes to the right.

 

Looks like the tank could use more coolant. If I try to remove the cap, steam comes out and then the coolant level rises back up on its own and will overflow if I don’t replace the cap. So unable to put more coolant in.

 

Now that the car has cooled down, I went out to Discover the tank was low and I could remove the cap and it stayed low. So I topped it off again.

 

Do I need to just keep repeating this procedure of warming the car ip and letting it cool and refilling?

 

The videos and writeups I have read about filling the coolant don’t really mention this problem. They make it seem like you can fill it up and drive normally (without overheating) and just keep topping it off over a few days.

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9 minutes ago, Vtx531 said:

Tried refilling again with the burp valve up (with distilled water for now). Still overheating after about 2 miles. The needle sorts of climbs slowly then gets jumpy and goes to the right.

 

Looks like the tank could use more coolant. If I try to remove the cap, steam comes out and then the coolant level rises back up on its own and will overflow if I don’t replace the cap. So unable to put more coolant in.

 

Now that the car has cooled down, I went out to Discover the tank was low and I could remove the cap and it stayed low. So I topped it off again.

 

Do I need to just keep repeating this procedure of warming the car ip and letting it cool and refilling?

 

The videos and writeups I have read about filling the coolant don’t really mention this problem. They make it seem like you can fill it up and drive normally (without overheating) and just keep topping it off over a few days.

 

The recommended way of filling these cars with coolant is under vacuum, it is the way the dealer and any well equipped shop would do it specifically because of these issues.  I would suggest shortcutting all the top off and run it folderol and take it to someone with a Uview vacuum filling system; once connected, it will all be over in about 5 min.

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Posted (edited)

Regarding the vacuum filler: I rented a pressure tester from autozone today. It has quick connect fitting that attaches to the expansion tank. I wonder if I could come up with a fitting from the hardware store that would attach. The U-view looks to be basically a ball valve with some fittings and a length of plastic hose?

May try that later...

 

In the meantime, last night I drove around. Car didn’t overheat but did have steam escaping the cap. The part number ends in -00 so I will order a new cap. I don’t think there should be steam escaping if the car is not overheated. I couldn’t pressure test the cap because none of the adapters fit the cap.

 

Right now I am experimenting with the pressure tester. I pumped the cooling system up to 15 psi and as the pressure increase, the coolant level in the tank decreased. Is that normal?

 

It started loosing pressure slowly but it looks like the pressure is escaping the bleeder valve. The metal pull tab isn’t doing anything because the pressure is causing the valve to pop up automatically. Is that normal?

 

Seems to have leveled off at about 12 psi and not loosing pressure any further. When I let the pressure out, the coolant level comes back up and the bleed valve closes. Upon adding pressure again, the coolant goes down. Looks like the bleed valve starts to open at about 4 psi.

Edited by Vtx531

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11 minutes ago, Vtx531 said:

Regarding the vacuum filler: I rented a pressure tester from autozone today. It has quick connect fitting that attaches to the expansion tank. I wonder if I could come up with a fitting from the hardware store that would attach. The U-view looks to be basically a ball valve with some fittings and a length of plastic hose?

May try that later...

 

In the meantime, last night I drove around. Car didn’t overheat but did have steam escaping the cap. The part number ends in -00 so I will order a new cap. I don’t think there should be steam escaping if the car is not overheated.

 

Right now I am experimenting with the pressure tester. I pumped it up to 15 psi and as the pressure increase, the coolant level in the tank decreased. Is that normal?

 

It started loosing pressure slowly but it looks like the pressure is escaping the bleeder valve. The metal pull tab isn’t doing anything because the pressure is causing the valve to pop up automatically. Is that normal?

 

Seems to have leveled off at about 12 psi and not loosing pressure any further. When I let the pressure out, the coolant level comes back up and the bleed valve closes. Upon adding pressure again, the coolant goes down. Looks like the bleed valve starts to open at about 4 psi.

 

You need an air compressor to operate the Uview and create vacuum.

 

If you pressured the tank and the level dropped, you just proved you have air in the system.  Air is compressible, coolant is not, which is why the level changed.

 

The system should hold pressure at 18 PSIG, if it drops lower, it is leaking.  Bleeder valves are known to do this.

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Thank you for your advice I really appreciate it. So you think there are two issues...

 

1. Air in the system... say I use the vacuum fill method, do I need to completely drain the system first? I would imagine the answer is yes.

 

2. Bleeder valve... I could actually see air bubbles coming out the bleeder valve between the top half and the bottom half where there screws are. What would be the fix for this?

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3 minutes ago, Vtx531 said:

Thank you for your advice I really appreciate it. So you think there are two issues...

 

1. Air in the system... say I use the vacuum fill method, do I need to completely drain the system first? I would imagine the answer is yes.

 

2. Bleeder valve... I could actually see air bubbles coming out the bleeder valve between the top half and the bottom half where there screws are. What would be the fix for this?

 

1.  The answer is no.  As long as the vacuum tool is above the liquid level, it will not pull coolant out.  I would suggest bringing the vacuum level up slowly as the system will "burp" which could splash coolant onto the vacuum unit.

2. The bleeder has O-rings on it that can be replaced, and you can buy a complete new unit as well.  DO NOT use aftermarket pieces, they have proven to be of poor quality.

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The two screws near the leak seemed a bit loose. I tightened up the screws a bit and the leak seems to have stopped and holding pressure.

 

Now to sort out the air in the system...

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Using my makeshift vacuum fill system. When I bring the vacuum pressure up, the coolant level in the expansion tank rises. At about 15”hg the coolant starts getting sucked up the hose. If I release th vacuum, coolant level goes back down to where it started. Is that how it is supposed to work if it is already partially filled?

 

I did it a second time and it did pull in coolant...all the way to the top of the filler neck.

 

Not sure if I did the procedure correctly. It seems like if there was an air pocket in the system that is already filled then the vacuum would just move the air pocket closer to the filler hole with the coolant level rising a corespondent amount. Without actually getting the air pocket out.

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7 minutes ago, Vtx531 said:

Using my makeshift vacuum fill system. When I bring the vacuum pressure up, the coolant level in the expansion tank rises. At about 15”hg the coolant starts getting sucked up the hose. If I release th vacuum, coolant level goes back down to where it started. Is that how it is supposed to work if it is already partially filled?

 

I did it a second time and it did pull in coolant...all the way to the top of the filler neck.

 

Not sure if I did the procedure correctly. It seems like if there was an air pocket in the system that is already filled then the vacuum would just move the air pocket closer to the filler hole with the coolant level rising a corespondent amount. Without actually getting the air pocket out.

 

You need to throttle the vacuum and bring the level up slowly, the system is trying to "burp" and you need to bring the vacuum up in stages so the system can expel the air without pushing the coolant ahead of it.  Ultimately, you should reach 25-27 inches of vacuum when the system is free of air.

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Coolant level still goes down when I pressurize the system so I think that means there is still air? I probably need to drain the whole thing, then pull the vacuum and then refill. I don’t understand how it would work if there is already air trapped.

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Posted (edited)

I was using a hand pump vacuum so the vacuum pressure was definitely coming up SLOWLY. It seemed less like burping and more like drawing up/out the fluid in the tank.

Edited by Vtx531

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1 minute ago, Vtx531 said:

Coolant level still goes down when I pressurize the system so I think that means there is still air? I probably need to drain the whole thing, then pull the vacuum and then refill. I don’t understand how it would work if there is already air trapped.

 

We do this all the time when DIY coolant changes don't work out; it can be done, but you have to raise the vacuum level slowly in stages to allow the air to come out.

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15 minutes ago, Vtx531 said:

I was using a hand pump vacuum so the vacuum pressure was definitely coming up SLOWLY. It seemed less like burping and more like drawing up/out the fluid in the tank.

 

That's because you have a lot of air in the system. Try draining the tank with a turkey baster and then pulling a vacuum SLOWLY...…..

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Drained the tank, then pulled a vacuum. Coolant came up into the empty tank. I did it slowly because it took a few hundred pumps by hand. The coolant started being drawn up the tube when the vacuum reached 21” mg. After refilling (with the vacuum suction), as a test, the coolant level still goes down in the tank when pressure is added. Still air in the system?

 

So...basically same result as before. I could see the two large coolant hoses shrunk down pretty good.

 

Maybe there is still a large air pocket that is causing the coolant level to rise and not “burp”?

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Yes, the air is compressible.  It all depends upon where the air is; if it is in the engine it should come out easily, if it is in the radiators, it will try to push a lot of water ahead of it.

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