98' Boxster - Not Accepting Coolant

[BillyJo98]

Good Day,

 

I have a 98’ base 2.5L 5 Speed 986. Recently I replaced the expansion tank (see backstory below) and since replacing the tank, I’ve not been able to get the car to accept more than approximately 3 gallons of coolant. I’m fairly certain that the issue is an air pocket in the system, as I was able to successfully pull 25 lbs. of pressure for upwards of 5+ minutes using the Uview Airlift. I’ve attempted multiple times to get the bubble free first by following the Bentley manual bleeding process.

 

Following this, I’ve tried most every other suggestion on the web. I’ve parked the car on a steep slope and opened the cap (I had quite a few bubbles emerge). I jacked up the back of the car and placed my coolant refill bucket above the tank level. I’ve driven around the block etc. Still, can’t get more than 3 gallons.

 

My question is: Can I fill coolant directly into the radiators? (E.G., remove the bumper, condensers etc. and fill from the top?) Both my engine compartment fan and front radiator fans eventually turn on (car gets up to about 185 degrees). My theory with direct filling radiators is that since each unit houses approximately ¾ to 1 gallon alone, couldn’t I just fill those gaps and then be good to go?

 

On two occasions now I’ve had the tank overflow and leak fluid all over the garage floor.

 

Backstory: About a month ago the car started overheating. I looked at the tank and saw the level was slightly below the “MIN” marking. I topped it off, but continued to have overheating issues. Specifically, the car would get up to about 185 degrees and the blinking light would come on warning of overheating. I purchased a new cap from the dealer and drove around for a day or two with the bleeder valve open. Car continued to overheat. Took it to a mom & pop shop and asked that they flush the coolant. Long story short, they talked me into putting in new coolant and a new thermostat (180 degree), which I agreed to. They called me back and said the car wouldn’t take more than 2.5 gallons and asked for another day to trouble shoot. Next day they texted me and said I needed a new tank (to the tune of $1,300). They said they found pieces of plastic in the tank (I didn’t get to see these pieces). They were also confused by the float in the tank and advised that they couldn’t get this piece out. I had the car brought home on a flat bed.

 

Purchased Uview Airlfit, new coolant, drain plug, crush nut, expansion tank, coolant temp thermostat (the one that goes on the bottom of the tank), etc. . Opened the drain plug and got about 2.0 gallons from under the car. Installed the new expansion tank (took nearly 8 hours). Went to pressure test the system and was shocked to see my new tank full of pink coolant. Released vacuum and emptied coolant from bottom of the car (did this several times) and was quite surprised to end up with slightly less than 4.5 gallons of pink coolant.

 

Meaning, the car that was towed home on the flat bed had close to 4.5 gallons of coolant in the system . . .

 

My theory is that the shop only emptied coolant by opening drain plug and they didn’t actually vacuum everything out. I suspect the coolant I pulled from the new tank came from the radiators.

 

In any case, I now wonder if I’ve fried the new thermostat the shop installed. I purchased a new water pump, belt and 160 degree thermostat and will probably install this coming weekend. I hope not to run into an issue when I go to refill (again). But, in the event that I do, I’m considering trying to put coolant directly into radiators. Wondering how much harm (if any) this might cause.

[JFP in PA]

There is no way to add coolant at the radiators.  The factory evacuates the system with the Uview and draws the coolant in under vacuum, and the car holds around 5 gallons total.

[BillyJo98]

JFP, thanks for the info. I thought for sure this would be possible. But, if that's not the case, then I'm running out of ideas.

 

I'll try evacuating and refilling again this weekend. Given the issues described. Do you think I have a blockage somewhere in the system?

[JFP in PA]

40 minutes ago, BillyJo98 said:

JFP, thanks for the info. I thought for sure this would be possible. But, if that's not the case, then I'm running out of ideas.

 

I'll try evacuating and refilling again this weekend. Given the issues described. Do you think I have a blockage somewhere in the system?

 

First of all, it is nearly impossible to get all of the coolant out of these cars; at best you are going to drain around 85% or so of the total capacity, so with a 5 gallon system, that is about 4 and 1/4 gallons.  Second, with the Uview evacuated down to 25-28 inches of vacuum, there is no air trapped anywhere in the system, even if it is still partially full of coolant, period.  It simply is not possible for any air to remain.  Once one of these cars is refilled under vacuum, there is absolutely no need to open bleeder valves, jack the car up or anything else.  That is the beauty of vacuum refilling.

 

I seriously doubt there is a "blockage", and even if the thermostat was welded shut, there are still by pass coolant passages around it.

[BillyJo98]

JFP,

 

Thanks again for the response. I’ll take another crack at evacuating and filling with the Uview. Must be a user error on my part. Visual inspection of the water pump looked fine. Thermostat is brand-new. Uview pulled appropriate vacuum. Only explanation is user error.

 

I do wonder though if perhaps the new thermostat is fried. Temp got up to around 190 degrees. Twice the tank spewed coolant all over the floor. Each time the temp was around 190 degrees. The first time this happened the radiator fans had engaged. The second time they had not. Should I be concerned?

[JFP in PA]

33 minutes ago, BillyJo98 said:

JFP,

 

Thanks again for the response. I’ll take another crack at evacuating and filling with the Uview. Must be a user error on my part. Visual inspection of the water pump looked fine. Thermostat is brand-new. Uview pulled appropriate vacuum. Only explanation is user error.

 

I do wonder though if perhaps the new thermostat is fried. Temp got up to around 190 degrees. Twice the tank spewed coolant all over the floor. Each time the temp was around 190 degrees. The first time this happened the radiator fans had engaged. The second time they had not. Should I be concerned?

 

First of all, you should be running a 160F thermostat and not the 195 F factory unit.  If you suspect the stat, pull it and get a low temp unit.

 

You also need to know that the dash temp display in these cars are notoriously inaccurate as well as non linear.  The best way to monitor the coolant temp is with a Porsche scan tool like the Durametric system.

[BillyJo98]

Circling back around on this.

 

Replaced the water pump (Porsche part)  and thermostat (Borg Warner 160 degree) this last weekend. As previously mentioned, the existing thermostat was several weeks old (probably less than on hour of actual run-time). Upon inspection, I see lots of scarring inside the metal housing; this might explain some of the silver-colored flakes I found in the coolant? I'm unsure of the age of the water pump. However, the impellor seems to be in good shape and there's no play on the bearing.

 

 The car accepted approximately 4.0 gallons of coolant when refilling with the Uview Airlift. However, I'm still having overheating issues. Several times now I've allowed the car to get up to 180 on the gauge cluster and then crawled under the car to feel the hoses. The hose coming from the thermostat does NOT get hot. The new unit is a Borg Warner 160 degree unit and as such should be opening.

 

To recap: car has a new expansion tank, new water pump, new thermostat, new coolant level sensor and fresh coolant filled via vacuum.

 

On a related note, my front fans no longer come on. As recently as two weeks ago they'd come on when the once the blinking red light on the gauge cluster started to warn of excessive temps. My engine compartment fan comes on around 180. I've turned on the AC to full blast to see if they'd engage, but no luck. I'll test these this coming weekend.

 

Regardless of the fans though, if the thermostat isn't opening and send coolant to the fans, then does it even matter?

 

I've taken the car out for several short drives now. I've filled the tank to the appropriate level (between MIN and MAX). The level hasn't moved at all though over the last several drives.

 

Would an air bubble prohibit the thermostat from opening??? Any idea as to what I should try next?

[JFP in PA]

50 minutes ago, BillyJo98 said:

Circling back around on this.

 

Replaced the water pump (Porsche part)  and thermostat (Borg Warner 160 degree) this last weekend. As previously mentioned, the existing thermostat was several weeks old (probably less than on hour of actual run-time). Upon inspection, I see lots of scarring inside the metal housing; this might explain some of the silver-colored flakes I found in the coolant? I'm unsure of the age of the water pump. However, the impellor seems to be in good shape and there's no play on the bearing.

 

 The car accepted approximately 4.0 gallons of coolant when refilling with the Uview Airlift. However, I'm still having overheating issues. Several times now I've allowed the car to get up to 180 on the gauge cluster and then crawled under the car to feel the hoses. The hose coming from the thermostat does NOT get hot. The new unit is a Borg Warner 160 degree unit and as such should be opening.

 

To recap: car has a new expansion tank, new water pump, new thermostat, new coolant level sensor and fresh coolant filled via vacuum.

 

On a related note, my front fans no longer come on. As recently as two weeks ago they'd come on when the once the blinking red light on the gauge cluster started to warn of excessive temps. My engine compartment fan comes on around 180. I've turned on the AC to full blast to see if they'd engage, but no luck. I'll test these this coming weekend.

 

Regardless of the fans though, if the thermostat isn't opening and send coolant to the fans, then does it even matter?

 

I've taken the car out for several short drives now. I've filled the tank to the appropriate level (between MIN and MAX). The level hasn't moved at all though over the last several drives.

 

Would an air bubble prohibit the thermostat from opening??? Any idea as to what I should try next?

 

Where to begin...…..   If you have scaring inside the water pump housing on the engine, a indication of an incorrect metal impeller pump being used, you may have identified at least part of your problems.  Porsche used ONLY composite impeller pumps to prevent the impeller from gouging up the rear of the pump housing.  Once that has occurred, the next pump may encounter poor or inconsistent coolant circulation because the gap between the new impeller and the engine case is no longer correct.  This, unfortunately, is not a correctable situation, as the engine would need to be removed, disassembled, and the pump housing spray welded to build it back up before machining it back to the correct gap.  And, to be quite blunt, that would cost more than sourcing a used replacement engine.

 

To answer your separate question on air pockets and thermostat performance, yes, an air pocket at the thermostat will prevent it from working correctly as air is a poor media for heat transfer, and the thermostat will not see the actual coolant temp.

 

And to address your blinking coolant light, there are four possible reasons it is lit, and only one is for high coolant temps:

 

Here is the long explanation from the service manual on the flashing coolant light.

"Four functions of the coolant warning light:

1. Engine coolant level too low -- light flashes slowly (0.5 Hz)

2. Engine compartment temperature too high -- light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)

3. Engine coolant temperature too high -- light is lit; pointer on the right

4. Temperature sensor at water outlet faulty -- light flashes rapidly (1 Hz) ; pointer on the right

Note: The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously."

 

You are also not interpreting the coolant flow pattern at the thermostat, the flow is like this:

 

Your thermostat is in the return line from the radiators to the engine, not the out line.

[BillyJo98]

To clarify, I only took a glance at the block once the water pump was removed. My main concern was what the impellor blades would look like. The engine block looked clean and the composite blades also look fine. I can’t speak to what other types of pumps may have been used in the past though, as I don’t have any of the repair history. The scarring I noticed is mainly on inside the thermostat housing, which again was put on the car about 5 weeks ago and has less than an hour of run-time (guestimate).

 

Thank you for sharing the diagram of the thermostat flow. It would make sense based off of the chart that if in fact I do still have a bubble (despite pulling appropriate vacuum with the Airlift) that a closed thermostat would make it nearly impossible to remove the bubble without purging and re-filling again.

[JFP in PA]

29 minutes ago, BillyJo98 said:

To clarify, I only took a glance at the block once the water pump was removed. My main concern was what the impellor blades would look like. The engine block looked clean and the composite blades also look fine. I can’t speak to what other types of pumps may have been used in the past though, as I don’t have any of the repair history. The scarring I noticed is mainly on inside the thermostat housing, which again was put on the car about 5 weeks ago and has less than an hour of run-time (guestimate).

 

Thank you for sharing the diagram of the thermostat flow. It would make sense based off of the chart that if in fact I do still have a bubble (despite pulling appropriate vacuum with the Airlift) that a closed thermostat would make it nearly impossible to remove the bubble without purging and re-filling again.

 

Sorry, but your idea about a close thermostat making impossible to remove air bubbles is not correct.  First of all, the thermostat itself is not actually water tight, it is just an impediment to liquid flow, so even a closed thermostat will allow air to escape.  Second, there is a by pass around the thermostat, which will also facilitate air removal.  All this is one of the beauties of the Uview system, if you pull and sustain a high vacuum (25-27 inches), there simply cannot be any air left in the system.  We have used the Uview tool on Porsches and other makes for years, and never had a problem getting all of the air out of a system.  So if you have evacuated the system correctly to high vacuum, there is no air left anywhere.

[BillyJo98]

JFP, thanks. You keep debunking my "theories" and maybe I'll get a little closer to figuring out what the issue is.

 

So, the Airlift gauge will hold at 25 for as long as I want to leave it there.

 

I'll pay close attention to what blinking patterns the gauge cluster shows and report back. It seems like I've seen patterns 1, 2 and 3 at different points.

[JFP in PA]

5 minutes ago, BillyJo98 said:

JFP, thanks. You keep debunking my "theories" and maybe I'll get a little closer to figuring out what the issue is.

 

So, the Airlift gauge will hold at 25 for as long as I want to leave it there.

 

I'll pay close attention to what blinking patterns the gauge cluster shows and report back. It seems like I've seen patterns 1, 2 and 3 at different points.

You want to get the Uview to at least  25 to 27inches of vacuum and hold it there for five min,. before shutting off the air supply.  Then let the car sit for at least 20 min holding that level of vacuum to be sure you have no leaks in the system, then you can start the refilling process.

[Ahsai]

Perhaps you could remove the thermostat insert from its housing (a special tool is needed but you can use a metal short pipe of the proper size to improvise) and reinstall it and refill with coolant. Then run the engine to 180 and check if the coolant circulates. You can then convince yourself there's no internal coolant restrictions inside the engine.

 

For the cooling fans, check the fuses and the relays.

 

If you want to drain the coolant completely, you can follow these steps (but be very careful not to use too much pressure). 

 

 

 

 

[BillyJo98]

On ‎6‎/‎19‎/‎2019 at 4:10 PM, JFP in PA said:

You want to get the Uview to at least  25 to 27inches of vacuum and hold it there for five min,. before shutting off the air supply.  Then let the car sit for at least 20 min holding that level of vacuum to be sure you have no leaks in the system, then you can start the refilling process.

 

JFP,

 

Question: I have approximately 4.0 gallons of coolant in the car at the moment. Do I need to empty as much as possible before pulling vacuum again per your instructions above?

[JFP in PA]

9 minutes ago, BillyJo98 said:

 

JFP,

 

Question: I have approximately 4.0 gallons of coolant in the car at the moment. Do I need to empty as much as possible before pulling vacuum again per your instructions above?

 

No.  As long as the vacuum device is not touching the liquid level in the surge tank, it will not siphon off coolant.  If the tank is too full, just pull some out with turkey baster and you will be set to go.