[Cloud9...68]

[quote name='flash' post='54223' date='Jun 7 2008, 03:28 PM']because the heater core is the highest point in the system - therefore, the air will go there[/quote]

OK, that makes sense, but if I never opened the heater, either during the water pump/thermostat replacement process, or during the subsequent bleeding, I don't understand how air would get in there. But I am holding out hope that maybe during the whole process, I managed to get the opening of the heater and bleeding "out of sync," such that somehow air did get into the heater core, and then I never bled it effectively (or completely), and now these's a bunch of air bubbles big enough to completely shut down the flow of coolant <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" /> somewhere in my system. It sounds far fetched, but it's the best theory I've got at the moment. I'll let you all know how it works out, though as I said, I've got a lot of work to do before I can test this theory.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='smokiemon968' post='54232' date='Jun 7 2008, 04:12 PM']This is something that has worked for me in the past.

If you have access to compressed air,

With the engine cold Insert the air nozzle in the water fill neck

and try and seal the nozzle as good as you can using a shop rag.

Use the compressed air to force the air pockets thru the system.



Then use the usual bleeding procedure.[/quote]

That's exactly the procedure I've used (along with the gravity method, and a few others). I've been using a pressure tester Autozone rents for free, which screws to the reservoir filler, making a tight seal. I then pressurize the system to 12-15 psi using the built-in pump, and crack the bleed screw to let the bubbles out.



It seems to me that an even more effective method would be to replace the bleed screw with a fitting, and attaching a clear hose to the other end of this fitting. Then, pressurize the system, and bleed it like we do our brakes, forcing enough of the coolant through the system and out the hose until I'm sure there's no more air in the system. It wouldn't even waste any coolant, as I could capture it all in a bucket. Of course, this would be done with the heater valve open. But I've never heard of anybody ever using this method, so there either must be some drawback to it, or it's considered overkill. At this point, I'm about ready to wrap my lips around one of the hoses and suck the coolant out, if it would make my car driveable again...

Partial Post: Please Login or Register to read the full post.

[jfrahm]

Your water pump impeller might be spinning on the shaft. My S2 did this, resulting in overheating under load. If you are bleeding the system under pressure it should be fine, any small bubbles will get pushed out once you get the water moving. I bleed the system with the overflow hose in my mouth and a hand over the coolant neck in place of the pressure cap. With my left hand on a wrench on the bleeder screw it's dead easy to blow coolant up into the system. Blow, open bleeder, close bleeder, inhale, blow... after a few iterations put the cap on, take it for a drive with the heat on and give it one good squirt when it's fully warmed up and perhaps on an incline. Really quite easy. However it sounds like you've done the bleeding right, well enough not to overheat anyway.



-Joel.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

I've taken the water pump out, and the impeller is definitely not loose on the shaft.



Your bleeding method is interesting, and definitely unique. My concern is that my air bubbles may be deep in the bowels of my system, so I'm not sure that bleeding just in the vicinity of the bleed screw will do the trick.



But again, I'm a little skeptical that the total shut-down of my coolant flow could be caused by a few air bubbles. I'm still afraid I've overlooked something...

Partial Post: Please Login or Register to read the full post.

[rxter]

This is like watching an episode of ER. Sorry that I am of no help here Cloud. It sounds like you have a garage full of the best Porsche mechanics around.

Partial Post: Please Login or Register to read the full post.

[xrad]

if it's not the pump and not the thermostat, and the system is filled properly, that leaves only the radiator. Once the thermostat cracks open, nothing will restrict flow except a rag in the hose or poorly flowing radiator. Cooling passages are usually pretty big...



or your temp sensor is innacurate...

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='xrad' post='54531' date='Jun 10 2008, 07:31 PM']if it's not the pump and not the thermostat, and the system is filled properly, that leaves only the radiator. Once the thermostat cracks open, nothing will restrict flow except a rag in the hose or poorly flowing radiator. Cooling passeges are usually pretty big...



or your temp sensor is innacurate...[/quote]

Yes, that's true, except I've already taken the radiator to a shop to have it flow tested, and they said it's perfect, which makes sense, because it drains very nicely.



I wish it were the temp sensor, except the fat hose on the output side of the water pump (attached to the thermostat inlet) is downright cool to the touch, while the other hose is blazing hot. Also, I'm not getting any hot air inside the cabin when I turn on the heater and fan, so I'm sure the problem is real, unfortunately. I do agree that the trapped air idea seems a little far-fetched, since, as you say, the passages are huge. I'll start looking around for trapped rags in the hoses, I guess...



[quote name='rxter' post='54529' date='Jun 10 2008, 07:06 PM']This is like watching an episode of ER. Sorry that I am of no help here Cloud. It sounds like you have a garage full of the best Porsche mechanics around.[/quote]

Interesting you should use the ER analogy. Coincidentally, during the whole time I'm been struggling with this baffling cooling system problem, my 11-year old daughter has been down for the count with a mysterious headache/stomach ache that has completely escaped diagnosis. Up unitl very recently, none of the medications have helped, and none of the tests have turned up anything. The last medication the doctors have prescribed looks like it may finally be helping, so we're hopeful she's turned the corner. If it's true, I hope it's a good omen for my car, because this problem is really frustrating.

Partial Post: Please Login or Register to read the full post.

[rxter]

We'll keep a good thought for your daughter.

Partial Post: Please Login or Register to read the full post.

[xrad]

good luck to your daughter!







Do the impeller vanes face the right way (if it was a rebuild pump)?



Does the pump belt turn the pump correctly?



With the pump off, use a mirror and look in the passages, if possible. Then use a high pressure washer and jet in the inlet or outlet of the block. See if flow runs in one and out the other.



Check all coolant hoses for patency. Even the little ones to make sure all the air you can get out is really out



Just have to take this one step at a time until it is solved.

Partial Post: Please Login or Register to read the full post.

[RS Barn]

A few quick notes.

We see all sorts of cooling issues. I usually go for all possible fixes at one time.

I am now using a 160 degree thermostat on all cars. Stock and low temp units still are not low enough. Even with a low thermostat the coolant runs 180+

I have radiators cleaned. They pull off end and scrape debris from openings. There is usually an inch or two of sludge on bottom.

I use low temp thermo switch to kick on the fans earlier.

We are finding fan failures which show up initially as a blown fuse on one fan

Lots of failures or bad connections at coolant temp sensor (on block) to guage

I put a fan switch on DE cars to fire up fans at will

Pete

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='xrad' post='54646' date='Jun 12 2008, 05:16 PM']good luck to your daughter!







Do the impeller vanes face the right way (if it was a rebuild pump)?



Does the pump belt turn the pump correctly?



With the pump off, use a mirror and look in the passages, if possible. Then use a high pressure washer and jet in the inlet or outlet of the block. See if flow runs in one and out the other.



Check all coolant hoses for patency. Even the little ones to make sure all the air you can get out is really out



Just have to take this one step at a time until it is solved.[/quote]

Thanks for the kind words about my daughter. She's been essentially incapacitated for about a month and a half, and nobody can figure out why. She lately seems to very gradually be getting better, but her rate of improvement can best be described as "glacial," unfortunately. And this is a kid who won the first ice skating competition she entered just before she got sick.



I wish I had taken a closer look at my old water pump before sending it back for my core charge refund, because now I don't have anything to compare the reman pump to. To answer your questions, xrad, the pump's impellers actually point radially from the center to the edge of the impeller. To my surprise, they aren't curved in one direction or the other. Is this normal?



I'm pretty sure the belt is turning the pump correctly, because before I loosened the belt, I couldn't turn the pump by hand, so it's definitely applying plenty of pressure to the pump's roller. Overall, I'd have to say the pump looks very sturdy and well-engineered. In fact, Chuck from Paragon told me that compared to a new pump, the reman one to him looks like it has a more substantial casting, if that means anything. Also, I just got done placing it in a pot of boiling water to make sure the impeller is not coming loose of the shaft when it gets hot, and it isn't. I'm about as convinced as I can be at this point that it's not the pump, especially since the car started running warm long before I replaced the pump.



I don't have a high pressure washer, but I'll try flowing water through the block. I understand this is an important step, but I've been putting it off for two reasons: First, my driveway is on a slope, so I can't roll my car onto it, so flow testing will flood my garage, and second, since my block doesn't have a drain plug, I'm afraid that I won't be able to get the non-DI water completely out of the block.



I'll take another good look at the hoses. The two big hoses connecting the radiator to the enginer are fine, as is the small diameter hose connecting the bottom of the reservoir to the fitting on the front of the water pump. I'll check the rest as well.



Does anybody have a good diagram describing the path of water flow through the cooling system? There isn't one in the shop manual.



Thanks again for all the suggestions.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='RS Barn' post='54665' date='Jun 12 2008, 08:56 PM']A few quick notes.

We see all sorts of cooling issues. I usually go for all possible fixes at one time.

I am now using a 160 degree thermostat on all cars. Stock and low temp units still are not low enough. Even with a low thermostat the coolant runs 180+

I have radiators cleaned. They pull off end and scrape debris from openings. There is usually an inch or two of sludge on bottom.

I use low temp thermo switch to kick on the fans earlier.

We are finding fan failures which show up initially as a blown fuse on one fan

Lots of failures or bad connections at coolant temp sensor (on block) to guage

I put a fan switch on DE cars to fire up fans at will

Pete[/quote]

Pete,



Interesting comment about the thermostat. I checked both the one I bought from Paragon and the one from the Porsche dealer, and they both open at about 205 degrees, if I can believe the thermometer I had in the pot of water on the stovetop into which I dunked the thermostats. So obviously this is way above the temp you recommend. I don't see how this could explain the total lack of flow I'm seeing between my engine and radiator, because even a 205 degree thermostat would open eventually, right? Should I try running it with the thermostat removed?



I haven't had my radiator cleaned, but I took it to a radiator shop to have it flow tested, and they said it flowed perfectly. It also drains very well when I open the drain plug, so the rad appears to be healthy, as far as I can tell. I suppose it wouldn't hurt to have it cleaned, anyway, though.



The fans both kick in right as the needle gets just to the top of the 8 oclock line on the gauge, and they really blow up a storm, so things seen to be fine here as well.



Still scratching my head over this mystery... Would sure like to drive my car again someday...

Partial Post: Please Login or Register to read the full post.

[az968]

I've been experiencing a similar problem with my "93 coupe. But especially under power, climbing grades the temp gets between the top white mark and the bottom of the red failrly quickly. Backing off lowers the temp but substially lowers the fun factor too. I've been following this thread and some related ones and trying to diagnose the problem. Cloud 9..68, I haven't seen any comments for the past week or so. Did you solve your problem? If so, what did you finally do?



Thanks.

Partial Post: Please Login or Register to read the full post.

[SpeedRacer64]

Have you check the temp with an old fashion mercury temp guage....you maybe chasing an electronic value thats not right.

Partial Post: Please Login or Register to read the full post.

[prj24149]

I don't want to scare anyone, but was I having the same problem with the same overheating symptoms and I kept having to add coolant and bleed the system. Air was getting in and coolant out. I took it to my local Porsche shop and they found the head gasket had breached between one of the rear coolant flow channels and the outside at the rear of the engine. Coolant was leaking out and hitting the exhaust pipe. So I never saw any pooling of coolant. Luckily the gasket didn't breach into an oil channel or into the cylinder.

While having the head gasket replaced, we decided to do a valve job and do belts and rollers. $$$ <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[az968]

[In my car's situation the water pump hasn't been replaced so that not causing any of the problem. I did have a serious overheat last year when the heater control valve blew and all the coolant dumped out. Fortuantely this was 3 blocks from a service center and I had a new HCV (I know, why didn't I replace it sooner...). I've tried bleeding the system to no avail. The more I read on this the more concerned that it might be a head gasket.



Forgot to add that a IR heat guage showed reasonably similar temps between the upper and lower hoses to the engine block so I know coolant is passing thru the block. Those temps were reasonable and the car gauge was about the 9 oclock position.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

I haven't posted on this recently because I've been slowly been putting the front of my engine back on, after suspecting it may have been the water pump after all, but then finding that the impeller is definitely not loose on the shaft, even after placing it in a large pot of boiling water on the stove.



It's definitely not just the gauge, because the return hose isn't getting warm, nor is the heater blowing any warm air into the interior (though it did when I first installed this water pump in late March).



I also strongly doubt that it's a head gasket problem, because it isn't consuming any water whatsoever.



As far as the water pump impeller direction, it's kind of hard to tell. It looks like the impellers are pointing in a "neutral" direction, neither clockwise nor counter-clockwise. But I also don't really suspect the pump, because the car started running noticeably warmer late last summer, despite the summer of 2007 being extremely cool for central Texas - felt more like a Bay Area summer (where I grew up), than a Texas summer. I didn't replace the water pump till late March of this year, and the engine behaved EXACTLY the same, temperature-wise, after the pump/thermostat replacement as before.



I'm intrigued by Pete's comment that he likes to use 160 degree thermostats. Mine doesn't open until around 205-210 degrees, based on my stove-top test. Does anybody know the temperatures that the hash marks on the temp gauge correspond to? I've seen it posed here somewhere before, but I think it would be pretty time-consuming to find it. I believe it was Flash who posted it (so I guess I could do a search on posts by Flash, but that would probably set my computer on fire <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" /> ). Not sure if this would help explain my problem, but I'm curious.



I'm ready to install the radiator and refill my coolant (but am out of town for a few days, so it will have to wait till this weekend). I've deliberately left the thermostat out, because if it's still running hot, my next step will be to take it to a shop that can do a reverse flush, and from what I've read about this procedure on Google, it seems that it's typcially done with the thermostat out. I will bleed the system very methodically, to make sure I've gotten all the air out of it.



One bit of good news is that my daughter is doing much better. We've finally found a medicine that has taken care of her headache, so she's finally on the mend. Thanks for the thoughts and prayers. Now, if only my car can also be healed...

Partial Post: Please Login or Register to read the full post.

[az968]

Here's what my shop manual says the temp marks are:

Bottom of red mark - 115 C (239F)

Top white mark - 100 C (212 F)

Next down white mark - 80 C (176 F)

Top of bottom mark - 60 C (140 F)

Bottom of bottom mark - 40 C (104 F)



Very good to hear your daughter is responding. That has to be a load off your mind.

Partial Post: Please Login or Register to read the full post.

[flash]

the stock thermostat is 180 or something - if yours is not opening until over 200, i think you have found your problem - it happens - i've seen quite a few thermostats bad right out of the box



pete likes the 160 - we've talked about this - i don't necessarily disagree with him, but haven't had the chance to play with it myself



the goal is to have the needle move very little, regardless of operating temp - if a system is large enough, it will generally run 100 degrees over ambient temp or 15 degrees over the thermostat point, whichever is higher



it should also be at 190 - 195 for maximum performance



based on the degrees indicated by the hash marks, you should be a bit above the second line for maximum performance, and it should not move from there very much, no matter how hot or hard you run it



a 160 thermostat may be an effective patch for the inadequate radiator - in a perfect world, the stock 180 should be right, because at 15 degrees over that, it hits the magic number of 195 - this presumes a perfect cooling system though, and i'm not so sure we have that - pete has also found that most radiators are blocked - this is probably from people using tap water in there - a lower thermostat would open sooner, and increase flow during a longer period



there are a couple of potential complications of a low thermostat:



is in high heat climates you may reach too high of a temperature - it makes it very critical that the radiator flow as much as possible, there be a good mixture of coolant, and the hoses and cap be in perfect condition - a fresh 18lb or 19lb cap would definitely be in order



in colder climates, the engine never gets warm enough - this lowers the temp of the heater - more importantly, it lowers the temp around the combustion chamber - this means less performance, and potentially fuel wash in the cylinders - i had the extreme of this happen to me in an mgb - at a 160 thermostat we never got hot enough, fuel was not atomized enough, and washed the cylinder walls, tearing them up prematurely

Partial Post: Please Login or Register to read the full post.

[az968]

So maybe the best way to approach my car's overheating problem would be to:

1 - bleed coolant to make sure no air bubbles

2 - have radiator shop check radiator for blockage/clogging

3 - test thermostat for correct opening temp per Flash's recommendation

4 - test temp sensor to make sure it's registering correctly

5 - look at head gasket leak

???

Partial Post: Please Login or Register to read the full post.