[Cloud9...68]

[quote name='az968' post='55350' date='Jun 24 2008, 11:53 PM']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.[/quote]

Thanks for this info. I looked in the manual, but couldn't find it. Where did you find this? There's not a whole lot in my copy of the manual in the cooling system section. I guess in Arizona, it beehoves one to know these temperatures <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> I know, I lived in Phoenix for 11 years.



Both of the thermostats I installed in my car recently (one from Paragon, one from Porsche) opened at 205-210 degrees. The last time I drove my car, the gauge got to the upper white line, which is at 212 degrees. So, there thermostat should have opened by then, allowing water to flow to the radiator. But when I got the car home, the bottom radiator hose was cool. Hmmm... doesn't really sound like the thermostat is the problem.



And thanks for the encouraging words about my daughter; yes, it's been a huge relief to see her free of pain.

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[Cloud9...68]

[quote name='flash' post='55354' date='Jun 25 2008, 07:51 AM']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



>>But two of them? I suppose stranger things have happened, but it seems odd that a thermostat from Paragon, and one from Porsche, would both be bad at exactly the same point. I wonder if the problem was actually with the cooking thermometer I was using to measure the temperatue. I'll have to check that when I get home.



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



>>Wow, so it should be at the 10:00 oclock line? It NEVER reached this point in prior years, even though the summers of 2004, 2005, and 2006 were MUCH hotter than the summer of 2007 in Austin. I never saw it get above the 8 oclock like before last summer. I'm really starting to get confused.



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



>> I think I'll go ahead and have the radiator cleaned. I wasn't planning on doing that, since the last shop I took the radiator to said it was flowing fine, but It can't hurt to have it cleaned out, as long as it's still out of the car.



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[/quote]

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[SILVY968]

While we are on the topic of heat and the fact that summer is here...try water wetter. Great product that has dropped my temp down nicely. Couldn't hurt with an aluminum engine cooled by a football sized hole in its nose that is helped by thermostatically controlled relay switched fans in a German sports car with expensive parts.

Whew!

Brian

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[az968]

[quote name='Cloud9...68' post='55412' date='Jun 25 2008, 07:31 PM']Thanks for this info. I looked in the manual, but couldn't find it. Where did you find this? There's not a whole lot in my copy of the manual in the cooling system section. I guess in Arizona, it beehoves one to know these temperatures <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> I know, I lived in Phoenix for 11 years.

> I found it in the Porsche shop manual, actually in the 944 part. They show two guage styles, the later one matches the 968 guage style. There wasn't an update in the 968 section so I am presuming nothing changed between the models in this area.



> Well, I lived in Austin for 7 years and the humidity there makes it just as hot. <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" /> Now I live in the mountains where 95 is a very hot day.





Both of the thermostats I installed in my car recently (one from Paragon, one from Porsche) opened at 205-210 degrees. The last time I drove my car, the gauge got to the upper white line, which is at 212 degrees. So, there thermostat should have opened by then, allowing water to flow to the radiator. But when I got the car home, the bottom radiator hose was cool. Hmmm... doesn't really sound like the thermostat is the problem.



And thanks for the encouraging words about my daughter; yes, it's been a huge relief to see her free of pain.[/quote]

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[Cloud9...68]

az968- You lived in both Austin and Phoenix? Do you by chance work for Freescale Semiconductor? I've been with Motorola/Freescale since 1981.

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[Cloud9...68]

I had a thought as I was posting a reply on another thread: The PO told me he installed a low temp fan switch (both my fans come on at when the temp gauge hits the 8 oclock line, which corresponds to about 180 deg F. If he had (correctly) installed a low temp thermostat when he installed the low temp fan switch, everything should have been working in harmony, which it was, because my temp gauge, until late last year, almost never budged above the 8 oclock line, even on the hottest central Texas day, even at the track.



I know I now have a standard 190 degree thermostat (which I installed when I did my belts, seals, rollers, and water pump this past March). Is it possible that now that I have a low temp fan switch, but a "high" temp thermostat, the fans are keeping the water in the radiator too cool to get the thermostat to open? Given the direction of flow, this seems to make sense. Thoughts?

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[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,



Where can I find a 160 degree thermostat? I looked on both Paragon's and Pelican's web sites, and didn't see any non-standard temp thermostats listed on either site.



Do you think it's possible that the fact that I'm running a low temp fan switch with a standard (190 deg F) thermostat could be the cause of why I'm not getting coolant flow between my radiator and engine? Thanks.

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[flash]

i am running a low temp fan switch and a standard thermostat - no issues - i don't think that is your problem



the fact that both of your thermostats open so late makes me wonder what's up there though - when i boil mine, they crack open just BEFORE the indicated temp, not well after - could just be your thermometer though



i'm still going with defective thermostat or major blockage



one quick note - the system does not work well if it won't hold pressure - have you tried pressurizing the system to see if it holds at least 15lbs? please be careful not to force too much pressure in there though

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[RS Barn]

The 160 degree unit is a NAPA #38 or Stant 13376 availble at Pep boys.

Coolant in the car will run 180-190 when using the 160 thermostat. The Bosch Hammer lets you measure coolant temp as you drive and on a 70 degree day I saw 180-190 while driving and stopped. This was with a low temp fan switch. At a traffic light the low speed fan would come on.

The only downside I see to 160 stat is in cold weather warmup will take much longer.

The symptom of waterpump failure is upper hose stays cool while lower is hot. The thermos switch won't tell the fans to work even if temp is high

Pete

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[flash]

180-190 isn't horrible, but still a little bit low - if it pops up to 195 while driving, then it's probably ok - if it goes down, then that's bad for performance, cylinder life, and emissions - i always thought cooler was better, but it appears that too cool is bad - i found out the hard and rather expensive way



my car runs a bit cooler than i'd like when it's not hot enough outside - once it gets to 80 or so, then it's fine - i may try the lower thermostat and the higher fan switch

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[Cloud9...68]

Thanks for the inputs, guys. This problem is really starting to get on my nerves, so I appreciate the continued support. I'm going to have to re-learn how to drive a stickshift by the time this car gets running again...



Here's the latest:



I had the radiator rodded out this Saturday. The guy took the end caps off, and physically got in there with a brush. He said it was very clean. So it's not the radiator.



As far as I can tell, it looks like the water pump drives the water into the block, and then into the radiator through the upper hose. Then the wafer flows through the radiator, and through the lower hose, into the thermostat. Based on the fact that the upper hose is getting very hot, it appears that the water pump is at least doing its job of pumping water through the engine and into the radiator. So I don't think it's the water pump.



I have pressure checked the system to 15 lbs, and it's tight, so this doesn't appear to be it.



My next step is to boil both of my new thermostats, using a different thermometer. I spoke to Pete today, and he told me he has seen thermostats not open till over 200 deg, so I'm holding out hope that I'm suffering from a very large mismatch between the fan switch temperature, and the thermostat opening temp. Maybe if I had driven the car longer the last time I drove it, the temperature of the water coming from the radiator would have eventually gotten warm enough to open the thermostat, enabling flow through the system, but I got nervous seeing it hit the 10 oclock line, which it had never come close to before, so I limped home.



I'm clinging to this hope because of an interesting observation I made on this last drive: When the car was stopped at a light, the temperature actually dropped a bit, contrary to expectations. I'm wondering if this means the water flowing from the engine through the radiator was finally getting hot enough, despite the fans' best efforts to cool it down, to begin to crack open the thermostat. When I pulled away from the light, the gauge indication actually started climbing again. Weird, but that's what it did. Doesn't this argue against a blockage? The passages through the block and head are quite large, right, so a blockage would seem to be somewhat unlikely, especially since the radiator was so clean, indicating the previous owner(s) did a good job of keeping up with the cooling system maintenance.



Flash, can you tell what temperature your fans come on? Both of mine (I'm pretty sure; when I finally get it running, I'll check to see if both speeds of mine work, but I don't think the low speed ever happens) come on right at the 8 oclock line, which is 176 degrees.



I'll continue to keep everybody posted. As usual, I hope my adventure with this problem will help somebody else down the road.

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[flash]

my low speed comes on at about 185 - my high speed has never come on (other than with the AC on), so i don't know for sure, but the switch is set for about 200

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[RS Barn]

Another regular find is rad caps not holding pressure.

Stock is just about 19lbs. Way higher than we're acustomed to. We chec them regularly and se 10-12lbs or so. I install Stant racing caps that hold to 21psi.

Pete

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[Cloud9...68]

Thanks, Flash. So the delta between when your fans come on and when your thermostat opens is quite small. Seems that yours are behaving the opposite of mine, in that I'm pretty sure my low speed never comes on, although it's been so long that the car has run, I'm not really positive about anything anymore. I'll definitely check it when I finally get it running. Yours sound like they're working correctly. It's possible that my PO installed a 944 switch; I thought I read that the 944 switch is single-speed.



OK, here's some data on my thermostats, taken with a different thermometer:



Paragon-supplied: Starts to open at 190 deg, fully open at 200 deg, closes back up at 175 deg

Porsche dealer-supplied: Starts to open at 198 deg, never fully opens when water boils, closes back up at 175 deg



So, clearly, the two thermostats are different. The Paragon-supplied one appears to be behaving correctly. The Porsche-supplied one is the one I had in the car when the gauge hit the 10 oclock mark. So, maybe it would eventually have opened, but I'm afraid the coolant in the engine would have had to have gotten VERY by the time the coolant in the radiator overcame the cyclone the fans were blowing through it, and the water in the lower hose got hot enough to open the thermostat.



So Flash, you're right, the cause of my engine getting as hot as it did the last time I drove it was almost certainly a bad thermostat. This I believe leaves me three choices:



1) Put the Paragon thermostat back in. Now that I see how the two thermostats are behaving side by side, I'm more in favor of this than before, but I'm still concerned over the fact that the lower hose didn't get warm the last time I drove the car with the Paragon thermostat. Maybe on a warmer day, the thermostat would have opened, so maybe I need to give it another chance now that it's much hotter.



2) Buy a 160 deg thermostat and install it. The Stant unit isn't available locally, so I'll have to see if Napa has one if I decide to go this route.



3) Leave the thermostat out altogether to see if I'm even on the right track. The only downside to this is that, while taking the thermostat in and out is easy, it makes a mess.



What would you guys do if you were me? Thanks.

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[xrad]

put in a 180 T-stat with a new rubber seal. I only use the T-stat rubber ring held in by the stainless washer and clip, not the inner seal as in some diagrams.



don;t leave T-stat out. engine runs best at certain temp as designed by porsche.

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[az968]

[quote name='Cloud9...68' post='55574' date='Jun 29 2008, 09:14 AM']az968- You lived in both Austin and Phoenix? Do you by chance work for Freescale Semiconductor? I've been with Motorola/Freescale since 1981.[/quote]

I retired from Motorola 3 years ago after 27 years. I was based in the Ed Bluestein facilitey from 76-83, then to Schaumburg for 8 yrs before back to Phx. I was in Corp IT.

What did you do in 81-83?

Small world.

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[wingers]

The start of a head gasket or warped head maybe!

Maybe time to do a exhaust gas analyser [or head leakage chemical test] check in the cooling header tank.



May not be bad enough to show up on a leak down test yet!

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[Cloud9...68]

[quote name='xrad' post='55641' date='Jun 30 2008, 09:15 PM']put in a 180 T-stat with a new rubber seal. I only use the T-stat rubber ring held in by the stainless washer and clip, not the inner seal as in some diagrams.



don;t leave T-stat out. engine runs best at certain temp as designed by porsche.[/quote]

I've slept on this (literally; spent a few sleepless minutes kicking it around), and have come to the following conclusions:



I agree with you, a 180 deg thermostat would be a good choice. The problem I have is that the spec on the standard thermostat is 180 degrees, and I've bought two recently, the closer of the two being 10 degrees above spec! The other one was ridiculously far off, and in talking to Pete, he has seen similar results. So I'm wonderinig how many more thermostats I'd have to buy and test before I found one that meets spec.



I suspect that the one I had in the car until this past March was either on target at 180 deg, or maybe was even a 160 deg unit. So, I'm inclined to follow Pete's recommendation and buy a 160 degree unit, since I'm sure this would open even with the fans blowing full blast. Again, I think my system is abnormally sensitive to thermostat opening temperature because the low temp fan switch the PO installed is cooling the water in the radiator before it has a chance to open the thrmostat. Here in warm Central Texas, I think I can get away with a 160 degree thermostat, especially in the summer. If the engine has trouble getting up to temp in a timely fashion this winter, I'll pop the Paragon 190 deg thermostat back in.

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[Cloud9...68]

[quote name='winger' post='55648' date='Jul 1 2008, 01:45 AM']The start of a head gasket or warped head maybe!

Maybe time to do a exhaust gas analyser [or head leakage chemical test] check in the cooling header tank.



May not be bad enough to show up on a leak down test yet![/quote]

I don't think a warped head is my problem (at least not the one on my engine <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> ). I'm not losing a drop of coolant anywhere, a recent oil analysis showed zero antifreeze in the oil, and it just had its state inspection, which included an exhaust gas analysis, and it passed with flying colors.



My problem is 100% driven by a lack of coolant flow, and the temperature seen on the gauge is dramatically impacted by the opening temperature of the thermostat. I've recently run with two thermostats, whose opening temperatures are about 10 degrees off from each other (both are well above the 180 deg spec), and am seeing a huge difference in indicated temp (barely 9 oclock with one thermostat, well into 10 oclock territory with the other).



[quote name='RS Barn' post='55638' date='Jun 30 2008, 08:18 PM']Another regular find is rad caps not holding pressure.

Stock is just about 19lbs. Way higher than we're acustomed to. We chec them regularly and se 10-12lbs or so. I install Stant racing caps that hold to 21psi.

Pete[/quote]

Makes sense; I've tried to get my cap tested, but haven't found anybody locally who can do it (though I haven't exactly checked a ton of places). Once I get coolant flowing through the lower hose, I'll go ahead and replace the cap. Thanks.

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[wingers]

[quote name='Cloud9...68' post='55664' date='Jul 1 2008, 07:44 AM']I don't think a warped head is my problem (at least not the one on my engine <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> ). I'm not losing a drop of coolant anywhere, a recent oil analysis showed zero antifreeze in the oil, and it just had its state inspection, which included an exhaust gas analysis, and it passed with flying colors.



My problem is 100% driven by a lack of coolant flow, and the temperature seen on the gauge is dramatically impacted by the opening temperature of the thermostat. I've recently run with two thermostats, whose opening temperatures are about 10 degrees off from each other (both are well above the 180 deg spec), and am seeing a huge difference in indicated temp (barely 9 oclock with one thermostat, well into 10 oclock territory with the other).





Makes sense; I've tried to get my cap tested, but haven't found anybody locally who can do it (though I haven't exactly checked a ton of places). Once I get coolant flowing through the lower hose, I'll go ahead and replace the cap. Thanks.[/quote]



The check in the header tank with the emission tester was for any carbon monoxide present indicating a leaking head gasket etc.

When it's just beginning, a head gasket leak can be so small that symptoms are not yet noticeable. In such a case professional testing, checking for carbon monoxide gas in the cooling system, will point out the problem.

Fitting a higher pressure cap will drop the temp but may cause other cooling related probs. ie water pump seal leak!

The head leakage chemical test is used when the gasket is just starting to fail, the test is carried out with a fluid that the air in the header is passed through and changes from blue to a clear when a failure is detected.

Small amount of air build up round temp sensors may well put the fans, temp gauge in to a mind of there own.

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