[Cloud9...68]

[quote name='winger' post='55675' date='Jul 1 2008, 04:09 PM']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.[/quote]

Your advice to test for a head gasket leak sounds reasonable, and is probably something I should look into when I get my car up and running. However, again, my overheating problem is caused by the fact that I'm simply not getting any circulation of coolant between my engine and the radiator. Also, the fans' behavior hasn't changed, and the temp gauge is behaving consistently with the fact that I'm not getting any coolant flow through the lower rad hose, and that the heater doesn't blow hot air.



However, Pete has advised for a long time that after 100,000 miles or so, the head usually needs a "freshening," which of course would include a new gasket. Can any shop do the CO test you're describing, or is it a fairly specialized test? Thanks.

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[wingers]

[quote name='Cloud9...68' post='55677' date='Jul 1 2008, 04:28 PM']Your advice to test for a head gasket leak sounds reasonable, and is probably something I should look into when I get my car up and running. However, again, my overheating problem is caused by the fact that I'm simply not getting any circulation of coolant between my engine and the radiator. Also, the fans' behavior hasn't changed, and the temp gauge is behaving consistently with the fact that I'm not getting any coolant flow through the lower rad hose, and that the heater doesn't blow hot air.



However, Pete has advised for a long time that after 100,000 miles or so, the head usually needs a "freshening," which of course would include a new gasket. Can any shop do the CO test you're describing, or is it a fairly specialized test? Thanks.[/quote]



Any workshop can do the test with a emission tester providing they are happy about it.

Care must be taken not to allow an water into the sample prob.

Better to lower the water level in the header tank before testing with the engine running as blow back can sometimes occur.but the gasket or head fault is in full failure mode by then.



The chemical test is also carried out with a low water level ,sniffing the air in the coolant, changing colour if carbon monoxide is present.



Couple of other things, has the heater valve been replaced through leakage?

What happens to temp when the heater is fully hot on with the blower at max?



Flash, log on seems ok now thanks.

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[Cloud9...68]

[quote name='winger' post='55727' date='Jul 2 2008, 02:24 PM']Any workshop can do the test with a emission tester providing they are happy about it.

Care must be taken not to allow an water into the sample prob.

Better to lower the water level in the header tank before testing with the engine running as blow back can sometimes occur.but the gasket or head fault is in full failure mode by then.



The chemical test is also carried out with a low water level ,sniffing the air in the coolant, changing colour if carbon monoxide is present.



Couple of other things, has the heater valve been replaced through leakage?

What happens to temp when the heater is fully hot on with the blower at max?



Flash, log on seems ok now thanks.[/quote]

Thanks. I replaced the heater valve a couple years ago with an Audi all-metal one as a preventative, and it has never leaked. When the heater is on fully hot with the blower at max, the temp indication on the gauge doesn't move at all, and only lukewarm air blows from the vents. Again, this is indicative of a lack of coolant flow. I bought a 160 deg thremostat today, and will install it, and bleed the system, asap. Hope to be back on the road soon!

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[Cloud9...68]

[quote name='az968' post='55647' date='Jun 30 2008, 11:31 PM']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.[/quote]

Sorry for slow response. I've spent my whole career at Motorola's semiconductor division (mostly in R & D), which spun off in 2004 as Freescale Semiconductor. I graduated in January of 82, but did a summer internship in Phoenix in 81. I started work in Phoenix after graduating, and was in Phoenix from 82-92, when I moved to Austin, where I've been ever since. Pretty amazing that I've been doing pretty much the same thing for the same company for 27 years. The work's always challenging and interesting, though, so I can't complain.

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[Lim Yong]

Hi all,

Just as Pete mentioned earlier in this thread... fan Fuse is blowing and I discover one of the fans are not turning. Does anyone know if I need to replace the whole fan shroud (both fans)? or just one fan motor?



I think reading about 968 problems on this forum and I think it is contagious... I am have multiple problems lately, waterpump, AC condenser (and snap bolts), and now fan. Oh, forgot, sunroof now not going up but the motor is working.



Thanks everyone for all the advice, past and future.....

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[Mark]

[quote name='Cloud9...68' post='55662' date='Jul 1 2008, 10:34 AM']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 wondering how many more thermostats I'd have to buy and test before I found one that meets spec.[/quote]



I know when Pete was messing with mine it took 4 or 5 before he found one that opened close to 180.

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[Cloud9...68]

Woo-hoo!!!!! Success!!! Finally, we have flow. So, the 160 deg spec'd (175 deg actual measured opening temperature) thermostat did the trick. I drove the car on many errands in the middle of the day today, with the ambient around 95 deg, and the gauge remained well behaved. So, the morals of my long story are:



- A good thermostat is hard to find. All three that I tested opened well above their stated opening temperature.



- If you install a low temp fan switch, pay very close attention to the thermostat opening temperature. I suspect that the one that was in mine before I replaced it this past March was either a low temp unit, or it was spot-on at the specified stock opening temp of 180 deg. I haven't seen a flow diagram for the 968's cooling system, nor do I have X-ray vision, but it looks to me that the water pump pushes the water first through the block (and maybe the head), then back through the upper hose, one lap through the radiator, and then back to the engine. The thermostat sits at the mouth of the return hose. I think my problem was rooted in the fact that my fans come on at 175 deg, which was cooling down the water too much during its one lap through the radiator to allow the 198 deg thermostat (the measured opening temp of the last one I had in there). When I replaced this t-stat with the present lower temp unit, it opens fine, despite the fact that the water is getting cooled due to the fact that the fans come on at about 175 deg. If I had had the standard fan switch, things may have worked fine with the higher temp t-stats, but with the low temp fan switch, I need a correspondingly lower temp t-stat. I'm happy that the one I got opens at 175 deg, rather than the stated 160 deg, as I think the set-up I now have will work fine in both the summer and winter.



Many thanks for all who helped me out with the puzzling problem. I hope my experience helps somebody else at some point.

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[Ryan]

Well thank God it's over. I am sure you were about to through a match in the gas tank after all the removing and puttin back that was done. Glad it all worked out. Drive man drive......

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[Cloud9...68]

[quote name='Ryan' post='56235' date='Jul 12 2008, 06:16 PM']I am sure you were about to through a match in the gas tank after all the removing and puttin back that was done.[/quote]

Lol. You're not far off. If it had turned out after all this, that it was the water pump after all, I think I would have layed down on my driveway and asked a neighbor to run me over a few times. But it sure is running well now, and at what appears to be a perfect temperature range.



I realized when I finally fired it up last night that the gas that's in the tank is probably close to a buck a gallon cheaper than the stuff for sale now. Hmmm... should I drain it out, and sell it for a profit <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" /> ? Sorry, getting a little punchy, after driving the minivan everywhere for a couple of months...

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[flash]

pardon the obvious pun, but COOL!



it sounded to me like a thermostat problem, and i'm glad that's all it was

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[Cloud9...68]

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

After driving my car around on some very hot afternoons over the past couple of weeks, it seems to be adhering perfectly to the guidelines Flash posted. For example, on a 100 deg day, the needle is just a tad beyond the midpoint between the 8:00 oclock and 9:00 oclock lines, or right smack at 200 degrees. When it's cooler out (like at nighttime after a hot day), it hovers right at the 8:00 oclock line. So everything seems to be working perfectly.



I'm just curious; is this how most peoples' temp gauges behave? For you folks in Phoenix, on a 110 deg or higher day, does you gauge hit the 10:00 oclock line? I'm asking because, and my memory could well be faulty here, before I did all this work to my engine, and installed the current 160 deg thermostat, I don't recall seeing the needle ever get above the 8:00 oclock line. So, it seems to be running a bit warmer than before, but, again, it also seems to be operating exactly as it's supposed to. Thanks.

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[flash]

glad it is working out - now if i could just get mine to warm up a bit, i'd be fine - driving it the other day, in 90 degree heat, the oil temp was 195 and the water was 176 - made me a bit nutty - i'm stuck between "cool - it's running nice and cold" and "bummer - i might be fuel washing my cylinders"



it does warm up though when i really get on it - pops right into the sweet spot - so, maybe it's not all bad

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[Cloud9...68]

Thanks, and thanks for your suggestion to focus on the thermostat - you were right.



At 90 degrees ambient, mine also runs right at about 176 deg water temp (I don't have an oil temp gauge - it's long been on my to do list). So, it seems that this is pretty normal for these cars.



I'm also very pleased with how it's behaving in stop-and-go traffic. The fans do a great job of keeping the temp under control in the absence of movement. When it began running hot late last summer, it would get quite a bit warmer at idle than it does now.

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[flash]

yeah - i know it seems nuts sometimes, but you know occam's razor



sounds like it is definitely operating like it should now - unfortunately many of these cars do not, and consequently what people experience is what they think is "normal", not knowing that it should really be doing something different



a lot of the problems we see in cooling systems are from people using tap water - this is a big no-no - often people will follow the instructions about phosphate free coolant, only to pollute it with deposit ridden water - the deposits in the water cause components to operate in a manner they should not - get it on the thermostat and it doesn't open at the right temp - get it on the impeller and it doesn't pump right - get it stuck in the radiator and all hell breaks loose



but, glad you got it all sorted out

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