tylenol

Have had the car for a few months replaced Lh and maf running great but the temp gauge moves around between 2nd line and third line while driving. Never goes over third line??? Is this normal?? Thanks

Rich9928p

Yes, quite normal - my S4 and GTS both run a little under or over the 2/3rds mark - even during the hot AZ summers. Under spirited driving or very steep grades at high throttle (like a drive in Death Valley), the needle may move up close to the red zone and you're still OK. If it doesn't drop back down when you throttle down or if it continues up into the red then you do need to stop and let it cool down and determine if you have a problem (low coolant, blockage in airflow, failed radiator fan (or two).

tylenol

thanks I was almost scarred to drive it...a little gunshy after the first couple of problems!!

blown 87

It is also common for the temp gauges to be just wrong.
Mine will show at the top white line and the temp going into the radiator is below 200.

Mrmerlin

since you just got the car a few things should be inspected one is to replace the O ring and rear thermostat seal and the heater control valve and short hose, also inspect the 3 way fitting for the charcoal canister in the right fenderwell this will let you have piece of mind that the little things dont turn into big things

JCP1990S4

Mine runs right up to the last white line even on cool days. I even invested in a new high flow radiator. I've done everything, I just think they run hot no matter what.

WICruiser

Temp guages are not known to be accurate. If the temperature is stable then check with an infrared heat gun or some other means to check coolant temperature.

Mine was running very high in the white, not red, and one of the times I had the cluster out I checked the guage - it was biased high relative to the travel range. Once I centered the needle to the travel range it now runs slightly above the 2nd white line. Of course that was not unitl after I had replaced the thermostat and rear thermostat seal, etc., etc.

928 at last

Use the IR gun! Best way to check without getting too involved. Mine runs just shy of the third line once it's warmed up and that can be in 40 degrees or 102 degrees.

Footnote: Yes it gets that hot here...just not often. Today was really hot, and more to come.

dr bob

I notice that on the temp gauge, they don't give a number for the mark between 170º and the mark that looks like it's the 210º mark. I just ASSume that it's 190º. Is it really 210º and the red line is closer to design boiling point of 230º?

Mine runs in the middle of that 170-?? mark range. I don't give it any concern so long as it stays there. On really hot (100º+ ambient) days with high load, it has crept a needle-width or two above that higher mark, and at that time I give the gauge more attention. Point is that you'll figure out what the car does in 'normal' situations, and then start paying a bit more attention when it does something abnormal. If there's a logical reason for it running a bit warmer at that time, you'll be more alert to what it's doing. If there's no logical explanation, find out what's causing the abnormality.

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Regular cooling system service is a must on these cars. Even with 'extended life' coolants, a maximum of two years between changes is a good idea. Use a correct coolant. I've seen plentyu ofcars with good old green Prestone in them, and they seemed OK. Some folks swear by the blue Autobahn coolant sold by VW/Audi/Porsche or their own brands. I've been using the G-05 with good performance. Opinions on best coolant are like asking which oil is best. The best one is the the one that's changed regularly, including a full block flush every time.

The thermostat system is somewhat unique, and certainly different from what you typically see in US cars. It bypasses the radiator when cold, then closes the bypass port and opens the radiator flow when warm. That bypass port has a seal directly behind the thermostat that should be changed with the thermostat but seldom is. I change the thermostat and rear seal when I do a timing belt change, and generally change all the coolant hoses every other timing belt change. I've seen cars with original hoses throughout, so maybe I'm over-cautious. But I hate getting stranded by Stupid Stuff, and don't want to risk the motor for a tired coolant hose.

The coolant reservoir cap gets renewed at every timing belt change. Get the OEM Behr cap when you order your TB parts. If the cap won't hold pressure, the capacity of the system will be severely reduced. I can give the whole physics lesson, but it takes longer to do that than it does to just replace the cap.

The original reservoirs themselves are getting old and tired. They do like to crack, and will bleed coolant. Since this is often an under-pressure leak only, you may not notice it until you get a low-coolant warning. Danger is similar to a failing cap, plus the low coolant problem. If you are doing a TB job or even just the annual flush-and-replace with coolant, consider replacing that tired old original reservoir with a new one. They are around $100 IIRC, and take seven bad words and less than an hour to replace.

I use Redline Water Wetter in the coolant. It's worth 15-20º of extra cooling in my old Explorer on hot days. If it hepls the 928 the same it's a great $8 investment. One is enough I think, even with the large coolant system capacity.

Coolant is diluted in distilled water in my car. Minerals that aren't in the water can't plate out on the walls of the system. I do a lot of work teaching people how to run steam boilers in power plants, where water chemistry is an obsession. The cooling system is everthing a staem boiler would love to be, minus the high heat and pressure. Distilled water is cheap at the grocery store.