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1990 944S2
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Water temp gauge funky?? Or??
Hi all
Recently replaced the hot side of my 944S2 radiator with an aluminum tank. (see p139 of "What I did to my car today" for a photo) Tank works fine but since the refit, the water temp gauge rides at around 1/4 hot (around 8:00 o'clock) and only rises above halfway in stop-and-go traffic and high heat (high 80s and up). It used to ride just under halfway (around 9 o'clock) most of the time. This could be the water temp gauge (but the fans work as normal) -- or not. I could just be running cooler (?) Anybody met this particular symptom before? Thanks! Chris
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84 944 gold sold 90 944S2 black current DD 89 735il white fixing 89 GL1500 white restoring, 01 955i S3 black current DD 01 955i Sprint brg customizing, 89 955i Daytona gold restoring |
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03-06-2015, 08:29 PM
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That Guy
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The water temp sender for the gauge is in the cylinder head, did you bleed the cooling system after making the repair? Might have some air stuck giving you false readings, though i would expect to see the gauge reading higher than normal as a result, not lower.
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Jon 1988 Granite Green 911 3.4L 2005 Arctic Silver 996 GT3 Past worth mentioning - 1987 924S, 1987 944, 1988 944T with 5.7L LS1 |
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03-07-2015, 05:24 AM
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1990 944S2
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Yes, I bled the cooling system several times. I'll do it a couple more times.
Onwards! Best Chris
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84 944 gold sold 90 944S2 black current DD 89 735il white fixing 89 GL1500 white restoring, 01 955i S3 black current DD 01 955i Sprint brg customizing, 89 955i Daytona gold restoring |
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03-07-2015, 07:31 AM
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Ornery Bastard
Join Date: Sep 2001
Location: South Sound
Posts: 2,879
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Air bubbles usually cause high temp readings, not low.
On an S2, at speed, coolant temps should run between 83 and 90 C (factory shop manual temps for the point where the thermostat begins to open and where it is completely open). This means that the gauge should run between just above the lower white line and halfway between the lower and upper white lines at speed depending on atmospheric conditions and ambient temps. It should run cooler at speed than it does when the car is stopped/barely moving unless ambient temps are really cold. The radiator fans come on in low-speed operation at coolant temps of 92 C (high speed is 102 C coolant temp, or A/C high-side line pressures over approx. 200 PSI). So when sitting still the coolant temps should run in the low-to-mid 90 C range unless it is exceptionally hot and humid (getting into the ambient range of 100 F). Just FYI, on a properly functioning gauge (no excessive resistance in the circuit), the lower white line is 80 C and the upper white line is 100 C. The red zone begins at 115 C. Note that high resistance (usually dirty grounds) will make the gauge read higher. So if you cleaned off some grounds while you were working on the radiator, you may have actually fixed a gauge that was reading slightly high before.
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--------- Silver 1998 Volvo S70 T5 <- Daily (Anja) Guards Red 1986 951 <- Seattle car (Gretchen) White 1976 914 2.0 F.I. <- Prodigal car, traded away then brought back again (Lorelei) |
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03-07-2015, 09:10 AM
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1990 944S2
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Many thanks, Duck and Aaron.
Nothing gaseous coming out of the bleeder section, so it's not that section, I don't think. Used a pressure tester, that usually pushes the air out the top, plus one can soon tell if there's air in the system that way. Don't think there is. So it could have been dirty contacts cleaned up... Bu I just drove over 100 miles yesterday (traffic, mid 90s, no overheating) and the problem persists.
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84 944 gold sold 90 944S2 black current DD 89 735il white fixing 89 GL1500 white restoring, 01 955i S3 black current DD 01 955i Sprint brg customizing, 89 955i Daytona gold restoring Last edited by ChrisRL; 03-08-2015 at 07:47 AM.. |
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03-08-2015, 06:56 AM
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Registered
Join Date: Jun 2014
Location: Lake County, FL
Posts: 820
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Changing the section over to aluminim is going to increase your heat transfer rate- not only did you increase the alluminum surface area but you bound each row together through it. Technically your radiator is larger now.
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03-08-2015, 11:58 AM
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Ornery Bastard
Join Date: Sep 2001
Location: South Sound
Posts: 2,879
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Quote:
If so it's possible that your thermostat has failed open. (Factory "begins to open" point is officially 83 C, but the shop manual says it's +/- 2 C, so the coldest an engine with a functioning factory thermostat should ever get once it's warmed up is 81 C.) Combining that with normal gauge error means I wouldn't worry unless temps were dropping below the "80 C" line after the engine was warm. As Brad mentioned the aluminum tank will be shedding heat better than the original tanks, and it's further likely that the radiator got cleaned and flushed when the work was done, which likely further increased its efficiency. So a slightly stuck open thermostat combined with a less-efficient-than-new radiator might have been enough to keep you from noticing either, but now that your radiator is clean and has the better heat dissipation of the aluminum end tank as well, you might be now able to notice a slightly stuck open thermostat that you couldn't before. Can you clarify where the needle is pointing based on the image attached to this post? 
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--------- Silver 1998 Volvo S70 T5 <- Daily (Anja) Guards Red 1986 951 <- Seattle car (Gretchen) White 1976 914 2.0 F.I. <- Prodigal car, traded away then brought back again (Lorelei) |
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03-08-2015, 01:43 PM
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The Kraut Burner
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