New 924S owner with speedometer, cooling system questions

[austinporsche]

Hi all.

Though I have been a member of the Pelican forum for 7+ years now (and buying from them since maybe '94?), it has always been for my '73 911T-- the long hood forum.

In the last year, however, I have acquired several front engine water cooled Zuffenhauser products: an '88 924S, '86 928S, four --yes four -- 944s (2 complete cars, 2 rolling donors, none running yet).

I've had the 924S for about 6-7 months now and am finally getting around to getting it sorted (so my son can drive it this summer).

It has two (2) issues requiring immediate attention:

1. The coolant temperature gauge runs very hot
2. The speedometer needle "bounces" a bunch above about 20mph (and the odometer doesn't work, though the trip meter does).

Regarding the cooling temp gauge reading hot/high, it appears to be functioning because when it was cold here in Austin, it would read at about 60-70% of max, when warm/hot here, it reads about 85-90% of max.

The seller (via BAT -- bring a trailer) told me that it was just a coolant temp sensor ground issue, and I am taking him at his word (after all he gave me a very, very, very good -- dare I say screaming -- deal on a 928S with a bad 2nd gear synchro and non-working AC but otherwise sound car in a two-fer deal).

I am guessing that when it's cold, say below 30 degrees, the normal needle reading would be at 40% of max, not 60%, and 50-60% when the ambient temp is hot, so maybe it really is a calibration/ground issue?

How would one suggest I go about troubleshooting this to determine whether it really is a ground versus something else: bad sensor, thermostat, clogged radiator, etc.? I just got done sorting out all the electrical on an X1/9 I bought (it had priority as I was driving it targa-off during the cooler than usual winter/spring here in central Texas), so am pretty handy with a multimeter and wiring diagram right now (and the Fiat had lots of ground/resistance problems).

The issue with the speedo is more of an irritant. I am guessing that it is the speedo gauge itself and not the speed sensor because there is an issue not only with the speedometer needle not reading accurately/bouncing around -- sometimes it does it continuously, other times it settles down after driving it a while -- but also with the odometer, so my issue is with the whole speedo gauge in the instrument cluster.

Does everyone agree with this or could it be the speed sensor? (presumably, the speed sensor also drive the odometer and trip meter mechanisms as well?)

Can these be repaired or do I need a new cluster? Haven't taken it out yet, but Haynes says the cluster is a one-piece integrated unit.

If so, is the 944 cluster a plug-and-play as I have four of those and long-term will only need two? Or is there someone that fixes these clusters relatively cheaply?

Otherwise, I love the 924 -- always wanted one since I was a kid -- and look forward to driving it a bunch once I have these little irritants sorted out, especially since it has great R134 AC while the 911T doesn't and the 928 does but it doesn't work yet (too many projects).

[Mr. Squid]

Sounds like quite the collection of cars. Hopefully you have loads of spare time for wrenching! jk

Speedometer - This is a mechanical speedometer and is cable driven by a cable that goes to the Left Front wheel. Could be the cable or the speedometer. Good news, if you have some pre 85.5 944 you should have the parts to fix it. If you remove the left front wheel, you will see the end of the cable poking out of the bearing cap with a C-Clip holding it in place. The speedometer is not hard to replace, and maybe you want to start there. The ones in the 944 have yellow lettering vs. the 924S white lettering. You can get creative and remove the lens and swap the face of the gauge if necessary.

Cooling System - My guess is a cooling system issue. Do the fans come on as it gets up to temp (both fans?). Has the timing belt and waterpump been done recently? If not, you should be changing those soon to prevent having to replace your cylinder head from a broken timing belt. At the same time you can flush the cooling system and put in a lower temp thermostat along with a lower temp fan switch to kick the fans on earlier.

My similar issues - My 924S had a jumping speedometer, I ordered a new cable and replaced it only to find out it was the speedometer all along. My 924S also ran hot for a while. It had a "New" aftermarket radiator from a parts store, the radiator core was actually thinner than OE. I swapped in a good used radiator and the problem went away.

[austinporsche]

Thanks, Squid.

The Porsche 944 Haynes indicated that the speed sensor was electrical and at the transmission -- guessing that's not the case?

What should I look for at the hub end of the cable to see if it has failed? And how hard is it to route a new cable?

If not the cable, how did you fix your speedo gauge issue: new speedo or did you repair it? I know they have a plastic gear inside the speedo -- 17 tooth -- that fails eventually.

Regarding the cooling system, no chance it could be a ground/electrical issue then?

I will listen to/check out the fans.

There are a range of thermostats out there: 160, 176, 180, 190. Being in Texas, should I go with the 160?

Yeah I am stupid when it comes to cars. Collection (with my brother as keeper) includes:

'32 Ford Coupe (currently putting a '96 Saab turbo engine in it just to be different)
'40 Ford (2 of them)
2 '60s vintage Sand Rails (what they call dune buggies here in Texas, both with VW air cooled engines)
1973 'Vette
1973.5 911T (coupe, body-off resto, original gold color -- what my wife derisively calls "baby diarrhea yellow")
1979 Firebird
1981 X1/9
1982 RX7 (flawless, maybe best example of a GSL out there)
1983 944 (flood car from Houston with non-repairable title)
1986 944 (three of them)
1986 928S
1988 924S
1992 Kawasaki Ninja
1996 Saab (runs and drives but is eventual donor for the '32 Ford)
2000 1500 pickup
2000 Honda Insight (manual)
2003 Honda Insight (CVT)
2004 Land Rover Discovery 2
2004 T&C Minivan
2004 Saab 9-3 Arc (super fast, 150+)
2004 RX8
2007 T&C Minivan
2007 Saab 9-3 Linear

Maybe missing one or two others that I can't remember (are not important).

Still looking for a 1979-1981 Scirocco, TR8 (same block as the Land Rover), Spitfire (overdrive), 320i, 633/635CSi. Oh, and a 914 (had a '75 when I lived the Bay Watch life in Hermosa Beach in the '80s, but I may be priced out of that market now given the appreciation 914s have enjoyed lately). Guess I am trying to build a world-class collection of second class sports cars that I lusted after as a kid (should have an Opel Manta on list as well -- loved that flat black hood treatment) :-)

[Mr. Squid]

WOW! Either you aren't married or you have the most understanding wife in the world. But a fun collection for sure.

Your 86 944s will have the electrical speedometer, but the early cars (Pre 85.5) with the POD style gauges are mechanical. The 87 924S has the early style interior, hence the cable. I guess I mention the wheel as you can take it off easily and make sure the cable is poking through and connected. Its simple to remove the cluster, or possibly reach up behind the cluster and push the speedometer out (just held in with pressure). You will have to unscrew the cable from the back of the speedo to remove it fully.

Usually if the temp gauge is having electrical issues it jumps, is inconsistent, or is pegged in one direction or the other. It's ok for temp gauge to cycle as the thermostat opens and closes or when the fans kick on. My guess is one or both of your fans aren't working.

Generally the cooling systems are good when they are up to spec. My personal opinion is being in Texas I would want the lower temp fan switch and a thermostat to match. In other words make sure the thermostat is opening to keep the temps low before the fans kick in.

[Mr. Squid]

https://www.pelicanparts.com/catalog/SuperCat/0991/POR_0991_WATPMP_pg2.htm#item6

[austinporsche]

Thanks, Squid.

Link you posted has a cooling fan switch and an auxiliary cooling fan switch. One has a temp rating, other doesn't. If fans' aren;t running should I replace both?

And do the fans continue running after the engine is turned off? If so, then probably best way to test fans is to get it up to operating temp, then turn off and see if fans are still going.

Guess I am going to have to break down and buy a Haynes for the 924 as it is sufficiently different from the 944.

Lived in Back Bay for 7 years, never had a car the whole time, so making up for it now.

Wife doesn't know about all of them. One in particular is slowly driving her nuts I think: the identical silver Insights. Had one, the automatic, that she could drive but hated it (too slow) and only takes for absolute emergencies. I picked up the manual Insight right off the side of the road -- literally. A guy was selling it because the IMA/Battery light came on, and Honda quoted $4K to replace it. Gave him $900, thinking it would be a donor for my automatic, but then reconditioned the battery with a grid charger for about a week, and now it is better than the automatic I spent $5,000 for. Have spent about a year now leaving one at home and the other around town where my wife was sure to see it -- especially at bars on her way home from work -- and when she'd get home and see the other in the driveway, literally thought I had beat her home or was in two places at once. Once the opportunity presents itself, I am getting ready to pull a plug wire on her Saab so she'll need to ask for the keys to the Insight, but it will be the manual in the driveway, not the auto. She'll get in and go "what the f&%k" and come running back into the house, to which I'll tell her, "oh, sorry 'bout that, I was bored last night, so I decided to swap out the automatic transmission for a manual just to see if it would run better". Best $900 I ever spent on a practical joke.

[Mr. Squid]

Great Practical Joke.

I thought the haynes manual covered all generation 944. Early 944 is the same as the 924S mechanically speaking. Don't get a haynes manual use this Clark's Garage Home Page click on Garage Shop Manual - Your new bible! Should help you diagnose the cooling issue


Aux Fan Switch is the one you want 75 degrees. One fan will continue to run after the car is off depending on temp.

[onZedge]

My similar issues and "solutions":

Speedometer bouncing at low speeds with occasional odometer operation issue.
Not the cable. The main drive plastic worm gear set inside the speedometer is stripped (unfortunately not the more common odometer drive gear fix). Displays speed but only occasional odometer movement.

I will get around to fixing it as soon as somebody volunteers to send me a free donor speedometer to scavenge.

Temp Gauge reads hotter than normal, and fans cycle more than expected issue (radiator was also leaking).
All done at the same time:
a) Replaced radiator with exact aftermarket replacement (LRO Germany; excellent build quality, but I bet it was made in China). Reused the 3-year old fan temperature switch.
b) Replaced Thermostat (I have had 50% success rate history with thermostats - Wahler and "Porsche OEM" versions).
c) Replaced the original 30 year old temperature gauge sender. There was corrosion forming (likely due to weeping) where the threaded body and thermowell are crimped.

Temperature gauge needle is rock steady mid scale except when in bumper-to-bumper traffic, and then only goes up to the 3/4 mark when the fans kick-in. Fans now cycle as expected.