Oil and water temperature gauges have stopped working

328 US version. So that I don't go down a wrong path again, the only thing I have done recently in the engine bay is to remove the water header tank so I could take off the additional air valve to check it (was OK). There are some wires in the vicinity but I am not seeing anything wrong that is obvious. Does anyone think I could have disturbed the feeds to the gauges? Otherwise I am not sure how both could stop working. There are two connectors onto the thermostat I did label these so they are not reversed. I hope.

 

Yes, the two temperature gauges both not working. Other gauges OK including the clock. Maybe a clue - I don't know what is normal behavior - but when they were working it would always take some minutes (at least five, maybe more) for the water temperature gauge to start moving, and then it would go quickly to a mid position on the gauge. This was long after the header tank was warm. But what always seemed a bit strange to me is that the oil temperature gauge would move at the same time. Well indeed, perhaps this is some grounding issue near the gauges, or perhaps even that there is short between the two signals.

 

Apologies, I have been fooling myself, and after 3 months of not using the car (replacing suspension bushes) I am clearly not remembering well. So I just did the experiment of starting from cold, and holding at 2000 rpm. After 10 minutes the water temperature gauge starts to move. After 15 minutes it is at 170 deg. The oil temperature gauge also starts to move up slowly after 10-12 minutes and gets to around 170-180 deg or so. I don't recall it taking so long but never bothered to actually measure the time. So I am assuming all is OK - at least the gauges are working...

 

Thanks for all the other useful information! However it is indeed warming up much slower than it used to, plus the engine is very down on power as I discovered this morning after finally getting the car out of the garage, and then having trouble getting up the hill from my garage to my house in first gear... So either something happened while the car was slumbering in the garage while I did the suspension bushes, or else I have inadvertently knocked something while doing the job.. It also now does a "soft fart" when being switched off, not a real backfire. Idles at 1000 rpm. I will start being a bit more systematic in troubleshooting now. There are some strange things with this car, like the pressure out of the right exhausts is more than the left pair, although when starting up the left is hotter. I thought this is "normal" and a function of the (US with cat) exhaust system, but maybe there is a block? Nothing would surprise me, after removing a very well made mouse nest (dating from the previous owner) from under the brake fluid container! And this on a car in really nice condition, history file from almost new, that I bought from a Ferrari Main agent..

 

Yes!! I replaced all the spark plugs with the NGK iridiums, before getting my timing light out. And indeed the front bank is not firing nothing when the sensor for the light is put on the wire from the coil to the cap. What threw me off the track is how smoothly the engine idles using one bank, given that my old Mustangs are horrible in such a situation, this is the difference between a flat plane and a normal crank I suppose. Reading old posts there is a confusing discussion on whether this fault could be caused by the crank annular sensor a/o the TDC sensor. But I gather that's a possibility for 308s and not 328s, so that would point at a failed coli or a short at the cap/rotor. Or an issue with the other coil connections The coils look old. The HT wires are relatively new, with few miles. Not sure about the caps, they look OK externally but I don't see them mentioned in the invoices, that go back to 1998.

 

End of story I hope - I bought a new coil including power module from Superperformance, they describe it as Magneti Marelli but it isn't its a Bosch, it even has a label attached saying "Germany" which some might believe... I notice that US suppliers I looked at add a $500 core charge, refundable if you return your old coil, they want the heat sink. But since the Bosch unit doesn't look like the original coil, I transferred only the power module, and all now works! BTW the EBay power modules most/all say made in China, and are suitably cheap... And, given that it seems that all the usual suppliers I looked at describe the Bosch coil as "approved", I suspect that the original style is not available new, although Maranello will order it for you from the factory with delivery time maybe infinity. Eurospares have second hand coils at a reasonable price.