crimony

Currently trying to diagnose a coolant level sensor fault (fast blinking temp gauge) and a persistent minor coolant loss issue.

In an effort to isolate the fault to the coolant level sensor (the light blinks even with expansion tank level up to "max"), I disconnected the sensor. Tight space combined with large hands resulted in eventually disconnecting the cable but I have rotated the sensor in the tank a little.

Since then the coolant loss seems to have increased and I think it's getting out primarily around the sensor.

Can someone let me know which way the sensor connector should face? Is it directly towards the rear of the vehicle? Mine is currently at about 5-o'clock (looking from the top with 12 straight forward).

I tried to rotate it further clockwise but don't want to break it if shouldn't be going that far around.

The sensor appears faulty so I'll replace it next week, but in the meantime I'd like to try to arrest some of the coolant loss if I can.

Thanks.

Cosmo Kramer

I just replaced my coolant tank, and if I remember correctly the sensor only goes in one way. Just push it in and rotate to lock it.

fpb111

DBJoe996

If you click on the Part #2 in this diagram (click on the blue part number) it will show you the bayonet part of the sensor. The sensor is not open to the coolant, so it cannot be where your leak is....unless the tank is cracked where the sensor fits in the coolant tank.
http://www.autoatlanta.com/porsche-p...section=105-20

crimony

This is great info and resolves many questions in my mind.

So if the sensor is loose, it won't affect the cooling system pressure, that's good news.

I'm guessing then that the sensor is a N.C. reed switch, and when installed is adjacent to a magnetic float in a slot on the other side of the tank wall, so when the level is correct the magnet floats up, lines up with the reed switch and opens the circuit. With the sensor disconnected the circuit is open and the light does not flash.

The persistent low coolant warning could then be either the sensor itself faulty or the float is stuck at the bottom of the slot. I'll pull the sensor and check continuity with and without a magnet in proximity to the reed switch.

My tank looks quite new, for a 1998 vehicle it is very white with no yellowing. The 3.4 motor was rebuilt in 2011 with a short block recon "big bore" 3.6 with Nickies and forged pistons. Over AU$25k was spent (previous owner before last), I'm guessing they likely replaced the tank then. Since then the car has done about 25,000km.

The motor was out again last year (to pin the drive sprocket to the IMS - there's a thread about that) and the car returned to me 6 weeks ago, since then the coolant seems to have been problematic. Perhaps something has not been tightly fitted during re-assembly and is the cause. I have a warranty on the recent work (AU$15k) so I think I'll take it back to the shop, hopefully it's something simple.

Thanks all for your help.

Porschetech3

Another point of interest is that your car is a 98 model, all 996 built before Feb 99 were more prone to false illumination of the low coolant warning (blinking). There was a TBS and a new desgin coolant tank with better baffling to help with coolant slosh that caused the false warning. If your car has the original coolant tank, the false warning could be due to coolant slosh and will not go out until the key is cycled, All new tanks are of the revised design.

crimony

Yes in the ~2,000km I have put on the car that has happened to me two or three times. This time it has been persistent, surviving over key-out restarts.

Leak was worse this morning so drove straight to the shop, pressure test revealed expansion tank is split near the top. They're shipping one from interstate and fitting it Wednesday. I got the OEM / aftermarket one as the genuine one is nearly AU$1k. Also I ordered a new level sensor so they'll fit that to the new tank before it goes in.

This will likely tip my total post-purchase expenditure (since September) over the AU$20k mark.

dan_189

1k AUD for the part alone?? I paid $800 installed including the tank, labour and new coolant from the dealership here in Melbourne last year (from memory, might have been the year before).

Who's doing the work? If you give me the part number of the tank you're after ill lookup the dealership part price in AUD for you.

crimony

Got my shop to procure an aftermarket tank (the genuine item was AU$1250, thanks @dan_189 for the info), Wednesday (yesterday) lunchtime took the new level sensor I bought with me for them to fit to the new tank, and went to get some lunch while they worked.

Got a call 90 minutes later, new tank is leaking around the level sensor, will need to procure a second one, should be there Friday, pick the car up in the PM.

Another call today at lunchtime (Thursday), new tank missed the overnight courier so won't be here until Tuesday (Monday is a holiday).

Too bad for my long weekend away with the wife, leaving the kids at home. Two strikes on that front for this car so far, couldn't take it to her end-of-year work function in the hills last year either due to the engine being in pieces in the shop. Grrr.

dan_189

Anytime, happy to help

Gah! Shame about the tank!

Not cool that the new one leaked straight away and knocked out your long weekend plans!!