Replacing Coolant Temp Sensors

**3forty8** · #1 01-26-2009, 04:06 AM

I asked fatbillybob how to replace the coolant temp sensors, and he indicated removing the intake plenum was a good way to get at them. I figured that might be a little over my head, so I tried a different method that doesn't involve removing the plenum; follow my folly at your own risk.

Our 348's have two coolant temperature sensors (one for each bank/ECU). The sensors are under the intake manifold, and the coolant needs to be drained in order to replace them; the air filter box also needs to be removed. I won't go into detail on those procedures as they are well documented on this site.

OEM sensors are Bosch units and there are many other brands that are interchangeable; they run about $20 from your local auto parts store whether Bosch or an alternative brand.

On level ground, apply the parking brake, disconnect the negative battery terminal and then jack the rear of the car up enough to remove the rear wheels. Once the car is secure on jackstands and the front wheels blocked, remove the rear wheels, remove the front portions of the wheel well liners and drain the radiators. Then remove your air filter box.

Step 1: Locate the black electrical connectors under the intake plenum and unscrew them; using a 10mm wrench, remove the brackets that hold them onto the plenum (pics 1 & 2).

Step 2: Remove the throttle cable (pic 3).

Step 3: Remove the electrical connectors from the oil sending unit; there is a wide blade and thin blade, so you won't mix these up when re-assembling. Using a thin 24mm wrench, unscrew the oil sending unit and remove it (pics 4 & 5). Now you should have enough room to get your hands under the plenum for the rest of the procedure.

Step 4: Unclip the connectors to the temp sensors; using a 6mm socket loosen the hose clamp to the hose between the sensors (pics 6 & 7). **Place an absorbent cloth and/or small container under the hose prior to removal as there is still some coolant that will drain out.

Step 5: Using a 19mm deep socket connected to an elbow and 6" extension bar, use your ratchet to remove the old temp sensors. These will likely be tough to remove as some corrosion builds up between the alloy of the block and the brass threads of the sensor. I used a breaker bar for some extra leverage. Also note that a little more coolant will drain as each sensor is removed, as with the hose above (pic 8).

There you have it; reverse these steps to install the new sensors, put the air filter box back in, re-connect the battery and then finish up your coolant flush/replacement.

**rivee** · #2 01-26-2009, 04:50 AM

Very nice writeup. Have never had to change mine.

Why did you have to change the temp sensors? Did they go bad?

**troy_wood** · #3 01-26-2009, 07:01 AM

Eliminating inexpensive variables that could lead to future problems - nice. Thanks for the write-up.

**3forty8** · #4 01-26-2009, 09:37 AM

Quote:

Originally Posted by rivee

Why did you have to change the temp sensors? Did they go bad?

Every few hundred miles I was getting an error code for a temp sensor failure; I would reset the ECU's and it would come back, so I believe they were starting to go bad. And if you are in there to replace one, it's just as easy to do 'em both at the same time.

**No Doubt** · #5 01-26-2009, 10:16 AM

Great write-up for an up-n-coming Stooge!

*now that you've got the old temp sensors out, put an ohm meter lead to one pin and the other lead to ground and record the resistance values (two per sensor and you measure from each pin to ground). Or do these sensors just give one overall resistance reading between their two pins?

Would be good to see your values compared to a new sensor, anyway.

**ernie** · #6 01-26-2009, 11:03 AM

Nice write up Eric!

What part numbers for the temp sensors? Any cross reference?

Also, I'm pointing to the temp sensor on the font of the cross over pipe in the pic. Your technique will work nicely for the rear temp sensors, but if you have to get to the front temp sensor it will be a much bigger pain in the neck, and thus will need to remove the plenum.

Again, nice write up bro.

Long live the 348 Brotherhood!

**No Doubt** · #7 01-26-2009, 11:09 AM

Hey ernie, is that front temp sensor just the device that controls the coolant temp gauge in the cockpit?

**saw1998** · #8 01-26-2009, 11:14 AM

Great write-up, Eric! Thanks! One thing though, Stooges are extremely manly-men who never, ever wear gloves when working on their Ferraris.

**3forty8** · #9 01-26-2009, 11:17 AM

Quote:

Originally Posted by No Doubt

Would be good to see your values compared to a new sensor, anyway.

Good idea - I'll post them up after I get a chance to stick a multimeter on them.

Quote:

Originally Posted by ernie

What part numbers for the temp sensors? Any cross reference?

Your technique will work nicely for the rear temp sensors, but if you have to get to the front temp sensor it will be a much bigger pain in the neck, and thus will need to remove the plenum.

Bosch (OEM): 0 280 130 026
Airtex: 5S1483
Adelco: F1864
Standard Motor Products: TX18
Niehoff: TS25151

There's more than two of the damn things in there, lol! I may be wrong, but I believe the two rear ones deliver the signal to each bank of the ECU and the front one delivers the signal for the temperature guage.

**3forty8** · #10 01-26-2009, 11:25 AM

Quote:

Originally Posted by saw1998

One thing though, Stooges are extremely manly-men who never, ever wear gloves when working on their Ferraris.

That's what I thought - until I hung out with them one day and I was the only one who showed up for the party without his gloves!

**f355spider** · #11 01-26-2009, 01:55 PM

Quote:

Originally Posted by No Doubt

Great write-up for an up-n-coming Stooge!

*now that you've got the old temp sensors out, put an ohm meter lead to one pin and the other lead to ground and record the resistance values (two per sensor and you measure from each pin to ground). Or do these sensors just give one overall resistance reading between their two pins?

Would be good to see your values compared to a new sensor, anyway.

+1. The specs are on the Bosch website, and also in the Ferrari workshop manual. I would only use the factory Bosch part, unless you can be absolutely certain the aftermarket equivalent works exactly the same.

Equally important (in fact MORE important) are renewing all the connector pins and boots in your Motronic wiring harness to ensure the computer is getting all the correct values/information. Stay tuned for an important post on the subject from one of our good friends/tech. This fact was proven to me this past weekend, and I am now convinced of it's benefit.

**No Doubt** · #12 01-26-2009, 02:34 PM

Quote:

Originally Posted by f355spider

+1. The specs are on the Bosch website, and also in the Ferrari workshop manual. I would only use the factory Bosch part, unless you can be absolutely certain the aftermarket equivalent works exactly the same.

Equally important (in fact MORE important) are renewing all the connector pins and boots in your Motronic wiring harness to ensure the computer is getting all the correct values/information. Stay tuned for an important post on the subject from one of our good friends/tech. This fact was proven to me this past weekend, and I am now convinced of it's benefit.

It's a hard and fast rule that *all* Ferrari electrical connections should be cleaned with electrical contact cleaner and then coated with a contact enhancer such as Stabilant 22a.

All of them.

**davehelms** · #13 01-26-2009, 02:38 PM

Quote:

Originally Posted by No Doubt

It's a hard and fast rule that *all* Ferrari electrical connections should be cleaned with electrical contact cleaner and then coated with a contact enhancer such as Stabilant 22a.

All of them.

I no longer agree with this statement.

**No Doubt** · #14 01-26-2009, 02:46 PM

Quote:

Originally Posted by davehelms

I no longer agree with this statement.

LOL! It figures! Come on, out with it. There is something better now?

**3forty8** · #15 01-26-2009, 04:55 PM

Quote:

Originally Posted by f355spider

The specs are on the Bosch website, and also in the Ferrari workshop manual. I would only use the factory Bosch part, unless you can be absolutely certain the aftermarket equivalent works exactly the same.

The part numbers listed above were all indicated as interchangeable on various sites (RockAuto, Kragen, etc.) - you bring up a good point, and the sensors from different manufacturers are all around the same price. The Bosch units are actually cheaper than a couple of the others I listed, and for the sake of a couple of bucks it doesn't make sense to go non-OEM unless there is an availability issue.

Quote:

Originally Posted by f355spider

Equally important (in fact MORE important) are renewing all the connector pins and boots in your Motronic wiring harness to ensure the computer is getting all the correct values/information. Stay tuned for an important post on the subject from one of our good friends/tech. This fact was proven to me this past weekend, and I am now convinced of it's benefit.

When will Dave be officially announcing this and more important, is there a 348 version???

**Llenroc** · #16 01-26-2009, 05:53 PM

Wow!! you have some serious corrosion problems with your cooling system. Look at the pic before you removed the hose between the sensors(bulging hose end) and then look at the pic of the fitting after the hose is removed. I would check out the rest of the fittings where the hoses connect to fittings and maybe do a thorough flush and replace coolant hoses.

**3forty8** · #17 01-26-2009, 06:13 PM

Quote:

Originally Posted by Llenroc

Wow!! you have some serious corrosion problems with your cooling system...

Yep, and what you are looking at is roughly 2.5 years since the last flush, hose inspection, replacement, etc. I think it was Dave Helms (in another thread) who said two years max between changes and looking at it now I'd say even more frequently.

**f355spider** · #18 01-26-2009, 06:29 PM

(quote/nodoubt) It's a hard and fast rule that *all* Ferrari electrical connections should be cleaned with electrical contact cleaner and then coated with a contact enhancer such as Stabilant 22a.

All of them. (quote)

Quote:

Originally Posted by davehelms

I no longer agree with this statement.

Me neither...I was duly indoctrinated last Friday night...and am now a believer. I have found salvation! Hallelujah!

**Llenroc** · #19 01-26-2009, 10:07 PM

Quote:

Originally Posted by 3forty8

Yep, and what you are looking at is roughly 2.5 years since the last flush, hose inspection, replacement, etc. I think it was Dave Helms (in another thread) who said two years max between changes and looking at it now I'd say even more frequently.

Replacing the coolant every couple of years is important but what has really contributed to that problem in the photos is not having hose that fits tight around it's respective fitting and not having the clamp positioned properly. Hose that fits loosely and is shrunk around it's fitting by the clamp is not the way to do it, ie; using Std. sizes when metric is required. I would say those hoses on that engine have not replaced in long time.

**davehelms** · #20 01-26-2009, 10:13 PM

Quote:

Originally Posted by No Doubt

LOL! It figures! Come on, out with it. There is something better now?

Yes, nothing at all with new female connectors, boots and everything properly cleaned.

Hugh F355Spider has now finished with the DYI testing of the kit and in the process resolved a long term headache.

See FerrariAds, it works!