[Lukerogers136]

I just finished up the valve cover job on my e90 n52 and I went to take it for a test drive and it overheated. Come to find out the fuse for the water pump keeps blowing. I think the water pump is still good because it is a fairly new oem one. Does anyone know if this is something simple? Or is it just some small electrical short some where?

[gbalthrop]

Originally Posted by Lukerogers136

I just finished up the valve cover job on my e90 n52 and I went to take it for a test drive and it overheated. Come to find out the fuse for the water pump keeps blowing. I think the water pump is still good because it is a fairly new oem one. Does anyone know if this is something simple? Or is it just some small electrical short some where?

Questions:
1) What are Last-7 Characters of your VIN? OR Build Month/Year?
2) Which fuse is blowing?
3) Have you checked for Pinched wire under Valve Cover?

There are TWO fuses related to Coolant Pump in all E9x models, but which ones they are and WHERE they are located depends upon build date. One of the fuses supplies the control circuit for BOTH Pump & T-Stat. Other supplies Pump Motor.

You will need a Multimeter ($7 HFT/ $10 Amazon) to test. I will provide wiring information and test suggestions if you answer questions above.
George

[Lukerogers136]

Originally Posted by gbalthrop

Questions:
1) What are Last-7 Characters of your VIN? OR Build Month/Year?
2) Which fuse is blowing?
3) Have you checked for Pinched wire under Valve Cover?

There are TWO fuses related to Coolant Pump in all E9x models, but which ones they are and WHERE they are located depends upon build date. One of the fuses supplies the control circuit for BOTH Pump & T-Stat. Other supplies Pump Motor.

You will need a Multimeter ($7 HFT/ $10 Amazon) to test. I will provide wiring information and test suggestions if you answer questions above.
George

The last 7 of the vin is NE25289.
Fuse number is F02 and it is a 30 amp. The 40 amp main waterpump fuse (F07) is fine. There is no pinched wire under the valve cover but I will double check. Thank you.

[gbalthrop]

Originally Posted by Lukerogers136

The last 7 of the vin is NE25289.
Fuse number is F02 and it is a 30 amp. The 40 amp main waterpump
fuse (F07) is fine. There is no pinched wire under the valve cover but I will double check. Thank you.

On early 2007 N52, Fuse F02 not only supplies Coolant Pump & T-Stat Electronics, but ALSO Cam Sensors (2) and
VANOS Solenoids (2). ISTA SSP Wiring Diagram ScreenPrints are attached. If you have the E-box open, where F02 is located,
you can test for Ohms Resistance (relative to Chassis Ground) on Orange wires supplying F02 Voltage to each of those components.

That Resistance measurement prevents expending 30A fuses to test. Since this follows VC Replacement, check for short to ground
in the orange wires going to the Cam Sensors & VANOS Solenoids. A pinched Orange wire is most likely suspect.
Please let us know what you find,
George

[Lukerogers136]

I unplugged each connector 1 by 1 monitoring the ohms and it stayed the same at .04 when monitoring. Then I pulled all of the plugs on the vanos and camshaft and checked all the wires to verify there was no short. Then out of a last ditch effort I decided to plug in the fuse and check if it would blow with everything unplugged. And it still blew. The only observation I have is that the vanos electrical connectors do have oil in them.
Thanks

[gbalthrop]

Originally Posted by Lukerogers136

I unplugged each connector 1 by 1 monitoring the ohms and it stayed the same at .04 when monitoring.
Then I pulled all of the plugs on the vanos and camshaft and checked all the wires to verify there was no short. Then out
of a last ditch effort I decided to plug in the fuse and check if it would blow with everything unplugged. And it still blew.
The only observation I have is that the vanos electrical connectors do have oil in them. Thanks

One of the Orange Wires is in contact with Chassis Ground. If fuse F02 blows when Ignition is turned on, with ALL
6 Component connectors DIS-connected, that leaves the ORANGE WIRES as the cause.

There is a splice: X6964, located in E-box, where the Orange supply wire from F02 is spliced to the 6 Orange
wires that go to the components shown in the F02 circuit supplied earlier. That splice location is NOW attached.

While it would be less work, IF you could visually find a shorted Orange wire (presumably from Valve Cover work), the
ONLY way you can ELECTRICALLY identify the shorted wire is by SEPARATING that splice into 6 Orange wires NOT connected
to each other, and then check for continuity to ground (Nearly 0 Ohms resistance relative to Chassis Ground) at each
Orange wire at component connectors.

Using Ohm's Law (Volts = Resistance x Amps), any resistance LESS than .4 Ohms will blow a 30 Amp Fuse
(12V = .4 Ohms x 30 Amps). You report .04 Ohms which is LESS resistance than .4 Ohms (almost a "Dead Short" = 0 Ohms).
I would carefully inspect the wiring harness going to the VANOS Solenoids & Cam Sensors, and also the harness going down
to the Pump/T-Stat. If that does NOT reveal harness trapped under VC, or otherwise shorted to ground, separating
X6964 is only way I know to identify the trapped/shorted Orange wire.
George

[Lukerogers136]

So i unplugged the connector where the wires are spliced and checked ohms on that side of the system and it was reading 1 (inf) so now I know that I have a short in the fuse box somewhere. I put a fuse in with the x8680 plug unplugged and clicked the ignition and the fuse still blew. Any suggestions?

[gbalthrop]

Originally Posted by Lukerogers136

So i unplugged the connector where the wires are spliced and checked ohms on that side of the system
and it was reading 1 (inf) so now I know that I have a short in the fuse box somewhere. I put a fuse in with the x8680 plug
unplugged and clicked the ignition and the fuse still blew. Any suggestions?

There are TWO (2) connectors between F02 & splice X6964. Those are (1) X8680, which appears to be a 10-pin connector
at the Fuse Carrier for F01-F05, & (2) X60552, an intermediate connector between Fuse Carrier & Splice.

ISTA diagrams showing location & connector view of those two connectors are attached. If you have NOT already done so,
I would suggest:
1) Disconnect X8680 at fuse carrier & test Ohms/Resistance in reference to chassis ground on either socket of F02 (fuse removed)
with Ignition/KL87 (K6300 DME Main Relay) OFF. BOTH Ohm values should be ~ 1/Infinite. If NOT, there would appear to be
a short in the Fuse Carrier. If Ohms reading for each socket is ~1:
2) I would then disconnect X60552 (leaving X8680 disconnected), & measure Ohms at X8680/4, Orange wire going to X60552.
If NOT ~ 1/Infinite, there is a short in the Orange wire between those two connectors. If ~ 1:
3) Measure Ohms in ref. to ground at X60552/2, Orange Wire. If < .4 Ohms, there is a short on the splice/component side
of the Orange wires from X60552.

I have never opened my E-box, so the foregoing is based solely on ISTA wiring diagrams. The concept is to isolate
the area of LOW resistance or short to ground in the Orange wires or fuse carrier, as much as possible. Keep in mind
that there are a few "Ignition-switched grounds" or wires that can short with Orange wires, ONLY with ignition ON.

ADDED Edit: Also attached is SSP wiring diagram of Connector X60552. Note there is a Brown ground wire associated with
the Compressor Valve at socket #5 of that connector. There are occasional reports of internal shorts or contact between
wires in a connector within the E-box, such as between the Orange F02 wire & Brown Y2a ground wire.

If you need MORE ISTA diagrams, please ask.
George