[Solved] V35 Engine Overheating when stopped or in slow traffic

[Ghostfox]

Thought I would share my story as it’s the second time I have had this fault and a quick google shows it to often be misdiagnosed or the suggested repair is massively overpriced.

 

This one seems to be a very misunderstood problem as this happened while on the way back from a dealership service and they had completely missed the problem with the car. I was driving while in congested freeway traffic and noticed the engine temperature was climbing well into the redline. I had to nurse the car through some careful manoeuvres to force cool air into the engine bay. Luckily traffic cleared up and once up to normal freeway speeds the temp dropped down again but it was clear the temperature was related to vehicle speed and stopping at traffic lights had it shooting up again quickly.

 

This is the second time I have had this fault so diagnosis and repair was relatively quick and painless but I know from the first time I has this issue that the normal service technicians often completely miss the root cause and will recommend expensive repairs that only fix the problem by chance rather than knowing what they are doing, the fixes are often also expensive and require parts that are in fact perfectly serviceable on the car.

 

The fault lies in the engines electric cooling fans, the brushes in the fans have become stuck due to dirt fouling the action and they are no longer making effective contact with the commutator. With 4 brushes inside the motor there is some level of redundancy but after a while the motors become less and less effective until they are not functioning at the required speed. The fans will still turn but they will not reach full speed and will not draw the required air across the radiator, most service techs will just see a spinning blade and assume the fan is working.

 

The simple fix for this problem is to remove the fan housing from the motor, a simple job with plenty of how-to’s on YouTube, and then disassemble the electric motor housings. While not intended to be user serviceable, the housing can be opened with a screwdriver and/or some pliers. Between the 2 motors you will most likely find several of the brushes have become stuck with the spring pressure no longer enough to overcome the dirt and fouling accumulated in the motor. All you need to do is give everything a quick clean and maybe a little lubrication if you have the correct products. The hardest part is the reassembly, I recommend using sowing needles and thread to retain the brushes when you close-up the motor housing. Crimp the housing back together and reassemble and reinstall the fans.

 

All up the fix takes about 2 hours using only a screwdriver, pliers, a shifter, a drain dray and a rag. No new parts required, and the repair should last you another 2 to 3 years before having to repeat the process. This of course presumes the brushes are in serviceable condition, not cracked to worn but even then, the replacement brushes are cheap and simple enough to replace with a soldering iron.

Edited November 15, 2018 by Ghostfox

[niZmO_Man]

Good first post. Usually fan and cracked radiator are the first things I'd suggest to look at. The older RBs have clutch fans so are quite easy to check, but of course electronic fans are harder.