Bit of help with a dodgy fuse box MK5 Golf

StanwithaPlan

I posted a little while ago and my car has now had a service and for two days it was running beautifully!

Now an old problem has returned and the RAC had to rescue me today as the engine management computer said NO!

In March I had a fault, engine management turned the car off and I had to get towed to the garage. They changed the coolant temperature sensor, the car had been drinking quite a bit of coolant but no other signs of gasket failure, oil and water were and still are clean.

They changed the sensor and the coolant consumption went down (to only needing topping up once every few weeks instead of once every few days) It has been pressure tested 3 times by different garages and no one found a leak in the coolant/radiator system,

In the last few weeks the coolant consumption has gone back up and the fan has been going more than usual. The car has never overheated - it tells me as soon as I start the engine if it needs coolant and I top up before driving off.

Tonight the engine management cut the car out and my new RAC membership came into its own! Nice RAC man thinks there is a problem in the wiring or fusebox as a relay was making a hideous noise when the ignition was on and the car wouldn't connect to his computer. The relay itself looked ok but he could see that there had been moisture in the fusebox and there was some corrosion where the pins to the noisy relay went, or that the wiring further back was dodgy.

It will go to the garage to check it's not a dodgy sensor but I think it's more likely he is right and there is an issue with fusebox or wiring, in which case I think firstly I will replace the fuse box and hope the problem isn't further back in the wiring:(.

My question is...sorry it took a while to get here!...could the coolant be escaping and causing the moisture in the fuse box? He couldn't work out why it had been damp in there and now I wonder if the two are connected? I may be totally off track but seems a coincidence? Problem is if that isn't where the coolant is going, I'm stumped as to why it's disappearing!

Help! x

forgotmyname

How is the wiring or a dodgy sensor causing the loss of coolant?

Your water must be going somewhere. The engine management maybe cutting the engine out because its overheating.

Are they pressure testing it when hot or cold?

Sister had a MK1 diesel focus. When on the motorway it would cut out. It was a used vehicle but only a couple of years old and not long bought it.

Took it back 3 times. Always happened on the motorway. 3rd time i went with her to pick it up. Called the mechanic to take us to the car. Car warm almost cold. Slight warmth to the exhaust manifold.

Unscrewed the expansion cap and hisss....... I asked him Is that normal then...
Eventually she got the headgasket done. Problem sorted.

StanwithaPlan

its been tested hot and cold - still no leak in the system and no other signs of gasket failure...I'm not ruling it out - just wondered if one issue could be causing the other?

DUTR

StanwithaPlan wrote: »

its been tested hot and cold - still no leak in the system and no other signs of gasket failure...I'm not ruling it out - just wondered if one issue could be causing the other?

Not likely really, the fuse box is at the side of the dash where you open the driver's door.
If the heater matrix is leaking, you would have residue on the interior glass.

StanwithaPlan

DUTR wrote: »

Not likely really, the fuse box is at the side of the dash where you open the driver's door.
If the heater matrix is leaking, you would have residue on the interior glass.

Sorry I should have said, its the under bonnet fuse box next to the battery - again, I don't know if that makes a difference, just wondered if any part of the coolant system ran around it which could have caused the moisture and which would hide a leak when pressure tested?