2006 BMW 325i overheating :-(

Hi all, I am looking for some expert advice as I am not very knowledgeable with cars…

I drive a lovely BMW 325i, but it’s getting a little old (2006) with 140k miles on the clock.

Recently if I start-up and jump straight on the motorway, the temperature quickly spikes and the red light comes on.

I usually pull-over and it quickly cools down and then fine for the rest of the day, and sometimes I’ve carried on (waiting for a layby) and it quickly drops back to normal temperatures.

Earlier this week it happened and I quickly flicked the bonnet to find fresh coolant all over the tank, so clearly looked like a leak in the tank.

A local garage pressure tested the tank and said it’s fine so must be the head-gasket – but we put sealant in and it’s still happening…

It only happens in the mornings if I jump straight on the motorway, if I run the engine for 10mins before setting off it’s fine.

It’s really hard to tell where the coolant is coming from, not sure if the leak is the problem or overheating itself…

Anyone had this before? Any ideas on how to diagnose it?

Thanks in advance

Sealant is not likely to cure a leaking head gasket. You need a better mechanic who will check for the byproducts of combustion in the coolant and do a compression test of the engine.

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Thanks for the quick response - much appreciated.

I forgot to add a photo to my original post;

Could the head gasket cause a leak like this?
Looks like the tank to me, but I’ve been assured it’s not… :thinking:

A leaking head gasket will over pressurize the coolant system. Coolant will leave at the weakest point.

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These cars have known problems with their water pumps. Impellers made of plastic that degrades over time. I’d suggest a new water pump, thermostat and a coolant flush but first, a compression check of the engine to try and diagnose a bad head gasket, or not.

A good mechanic would have already done a compression test.