Temp gauge creeps up, but only at motorway speeds, under load

[danmetallic]

Hi all! I’m after some advice. Temp gauge happily sits dead in the centre while driving around at anything under 40mph (incl sat in traffic etc). But as soon as I hit the motorways I’ve noticed the temp needle creeping up pretty high and then gradually returning to centre. Motorway hills will def push it up.

Coolant levels are good and radiator is clear of debris.

Any advice much appreciated. I come from the vintage van world, so I’m pretty sensitive to gauge paranoia


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[Rob_Wood]

Try using a glycol based coolant.
Check the fins in your radiator aren't blocked up with grass sead or other crud.
Is your fan turning properly and at the right time. Also check it's undamaged.
Let us know how you go.

[Philos]

I know this may seem obvious but, check your radiator is full.

Don't just assume if there is coolant in the overflow, your radiator is full.

[danmetallic]

Try using a glycol based coolant.
Check the fins in your radiator aren't blocked up with grass sead or other crud.
Is your fan turning properly and at the right time. Also check it's undamaged.
Let us know how you go.

Thank you for your advice!!! I will double check the radiator. How best to check the fan operation? I’m not so sure I can ever recall hearing it run.


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[danmetallic]

I know this may seem obvious but, check your radiator is full.

Don't just assume if there is coolant in the overflow, your radiator is full.

Thanks. What’s the best method of checking the radiator?


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[Philos]

I know this may seem obvious but, check your radiator is full.

Don't just assume if there is coolant in the overflow, your radiator is full.

Thanks. What’s the best method of checking the radiator?

The radiator should have a cap on the top of it.

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[Rob_Wood]

Try using a glycol based coolant.
Check the fins in your radiator aren't blocked up with grass sead or other crud.
Is your fan turning properly and at the right time. Also check it's undamaged.
Let us know how you go.

Thank you for your advice!!! I will double check the radiator. How best to check the fan operation? I’m not so sure I can ever recall hearing it run.


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Open the bonet while the engine is up to running temp. Stand & watch for the fan to turn. If it's an electric driven fan it can take 10, 15 or even 20 minutes to kick in. If it's belt driven, it should not stop. Also take a really good look at the fan and look for damages, bent blades, dinged or chipped blades, if damaged, replace it.

[Rob_Wood]

I know this may seem obvious but, check your radiator is full.

Don't just assume if there is coolant in the overflow, your radiator is full.

Thanks. What’s the best method of checking the radiator?


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When cold (make sure it is actually cold) take the radiator cap off, look inside for coolant, if you can see some then chances are you're good, some reservoirs however will suck out to below the level of the top tank and still be ok. In this case you can top up your coolant in the radiator and allow it to overflow without any major concerns. This method will equalise over.time.

If after all these things you're still having issues, then consider getting the water pump and thermostat checked, any radiator specialist should be able to help you out with this bit.

[danmetallic]

Thank you Rob! I’ll take a look tomorrow hopefully.


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[greensic]

Sometimes overheating like this can occur of the top radiator hose in a bit old and soft. At higher revs, like highway driving, the top radiator hose can suck itself closed and weaken the cooling process. Lift the bonnet and watch to see if it closes you lift the revs for a while. Its an easy fix if needed.

[danmetallic]

Sometimes overheating like this can occur of the top radiator hose in a bit old and soft. At higher revs, like highway driving, the top radiator hose can suck itself closed and weaken the cooling process. Lift the bonnet and watch to see if it closes you lift the revs for a while. Its an easy fix if needed.

Good tip. Cheers!


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[danmetallic]

Ok, so went out for a drive today and kept a proper eye on everything that was happening.

Gears 1,2,3 and 4, at any speed the temp was fine. Even in fourth and running higher revs, driving at 60mph.

As soon as I went into 5th gear the temp went up, back to 4th (same speed) the temp went down.

To me (at least) this might point to the water pump on its way out maybe.

The other thing that I forgot to mention (because I assumed it was the DPF ejecting) is that I get a cloud of smoke from under the front right wheel arch occasionally when it has been at the higher temps and I then slow down. .

Really hoping it’s not something more catastrophic like engine heads etc.

Normal working day tomorrow so I will try and speak to a couple of different garages then.

Thanks again for people’s suggestions so far.


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[Rob_Wood]

The other thing that I forgot to mention (because I assumed it was the DPF ejecting) is that I get a cloud of smoke from under the front right wheel arch occasionally when it has been at the higher temps and I then slow down. .

Really hoping it’s not something more catastrophic like engine heads etc.

If it is smoke, then possibilities are exhaust pipe or manifold, less likely head gasket. If it is steem (not smoke) then it.could be anywhere throughout the coolant network.