My Mazda gets hotter as it gets faster.. - stunorthants
My Mazda has developed an issue with the cooling which ive never experienced before.

In normal driving the temp gauage sits just above half, but today when I took it up to 70mph for about 10 mins, it went up to just below the red before I slowed down. However, slowing down to 50mph an dteh temp crept back down to normal.
I then did 70 again and it went slowly back up.
In traffic, its normal and up to about 60 it stays normal, but then gets hotter when I get up to 70 for prolonged period.

Ive replaced the bottom hose and radiator cap in the last month but thats the only changes. i would say that this was prob firsttime ive done 70 for more than a few mins so maybe not related to the new parts.

Any clues?
My Mazda gets hotter as it gets faster.. - DP
This is normally due to the coolant not circulating properly - either though an airlock, duff thermostat or other restriction. I'm still chasing air out of the Mondeo's system after changing the water pump 2 weeks ago. It does what you describe, only maybe not quite to that extreme.

Have a feel and check all the hoses (plus the radiator itself) get uniformly hot when the engine is at running temperature. Obviously subject to health and safety precautions.

Cheers
DP
My Mazda gets hotter as it gets faster.. - Number_Cruncher
It might be worth checking for blockages in the radiator, restricting the flow of coolant; sticking thermostat, and a failure of the water pump impellor are other possibilities.

Number_Cruncher
My Mazda gets hotter as it gets faster.. - stunorthants
I get the feeling it may have had radweld put through it at some point as there was some brown gunge under the old radiator cap - should I flush it through and stick a new thermostat in, see if it helps? That would be a cheap job.
My Mazda gets hotter as it gets faster.. - jc2
Doesn't have to be radweld;could just be sludge,rust,foundry sand or whatever;a flush with water or chemical can only do good(tho' on one of my cars it did show up a cracked water-pump).
My Mazda gets hotter as it gets faster.. - stunorthants
May seem like a silly question, but when I refill the radiator, how much do I put in? Do I just fill it to the top?
My Mazda gets hotter as it gets faster.. - cheddar
Make sure you have coolant/anti freeze in it and not just water, coolant restricts corrosion, reducing the risk of freezing in winter and, importantly, conducts heat better than water alone.
My Mazda gets hotter as it gets faster.. - stunorthants
Yeah I know, I worked in a service department for quite a while, just never picke dup much of the actual techinical knowledge!

I just wanted to know if I fill the radiator up to the top when I refill?
My Mazda gets hotter as it gets faster.. - Dynamic Dave
I just wanted to know if I fill the radiator up to the top when I refill?


There *should* be a max marking somewhere on the header tank. Fill only to that mark.
My Mazda gets hotter as it gets faster.. - stunorthants
Ive booked it into my local garage - he is gonna drain the cooling system, flush it, change the thermostat and refill with correct concentration of coolant for £25. Saves me doing it eh!

He also agrees that its poor flow round the system and should be easy to cure.
Mazda Cooling update... - stunorthants
Here was my original post: {Now moved to that post as it's related to it - DD}

'My Mazda has developed an issue with the cooling which ive never experienced before.

In normal driving the temp gauage sits just above half, but today when I took it up to 70mph for about 10 mins, it went up to just below the red before I slowed down. However, slowing down to 50mph an dteh temp crept back down to normal.
I then did 70 again and it went slowly back up.
In traffic, its normal and up to about 60 it stays normal, but then gets hotter when I get up to 70 for prolonged period.

Ive replaced the bottom hose and radiator cap in the last month but thats the only changes. i would say that this was prob firsttime ive done 70 for more than a few mins so maybe not related to the new parts.'

I took the advice given and replaced the radiator cap, thermostat, had the cooling system drained, throughly flushed through and new coolant put in.

This has cured the overheating and my mechainic said that the radiator was very clean, but the engine itself was quite sludged up, most likely the cause of the overheating.

However now, the car runs very cool, more so than normal, so im wondering if this is ok?

Normally the temp gauge goes to exactly half way and the fan cuts in about 3/4 up the gauge.

Now the car barely manages to get to 1/3 unless in stationary traffic where it goes up to just below 1/2 and then the fan cuts in and it drops back down.

Really I was just wondering why this would be and if it is ok to leave it as it is? I know its not overheating whichis good, but Id be interested to know the mechaincs of why it doesnt get to the normal temp.

I took it on a 15 minute blast at 70mph and it didnt heat up past the normal so the original issue certainly has been solved.

Many thanks for any help!
Mazda Cooling update... - Glaikit Wee Scunner {P}
I'd expect the temperature gauge to get to 1/2 way in normal running and stay pretty static.

To be honest it sounds like the thermostat is missing or not the correct one.
Are you sure a new one was installed after the flush through?
--
I wasna fu but just had plenty.
Mazda Cooling update... - jc2
If you have air-con the heat from the the air-con rad. may be too much for your normal cooling system.ie. the hot air from it may overload your normal system.
Mazda Cooling update... - stunorthants
The thermostat was a Mazda sourced one, definatly the right one. It doesnt have aircon no.

is it much of an issue if the car doesnt get up to full operating temperature? It certainly runs well enough.
 

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