12 replies to this topic

[JamesMiniMealor]

Ever since I've had my cooling system sorted (new expansion tank + official cap, new bottom hose, flushed the system, no airlock), the car can't seem to cruise at over 70mph on flat ground.

 

The temperature rises well past half way if I try cruising at 70mph, or lower speeds if I'm going up hill. At one point when driving up a hill in Wales at full throttle, 40mph ish, the temperature almost went into the red and I almost had to stop.

 

Any suggestions? The car never really overheated when going 80mph ish when the expansion tank and hoses were all leaking and boiling over! 

 

- the engine fan does come on when it's supposed to

- turning the heater on doesn't stop overheating

- the expansion tank liquid does not boil

- no obvious leaks in the system

- never any problems when idling or driving below 50 ish.

 

NB I am not a car expert in the slightest

[neal]

When the cooling system was overhauled, did you manage to clear the airlocks in the system quickly when the engine was run up to temperature?

Did you change the thermostat for a new one when you overhauled the cooling system?

Is the water pump in good condition?

I take it that you get hot air through the heater matrix and you are 100% sure that there are no airlocks hiding within the system?

You said that the temp rises way past the halfway and almost into the red at times, can you rely on what the temp switch and gauge is telling you?

Sorry for asking these questions, but these all need to be considered especially as the engine appears to overheat when under load and/or high revs.

Edited by neal, 08 October 2016 - 11:11 PM.

[JamesMiniMealor]

When the cooling system was overhauled, did you manage to clear the airlocks in the system quickly when the engine was run up to temperature?

Did you change the thermostat for a new one when you overhauled the cooling system?

Is the water pump in good condition?

I take it that you get hot air through the heater matrix and you are 100% sure that there are no airlocks hiding within the system?

You said that the temp rises way past the halfway and almost into the red at times, can you rely on what the temp switch and gauge is telling you?

Sorry for asking these questions, but these all need to be considered especially as the engine appears to overheat when under load and/or high revs.

 

The bottom hose was replaced by a mechanic that specialises in Minis. He obviously refilled the coolant after he did it, and told me the correct way to do it to prevent airlocks. The heater is nice and hot when the engine is warm.

 

I don't know the condition of the water pump or accuracy of the temperature gauge - how can I test these? 

 

Like I said, the temp only rises when I'm going at speed, or particularly when I'm at or near full throttle. I've got no reason to distrust the temp gauge. It reads cold when I start the engine up, slowly rises to the midpoint after a few minutes and stays there unless the engine is being pushed harder. 

[neal]

When the cooling system was overhauled, did you manage to clear the airlocks in the system quickly when the engine was run up to temperature?

Did you change the thermostat for a new one when you overhauled the cooling system?

Is the water pump in good condition?

I take it that you get hot air through the heater matrix and you are 100% sure that there are no airlocks hiding within the system?

You said that the temp rises way past the halfway and almost into the red at times, can you rely on what the temp switch and gauge is telling you?

Sorry for asking these questions, but these all need to be considered especially as the engine appears to overheat when under load and/or high revs.

 
The bottom hose was replaced by a mechanic that specialises in Minis. He obviously refilled the coolant after he did it, and told me the correct way to do it to prevent airlocks. The heater is nice and hot when the engine is warm.
 
I don't know the condition of the water pump or accuracy of the temperature gauge - how can I test these? 
 
Like I said, the temp only rises when I'm going at speed, or particularly when I'm at or near full throttle. I've got no reason to distrust the temp gauge. It reads cold when I start the engine up, slowly rises to the midpoint after a few minutes and stays there unless the engine is being pushed harder.

I wish I was hanging over your engine buddy to check it, was the thermostat replaced?
I would suggest that you take the car back to the guy who specialises in minis and explain the problem and that you don't understand why this is happening and as you said that the overheating was not an issue before you had the items replaced.

I assume that you have paid for this service? If it was me I'd be definitely taking it back.

Edited by neal, 09 October 2016 - 12:09 AM.

[MacGyver]

Agree with taking it back, sounds like you have insufficient water circulation at high revs or under load.
Either the pump is not pumping hard enough or like it was said the thermostat is not opening right.
It could also be the rad being partially blocked too, did it get back-flushed and checked?

[Steve220]

Sounds like the radiator isn't providing sufficient cooling

[Midas Mk1]

Gauge / temp sender? I know mine on my MPi can be right temperamental sometimes

[neal]

What worries me is that the 'mechanic who specialises in minis' should know how problematic these little buggers can be especially when the vehicle presented to him was (quote) 'when the expansion tank and hoses were all leaking and boiling over'

Regardless of what vehicle you have, when you carry out any repairs there is a process to follow and plenty of checks (as mentioned above by all) so things like this don't happen,
It could be just one little thing that is causing the problem but to be fair all should have been checked prior to letting you have the car back.


I would tread carefully when returning your vehicle and listen very carefully to what the chap says and bear in mind we all make mistakes, BUT... If you have a gut feeling that does not settle with you then you might be better off finding a new mechanic.

I only hope that it hasn't caused any other damage to your vehicle, good luck!

[Fast Ivan]

does the fan come on when this problem happens?

[neal]

does the fan come on when this problem happens?

Good point and can now see where you are going with this, but I didn't bother to ask that one as he said in his first post 'The engine fan does come on when it's supposed to'

Thinking about this though; Does the fan cut/switch off even when the temp gauge is high or does the fan cool the engine where the temperature needle drops a fraction but is still higher than it normally would be? Also have you noticed if the fan stays on for longer than before the problem began?

Edited by neal, 10 October 2016 - 05:31 PM.

[JamesMiniMealor]

The mechanic doesn't seem to be a con man and he's always busy. He's very cheap though and better than other places I've been.

 

I've been going to get the car fixed constantly every few months (always different problems) and I can't be arsed taking it back.

 

How do I test a thermostat? How do I check the radiator? It has been back flushed or whatever. 

 

The fan comes on and stays on until the needle is at the midpoint. 

 

Like I've said, the problem only occurs when climbing mountains or cruising at 70+mph so it's only somtimes an inconvenience. I have plenty of time to learn how a cooling system works 

Edited by JamesMiniMealor, 10 October 2016 - 10:03 PM.

[pete l]

It looks like you are going to have to take everything apart and check nothing is blocked or restricted and that the thermostate is working correctly.

 

Check the water pump too.

 

Pete

Edited by pete l, 11 October 2016 - 01:01 PM.

[tmsmini]

If you can, I would verify the temperature. In the US, the laser aimed temp sensors are pretty cheap, maybe not the most accurate but it would allow you to verify the actual temperature.

If the heater warms up, you are at least getting some coolant circulation.

 

On an MPi, changing the water pump is relatively easy. Do you know when it was last changed or how many miles since it was changed?