bus overheating

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Brisbus

bus overheating

Post by Brisbus »

I have a MAN 34 seat ex Murrays bus that over heats to 120 degrees travelling at 100 kph on the highway but runs at the right temp of 80/90 degrees when stop start around the city. Radiator has been flushed and cleaned, compression test was ok, water pump has been replaced and compression test on engine showed up ok as well. Engine is running ok. Has anyone ever come across something like this or have any suggestions as to what might be the problem ?
bagmaker
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Re: bus overheating

Post by bagmaker »

restricted airflow through radiator?
eg- air being diverted away from where it should go at speed
slipping belts, blocked radiator
or
coolant restriction within system
eg- blocked radiator internals
dodgy thermostat
collapsing supply hose

how does it go on a long hill?
that test would isolate the airflow to the radiator problem
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boronia
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Re: bus overheating

Post by boronia »

Possibly the belts could be slipping at higher revs
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CCCC
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Re: bus overheating

Post by CCCC »

Is the fan viscous type , can you lock the fan in and take it for run at 100km/h , if its running at normal temp it could be the viscous needs replacing.
Could also try a side scoop to suck in more air , has there been any panel work or grill work done from original manufacture to interfere with airflow.
From memory the 420hp MAN's had electrical fans ,there was an electrical plug near radiator , if you pulled out the connection the fan would go onto high speed mode.
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DiAmOnD T
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Re: bus overheating

Post by DiAmOnD T »

Not sure on your bus, but the 16.240's had a two speed electric motor to control temperature. If your bus has this it may not be operating stage two (hi speed fan)
Just a thought
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boronia
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Re: bus overheating

Post by boronia »

I think he is talking about a 12.190.They were the only MANs Murrays operated.
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DiAmOnD T
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Re: bus overheating

Post by DiAmOnD T »

Ah ok Thanks
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