Diagnosis makes no sense

glenman1966

glenman1966

glenman1966

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Joined
29 Feb 2024
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9
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Up north
Recently car is overheating after about 15mins,if driving fast,ie motorway,heating sometimes works,then dosent,then needle starts climbing,additionally alternator pulley is faulty,metal shearings can be felt,when putting hand in,on leaving it into garage,was told need a new alternator,fair enough,but when i asked about car overheating,he said replacing it would cure heating problem, surely given that my water pump is driven off the timing belt(vectra ctdi )this wont be the case
 
Rilot said:
Are you sure it's driven off the timing belt? That would be very unusual for a water pump. They are nearly always driven off the accessory belt.
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Be the first to admit my car knowledge is limited,but everything ive read on vauxhall vectras seems to say this is the case,i could well be wrong,as not very well versed in car matters
 
yes over-heating sounds unrelated to alternator - no bad noises to indicate water pump might be going ?
otherwise thermostat sticking open to prevent initial cabin heating, erratically closing causing over-heat - or, if overheat happens when you get off motorway ? aux fan on radiator - if it has one.
 
My vectra would have a heating blip every now and again and just knocking the heating knob down a touch and then back up to full would get the heat flowing. I put it down to a stuck flap somewhere letting more cold in than it should.

As mentioned by a few posters, the water pump is definitely driven by the cambelt on the CDTi engines.

I'm not sure the two issues are related though and I think you've got 2 completely different issues. A coolant change and beeld might be worthwhile if you can confirm your cooling fan is definitely working OK.

Edit: I have read that the propellor shaft on the water pump can stop working properly so only part of the engine is cooled correctly. E. G. It isn't pushing the water fully or it doesn't spin 100 percent so the temp can rise and fall as it does or doesn't work.

Never did enough research on it to confirm though but could also be a faulty temp sensor too.
 
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jpaul said:
yes over-heating sounds unrelated to alternator - no bad noises to indicate water pump might be going ?
otherwise thermostat sticking open to prevent initial cabin heating, erratically closing causing over-heat - or, if overheat happens when you get off motorway ? aux fan on radiator - if it has one.
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Fans working fine,as can hear them shutting down,no noises,other than most recent problem with pulley,overheating problem preceeded,the alternator problem,like say seems to manage,when theres not much demand on engine,thermostat warning light has come on twice,on the longer journeys,ive made,pulled off road immediately to cool down
 
In my experience, overheating under load like this is unfortunately a sign of a possible head gasket issues - engine combustion products are forced into the cooling system under load, compromising cooling.
It's a very simple test to check this.

Other possibilities are a blocked radiator core (either internally preventing sufficient coolant flow, or externally preventing sufficient air flow) or a weak/failing water pump. (I don't know what the vectra's pump is like - could the blades be worn/broken off?)
 
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Does the coolant temp reach midway and sit there ? Ie function properly. (Other than fast driving that then raises it)
Can't see it in the info.

Compression test as above could be helpful as I've had a faulty headgasket before with similar symptoms. I've also had a dodgy thermostat with similar symptoms though.
 
Manbatius said:
Does the coolant temp reach midway and sit there ? Ie function properly. (Other than fast driving that then raises it)
Can't see it in the info.

Compression test as above could be helpful as I've had a faulty headgasket before with similar symptoms. I've also had a dodgy thermostat with similar symptoms though.
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Yeah more or less,but will rise if drive long enough,defo believe its the pump,no movement in header tank (water) when accelerator is pressed,dont think its circulating
 
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glenman1966 said:
Yeah more or less,but will rise if drive long enough,defo believe its the pump,no movement in header tank (water) when accelerator is pressed,dont think its circulating
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Yeah just reading above about the propeller shaft being a known issue.

I was just checking about the level getting steady. When I had a stuck open thermostat once it wouldn't get up to temp. But long drives would struggle.

I also wonder if your car has plastic impellers. A lot of manufacturers switched to plastic but... They bring their own issues.

Unfortunately it does sound like you have knew faults and timing belts are not cheap. The flip side is once the belt and pump is done it's one to tick off for some time. (Unless you recently did it !, I assume not as it's best practice to change water pump same time)
 
Manbatius said:
Yeah just reading above about the propeller shaft being a known issue.

I was just checking about the level getting steady. When I had a stuck open thermostat once it wouldn't get up to temp. But long drives would struggle.

I also wonder if your car has plastic impellers. A lot of manufacturers switched to plastic but... They bring their own issues.

Unfortunately it does sound like you have knew faults and timing belts are not cheap. The flip side is once the belt and pump is done it's one to tick off for some time. (Unless you recently did it !, I assume not as it's best practice to change water pump same time)
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both timing belt and pump,were done at around 46,000 miles,now on 106,000 so i imagine due to be done anyway
 
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