over heating at motorway speeds HELP
Discussion
Hi all
my brother has a 106 rallye and we are experiencing over heating issues on motorway driving but it runs as normal in town???
its a bit of a head scratcher but iv read that it may be a thermostat stuck open issue, does this sound likely ?
the system has been flushed to the best of our ability so im hoping there are no blockages in it
any advice would be much appreciated as we have a Trackday on Wednesday and trying to sort it before then
thanks
my brother has a 106 rallye and we are experiencing over heating issues on motorway driving but it runs as normal in town???
its a bit of a head scratcher but iv read that it may be a thermostat stuck open issue, does this sound likely ?
the system has been flushed to the best of our ability so im hoping there are no blockages in it
any advice would be much appreciated as we have a Trackday on Wednesday and trying to sort it before then
thanks
Has it been bled fully? If the S2 is anything like the S1 XSi I had, the coolant reservoir is down by the radiator which isn't the highest point, and you can get airlocks in the system. Mine had a bleed screw (small allen screw) in the thermostat housing which i think was the highest point.
The procedure in the Haynes manual is to use a 'header tank' to reduce air being trapped in the system, which can be achieved by using a 'suitable bottle' with a seal between the bottle and the expansion tank. (Peugeot dealers apparently have a special header tank for this). The system is then filled with the bleed screws open, with each screw being closed in turn as coolant free from bubbles emerges.
Seemed like a huge faff to me (I vaguely recall trying a lemonade bottle and lots of gaffer tape), so I just ran the engine at a fast idle with the top bleed screw open until it stopped bubbling which seemed to work for me.
The procedure in the Haynes manual is to use a 'header tank' to reduce air being trapped in the system, which can be achieved by using a 'suitable bottle' with a seal between the bottle and the expansion tank. (Peugeot dealers apparently have a special header tank for this). The system is then filled with the bleed screws open, with each screw being closed in turn as coolant free from bubbles emerges.
Seemed like a huge faff to me (I vaguely recall trying a lemonade bottle and lots of gaffer tape), so I just ran the engine at a fast idle with the top bleed screw open until it stopped bubbling which seemed to work for me.
If it were me (no expert on this engine) I would be listening to the above about bleeding/air locks, on some engines they cause similar issues.
Doesn't sound like MAJOR problems, or it would be overheating always.
If all else fails you might try filling it to the brim, parking facing up as steep a hill as you can find and running it with the heater on full and on a fast idle with a large bottle in the rad/expansion bottle cap to keep filling the system while it bleeds.
Doesn't sound like MAJOR problems, or it would be overheating always.
If all else fails you might try filling it to the brim, parking facing up as steep a hill as you can find and running it with the heater on full and on a fast idle with a large bottle in the rad/expansion bottle cap to keep filling the system while it bleeds.
Honest to god, do any of you people who try to be helpful actually know the tiniest thing about engines? If the thermostat was stuck closed it would overheat all the time, as it would if it were water pump or head gasket. If the thermostat was stuck open it would never overheat and take ages to get up to temperature, if ever. The main thing that causes over heating at high speed but not low is a knackered radiator. Blocked, fins rotted away, whatever.
I have also known water pump impellers to lose grip on its driving shaft at speed too one on a K series and one on a 2 litre 8 valve Golf 
( I always remember s
t like this) most other loose impellors I have witnessed lose their drive altogether and you have obvious lack of circulation and easy to diagnose 
but apart from this I am with FordPrefect on the other suggestions
( I always remember st like this) most other loose impellors I have witnessed lose their drive altogether and you have obvious lack of circulation and easy to diagnose but apart from this I am with FordPrefect on the other suggestions FordPrefect56 said:
Honest to god, do any of you people who try to be helpful actually know the tiniest thing about engines? If the thermostat was stuck closed it would overheat all the time, as it would if it were water pump or head gasket. If the thermostat was stuck open it would never overheat and take ages to get up to temperature, if ever. The main thing that causes over heating at high speed but not low is a knackered radiator. Blocked, fins rotted away, whatever.
Yep, this.Surely if the overheating is when the engine is working hard but OK when the engine is not working hard then it suggests that the cooling is inadequate for high outputs. That could be because the rad is partially blocked, which seems not to be the case, so is it a circulation problem. I'd have the stat out first to check if it's not opening fully, after that ensure no air locks as these Pug systems are notorious for that, and after that the pump.
LarJammer said:
What are the symptoms when it overheats?
Thanks for the reply.It's no problem at all in traffic or on B roads, but anything over say 50 mph and the temp rises, at motorway speed the warning light comes on. It's never boiled over, there no steam etc. I was thinking it's not a head gasket as that would overheat in traffic as well? Maybe the water pump is just not working well enough to cop with higher loads, lost an few impellers maybe?
Any advice gratefully received
Sardonicus said:
I have also known water pump impellers to lose grip on its driving shaft at speed too one on a K series and one on a 2 litre 8 valve Golf ( I always remember st like this) most other loose impellors I have witnessed lose their drive altogether and you have obvious lack of circulation and easy to diagnose but apart from this I am with FordPrefect on the other suggestions
This. ( I always remember st like this) most other loose impellors I have witnessed lose their drive altogether and you have obvious lack of circulation and easy to diagnose but apart from this I am with FordPrefect on the other suggestions Had the same problem on a few old BMWs and VWs and was caused by said plastic impeller water pumps. As said, over time the plastic moulding seperates (or something) from the shaft. It just about grips onto the shaft enough at low rpms, but at high rpms it can't handle the load and the shaft spins faster than the impeller, if that makes sense?
If the Pug has a plastic pump, it's a good chance that's the cause.
SuperchargedVR6 said:
This.
Had the same problem on a few old BMWs and VWs and was caused by said plastic impeller water pumps. As said, over time the plastic moulding seperates (or something) from the shaft. It just about grips onto the shaft enough at low rpms, but at high rpms it can't handle the load and the shaft spins faster than the impeller, if that makes sense?
If the Pug has a plastic pump, it's a good chance that's the cause.
Most do nowadays in saying that they dont all fail Had the same problem on a few old BMWs and VWs and was caused by said plastic impeller water pumps. As said, over time the plastic moulding seperates (or something) from the shaft. It just about grips onto the shaft enough at low rpms, but at high rpms it can't handle the load and the shaft spins faster than the impeller, if that makes sense?
If the Pug has a plastic pump, it's a good chance that's the cause.
VAG still subsidise the price of their water pumps, probably the plastic impellers many heat cycles over the years and the fact its forced over that knurled finish, although I have also changed a Rover 100 K series water pump (metal impeller) so its not just the plastic/fibre pumps in fact IIRC this was the 1st time I had seen a impeller leave its shaft but it was many years ago and I am not getting any younger 
I had similar with a Nova GTE years ago, the temp gauge seemed to tally up with throttle application, flat out and it shot up, poodling and it was fine. Also at motorway speeds the temp gauge would rise.
Another symptom that it had for a while was a very slight misfire on initial start up in the morning.
It turned out the Head Gasket had failed.
Another symptom that it had for a while was a very slight misfire on initial start up in the morning.
It turned out the Head Gasket had failed.
Edited by eybic on Friday 27th May 16:22
FordPrefect56 said:
Honest to god, do any of you people who try to be helpful actually know the tiniest thing about engines? If the thermostat was stuck closed it would overheat all the time, as it would if it were water pump or head gasket. If the thermostat was stuck open it would never overheat and take ages to get up to temperature, if ever. The main thing that causes over heating at high speed but not low is a knackered radiator. Blocked, fins rotted away, whatever.
Honest to god, if any of you knew.............What say you now then?
As has been said above, you now need to be looking at stat, pump, air locks & any collapsed hoses or pipes partially blocked.
As the engine is running under partial load and running fine when it needs a low level of cooling.
But not so when under a heavy load and needs more cooling there must be something causing restricted cooling water flow.
As the engine is running under partial load and running fine when it needs a low level of cooling.
But not so when under a heavy load and needs more cooling there must be something causing restricted cooling water flow.
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