over heating at motorway speeds HELP
Discussion
Itsallicanafford said:
thanks for the responses chaps.
Could i ask a quick technical question. When hot (or very hot as i was looking after a run with rad. fan on) should the coolant be flowing through the radiator? I pretty sure the answer should be yes but if you look into the expansion tank the water is totally static? Would you not see any movement in this coolant in the tank, being the design of this is directly linked to the rad rather than a pipe fed header tank design.
I'd have thought you should see some movement, I have always seen movement on the cars I've owned whilst the fan is running.Could i ask a quick technical question. When hot (or very hot as i was looking after a run with rad. fan on) should the coolant be flowing through the radiator? I pretty sure the answer should be yes but if you look into the expansion tank the water is totally static? Would you not see any movement in this coolant in the tank, being the design of this is directly linked to the rad rather than a pipe fed header tank design.
You won't see water flowing or swirling round in the expansion tank, it's a fixed tank, just a head of coolant which will expand and contract as the engine heats and cools so you might see the level rise and then lower as the temperature of the water goes up and down but I've never seen it move or swirl unless the system is being refilled from empty.
On my pugs whilst struggling with this problem didn't see massive flow, maybe a little disturbance iirc.
The issue with filling these systems and getting all the air out made me take a radiator cap and modify it so that it had a tube poking out of the top. I'd use this cap for stopping up and bleeding the system, fix a hose to the top of the tube up to a cut down pop bottle slung off the open bonnet to act as a real high up header tank. Then go through the topping up procedure, opening up all the bleed valves on the engine and heater circuits to ensure got all the air out.
Once bled properly, close everything up, clamp off the header tank pipe, take off the modified cap and replace the standard cap.
Unfortunately this, as said was after the second engine screwed up. Never had any issues after, nor on TU Citroens which aren't too different at times.
Have great sympathy with the views expressed by FordPrefect here, we were led up a blind alley at first. As soon as you said chucking coolant out a page or so back this was only ever going one way. Agree with his suggestions on where to go next, or skim head, clean up block properly, etc. Hope that fixes it, and seriously sort out a decent method to fill and bleed the coolant circuit, using every bleed valve.
The issue with filling these systems and getting all the air out made me take a radiator cap and modify it so that it had a tube poking out of the top. I'd use this cap for stopping up and bleeding the system, fix a hose to the top of the tube up to a cut down pop bottle slung off the open bonnet to act as a real high up header tank. Then go through the topping up procedure, opening up all the bleed valves on the engine and heater circuits to ensure got all the air out.
Once bled properly, close everything up, clamp off the header tank pipe, take off the modified cap and replace the standard cap.
Unfortunately this, as said was after the second engine screwed up. Never had any issues after, nor on TU Citroens which aren't too different at times.
Have great sympathy with the views expressed by FordPrefect here, we were led up a blind alley at first. As soon as you said chucking coolant out a page or so back this was only ever going one way. Agree with his suggestions on where to go next, or skim head, clean up block properly, etc. Hope that fixes it, and seriously sort out a decent method to fill and bleed the coolant circuit, using every bleed valve.
Itsallicanafford said:
Thanks Dave for the response, very much appreciated. My apologies in advance if i use the incorrect terminology below, as you can tell i am a layman when it comes to the internal working of engines!
The mechanic did say that they thought the head gasket wasn't particularly tight when they removed it, could coolant have been passing into each of the cylinders and causing the cleaner areas on the pistons?
You mean like wot I just said above?The mechanic did say that they thought the head gasket wasn't particularly tight when they removed it, could coolant have been passing into each of the cylinders and causing the cleaner areas on the pistons?
Itsallicanafford said:
The head is going away to be checked and pressure tested so i assume that they will skim it if required.
Many Thanks
Hmmm. I wouldn't go assuming too much from people who said it wasn't the head gasket but were going to remove the head anyway to check something in the block which it couldn't possibly be and that they couldn't have seen anyway even with the head off. Those of you who know this is actually Pumaracing posting will be well aware of my long held and oft repeated views on the IQ of the average garage mechanic which varies from somewhere between South American Tree Frog on a bad day rising to possibly Ring Tailed Lemur on an exceptionally good one. Many Thanks
My remaining fear is that even with the head skimmed and properly refitted with a new gasket you still won't have cured the original problem if that was filling technique or a coolant hose issue which caused the head to overheat and warp in the first place.
Ok, update...
So, the head is back, it was found to be pretty straight but it has had a very light skim.
The car is at a pug/ citroen specialist, they are currently working on 4 DS's an SM as well as C6's. Talking to the mechanics, they found that when they were starting the engine, the head was getting very hot very quickly. When they turned the engine off they could hear the coolant bubbling in the block but nothing was overflowing out of the rad. This is why they beloved that something was stopping the coolant circulating into the head. You can see from the head gasket there was a small blockage but nothing too serious. The theory then was the head gasket was incorrect, but a new one has been purchased and this looks very similar. The idea is to refit the head and re-test. After that, if the problem is still there, they have suggested opening up some of the coolant holes in the head gasket? I'm not too sure if this is a good idea?
The head had been skimmed before, if too much has been removed, would this alter the compression ratio and could this lead to additional heat being generated in the head?
Again, any comments gladly received.
So, the head is back, it was found to be pretty straight but it has had a very light skim.
The car is at a pug/ citroen specialist, they are currently working on 4 DS's an SM as well as C6's. Talking to the mechanics, they found that when they were starting the engine, the head was getting very hot very quickly. When they turned the engine off they could hear the coolant bubbling in the block but nothing was overflowing out of the rad. This is why they beloved that something was stopping the coolant circulating into the head. You can see from the head gasket there was a small blockage but nothing too serious. The theory then was the head gasket was incorrect, but a new one has been purchased and this looks very similar. The idea is to refit the head and re-test. After that, if the problem is still there, they have suggested opening up some of the coolant holes in the head gasket? I'm not too sure if this is a good idea?
The head had been skimmed before, if too much has been removed, would this alter the compression ratio and could this lead to additional heat being generated in the head?
Again, any comments gladly received.
Do not let them modify the gasket. This is just a bodge to try to cover up a separate fault, one that almost certainly won't work and is likely to cause other problems.
A small increase in compression ratio won't cause overheating, but if the head has had a significant amount of material removed it could raise the CR enough to cause detonation with the engine loaded, and that can cause overheating (as well as more physical engine damage).
Quite honestly the symptoms sound exactly like a big airlock in the cooling system, and these engines are absolutely notorious for being difficult to bleed.
A small increase in compression ratio won't cause overheating, but if the head has had a significant amount of material removed it could raise the CR enough to cause detonation with the engine loaded, and that can cause overheating (as well as more physical engine damage).
Quite honestly the symptoms sound exactly like a big airlock in the cooling system, and these engines are absolutely notorious for being difficult to bleed.
Obviously the amount skimmed off the head will raise compression ratio. Diddn't thicker head gasket used to be one way of dealing with this.
As the garage are supposedly PSA specialists they should know all the dodges about filling and bleeding the cooling system, including the extra high up temporary header tank and using all 3 (iirc) bleed nipples. Best to make sure they do though imo.
As the garage are supposedly PSA specialists they should know all the dodges about filling and bleeding the cooling system, including the extra high up temporary header tank and using all 3 (iirc) bleed nipples. Best to make sure they do though imo.
Chaps, thanks for the reply. I've called them and told them not to touch the gasket, I didn't like the sound of that either. However, they have had another look in the cooling system and although the water pump was new, the fins from the last one were still in the system and causing a blockage.
Bit frustrating as I suppose the head didn't need to come off then, could have saved a few quid if so.
But I suppose the car is new to me and had limited history so I now know that the water pump, cambelt, head gasket are all new (as well as the rad, thermostat, O2 sensor!) Plus, the smoking on acceleration should be sorted by the new valve stems.
Going back together on Monday so fingers crossed...will let you know!
Thanks again for the continuing advice, much appreciated.
Bit frustrating as I suppose the head didn't need to come off then, could have saved a few quid if so.
But I suppose the car is new to me and had limited history so I now know that the water pump, cambelt, head gasket are all new (as well as the rad, thermostat, O2 sensor!) Plus, the smoking on acceleration should be sorted by the new valve stems.
Going back together on Monday so fingers crossed...will let you know!
Thanks again for the continuing advice, much appreciated.
hi all i was wishing for some help i have a 306 tu engine 1.4 it had a leek in the rad on the m40 i got it home ok it over heated so i stop the car and fill it up again so i put a new radiator in it ever since that it. will all ways over heat so i look it some where and thay checked it and thay said yep it the head gasket so i got all the pats new head gasket set new water pump and timing belt and 3 new thermostat new antifreeze got the head skim put it all back toghter on it doing the same thing as before just over heating more on going up hill so i re bleed it with the coke bottle trick but the same so i took the thermostat out and it run fine not i dont get any hot air in the cap when on a long run ony get hot air when it ticking over so i put a nother thermostat in thinking it will be ok now but it still the same ive had ppl looking at it thay dont know what it cued be so plz can some one help
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