Discussion
Wotcha
I was wondering if anyone else has had the expierience of having the header tank regulary chuck water out when the engine's hot? I first thought that the thermostat was playing up (see Stat mucher topic) but I now suspect a cracked block/ head/ duff head gasket as you can fill the water system, bleed it and get it good and hot on the drive just ticking over and its fine. Take it out for a drive though and when you stop the header tank has overflowed, lost its coolant and the temp gauge starts to show temperature 'spikes' of suddenly increasing from 80 to 95°C. I've checked the compressions and all cylinders seem decent (13.4 to 15.0 bar ) also just to add to my confusion the water system retains pressure overnight and the oil level in the sump doesn't appear to be increasing. Oh and I've tried a bottle of radseal and replaced all of the water hoses as well as the thermostat.
Any ideas anyone before I whip the heads off?
Matt
I was wondering if anyone else has had the expierience of having the header tank regulary chuck water out when the engine's hot? I first thought that the thermostat was playing up (see Stat mucher topic) but I now suspect a cracked block/ head/ duff head gasket as you can fill the water system, bleed it and get it good and hot on the drive just ticking over and its fine. Take it out for a drive though and when you stop the header tank has overflowed, lost its coolant and the temp gauge starts to show temperature 'spikes' of suddenly increasing from 80 to 95°C. I've checked the compressions and all cylinders seem decent (13.4 to 15.0 bar ) also just to add to my confusion the water system retains pressure overnight and the oil level in the sump doesn't appear to be increasing. Oh and I've tried a bottle of radseal and replaced all of the water hoses as well as the thermostat.
Any ideas anyone before I whip the heads off?
Matt
Relax Matt!
My 400 does/used to do this. In the end I reckoned it was cos I was over filling it. The spikes are the pressure cap blowing off, and that for some reason plays havoc with the temp. (maybe its a pressure/boiling point thing)
Once I got out of the habit of overfilling and after I had bled it, it was fine. To be on the safe side check the pressure cap is the right one (they have different blow off springs) and make sure you have no leaks or air ingression points in the rest of the system (the swan neck filler point is quite often a leak/ingression point as it sometimes fouls the underside of the bonnet and gets moved on its seal.
I now don't check the water level except when its cold and then its never more than half way up the reservoir. ny more than that and it will blow its cap!
Have a relaxed Xmass Matt, and leave the heads on!
Andy 400se
My 400 does/used to do this. In the end I reckoned it was cos I was over filling it. The spikes are the pressure cap blowing off, and that for some reason plays havoc with the temp. (maybe its a pressure/boiling point thing)
Once I got out of the habit of overfilling and after I had bled it, it was fine. To be on the safe side check the pressure cap is the right one (they have different blow off springs) and make sure you have no leaks or air ingression points in the rest of the system (the swan neck filler point is quite often a leak/ingression point as it sometimes fouls the underside of the bonnet and gets moved on its seal.
I now don't check the water level except when its cold and then its never more than half way up the reservoir. ny more than that and it will blow its cap!
Have a relaxed Xmass Matt, and leave the heads on!
Andy 400se
Unfortunatly, the symptoms you describe were only cured with head gasket replacement in my 390. Many months of replacing various parts of the system changed absolutely nothing.
It didn't matter what the coolant level was, it didn't matter if you were hammering the car, or just going for a gentle drive, it didn't matter if it was a hot or cold day, the needle would always go into the red, go up and down a number of times, then dump the coolant.
It didn't matter what the coolant level was, it didn't matter if you were hammering the car, or just going for a gentle drive, it didn't matter if it was a hot or cold day, the needle would always go into the red, go up and down a number of times, then dump the coolant.
But surely if it was a head gasket you would see water in the oil, or steam from the oil filler, or even oil in the water, or loadsa water coming out the exhaust? (Then the engine wouldn't run properly anyway) If he has none of this, and there is no obvious external leak around the head area it cannot be the head gasket can it? If the plugs stay dry there cannot be a leak there.
It has to be the thermostat/airleak/airlock/overfill scenario doesn't it, or have I just had far too much Xmass spirit?!?
Andy 400se
It has to be the thermostat/airleak/airlock/overfill scenario doesn't it, or have I just had far too much Xmass spirit?!?
Andy 400se
I know what you're saying Andy, but it depends on where the gasket may have failed.
My mates Espace had no oil in water/water in oil and the gasket had failed between a cylinder and a waterway. It was watertight enough not to let the oil into the cylinder, but not tight enough to keep the air from the compression of the piston blowing the water up. We sort of knew this before taking the head off as you could smell the diesel (yuk - spit) in the header tank
But I'd say your suggestion about the pressure cap is proberly the first thing to try.
Keep up the Christmas spirit
I am! 
Cheers,
Dave.
Edited by Dave_H on Wednesday 26th December 20:14
My mates Espace had no oil in water/water in oil and the gasket had failed between a cylinder and a waterway. It was watertight enough not to let the oil into the cylinder, but not tight enough to keep the air from the compression of the piston blowing the water up. We sort of knew this before taking the head off as you could smell the diesel (yuk - spit) in the header tank
But I'd say your suggestion about the pressure cap is proberly the first thing to try.
Keep up the Christmas spirit
I am! Cheers,
Dave.
Edited by Dave_H on Wednesday 26th December 20:14
Mine used to do that - you need to bleed the rad... it costs nothing... turn on interior fan ... leave rad cap off .. top up water to correct level .. start engine and squeeze rubber 'real hard' (20 to 30 times !) pipes near rad to get some water surge to dislodge any rogue air.
It's this trapped air which expands when hot which pushes out the water from the header.
You could also blead the heater matrix - (engine cold) - take off the top heater pipe at the rear top of the engine, get a friend to bloke with thumb the inlet manifold side of the water system, hold pipe verticle and blow ward into the water pipe top up (this aint easy or graceful). Re-attach pipe !
You can also check the system for leaks - particularly
the rad - if there are telltale green streaks down the sides it needs replacement. This could leak enough air to cause all your problems.
Only after all the above would I then suspect the head gasket .. Did you know that good garages have testing enqipement like water chemical analysis (to check for combustion gases) and Exhaust gas analysers can also be used to check for head leaks. Why not use a good garages services to track down the problem - then do the expensive work your self.
Hope the above helps.
It's this trapped air which expands when hot which pushes out the water from the header.
You could also blead the heater matrix - (engine cold) - take off the top heater pipe at the rear top of the engine, get a friend to bloke with thumb the inlet manifold side of the water system, hold pipe verticle and blow ward into the water pipe top up (this aint easy or graceful). Re-attach pipe !
You can also check the system for leaks - particularly
the rad - if there are telltale green streaks down the sides it needs replacement. This could leak enough air to cause all your problems.
Only after all the above would I then suspect the head gasket .. Did you know that good garages have testing enqipement like water chemical analysis (to check for combustion gases) and Exhaust gas analysers can also be used to check for head leaks. Why not use a good garages services to track down the problem - then do the expensive work your self.
Hope the above helps.
There will always be a great amount of debate about this, so the only sure way is to get it checked properly.
In the case of my 390, there was no oil in the water, no water in the oil, no steam from the oil filler, and the engine ran fine. I tried the variety of bleeding methods numerous times, and I also changed the expansion tank cap, the thermostat and made the cap on the swan neck pipe seal a little bit better, oh, and replaced a load of the pipes which were looking a touch 'fragile'.
The only thing that made any difference was the head gaskets.
In the case of my 390, there was no oil in the water, no water in the oil, no steam from the oil filler, and the engine ran fine. I tried the variety of bleeding methods numerous times, and I also changed the expansion tank cap, the thermostat and made the cap on the swan neck pipe seal a little bit better, oh, and replaced a load of the pipes which were looking a touch 'fragile'.
The only thing that made any difference was the head gaskets.
At the end of the day, if it is the Head Gasket that needs replacing it is an absolute doddle to do. Remember that the trusty old Rover block was designed in the late 50's and is not at all complex.Its only 8 overhead valves per head with pushrods from the Cam. You can remove it with the most basic socket set. I've stripped numerous Rover Blocks in the Past and you can do anything with a set of imperial sockets! So i'd stop talking about it and whip the head off to have a look, because it wont take long at all!
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