Overheating/airlock problem HELP!!!!!

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S

spurs

Active Member
Posts
249
Location
potters bar, herts
Hi all,

I'm in need of some help please.....I have noticed that my systems has been pressurising as posted before, but while driving home today the 300tdi disco decided to over heat as the temperature gauge rose I pulled over and turned her of.
On inspection under the bonnet the system had pressurised and was blowing water out of the header tank, once all had settled I undid the cap and took the radiator bleed cap screw of. What I saw was that the water was only half way up the radiator even tho I had just refilled the system with more water.

What do you guys think the problem is could it be p gasket?

Kyle
 
you need to check system for leaks,p gasket if leaking is visible behind alternator running down the block ,check rad is in good condition and gets hot all over after its up to temp ,ensure that cooling system is full by it overflowing with thermostat housing plug removed (which is something you should do regularly to check system as expansion bottle level isnt necessarily the same as engine)head gasket would be my first thought whilst checking the rest
 
it would cause coolant loss which will lead to poorer cooling and pressurisation if level gets too low , tdis dont really suffer from airlocks as some engines which are hard to shift , as long as you over fill will thermostat housing bung off system is full
 
Update: today I have spent most of the day on the Landy, firstly I changed the p gasket as it was leaking and put a new water pump on and all went well with that. When it came to bleeding the system well that was a fun job......I had the rad filler of as well as thermostat filler and expantion tank cap of as well so filled system through thermostat and let bubbles run out, then I would get a whole load of water gush out. I finally thought I had solved the problem so went for a drive then I noticed that the heater would be cold then all of a sudden get hot and the temp gauge would drop slightly to a position I would expect it to be for that drive. I then stopped popped in shop came out and same thing with heater cold then hot. Has anyone got any ideas, could it be a slight pin prick somewhere cause air lock?

Kyle
 
Ok, so today I took Landy out and all seemed really heater working when expected and engine warming up about normal time. After driving for a little while I then stopped and got out for 5 mins and got back in and all was good heater wise then went to get some dinner and stopped for fifteen minutes, but when I re started the heater went cold again then kicked back and temp gauge dropped a bit.......what is this problem.....the system hadn't pressurised when I got back. Any ideas?

Kyle
 
Hi

Sounds like it could be a possible air lock in the heater system to me . I had someting similar once. I now always have the front end of car higher than the back when I top it up and squeeze the top hose as I do it. The heater controls are also in the hot position.

Put a new good quality/genuine thermostat in it

However as the car has overheated a few times and only you know how much it could be worth while taking it to a garage for a Sniff Test and a Cooling system pressure test.

This will check for exhaust gasses in the cooling system and for any leaks, as it is possible you have a Head gasket failure or a warped head as well. This could be the cause of over pressurised system

If coolant can leak out it can suck air in when cooling.

A common problem with overheating that most people forget about is the oil cooler thermostat, if this is not working or very slow or has a delayed action it will cause the coolant to overheat also.

Is the viscous fan working OK?

The best course of action when overheating is not to switch the engine off, but to immediately put the heater on full (max temp and fan speed) and pull over. This keeps the oil and water circulating , hence cools the engine quicker. If you switch off the heat stays in the engine block for a long time and can distort the cylinder head if not already done so.

Regards

Jonathan
 
Last edited:
years ago i similar stuff going on ,my heater would keep going off ,i was loosing coolant , went through god knows how many ways to clear air locks but it was head gasket failing, pushes out coolant then as engine cools down sucks in air . a discos heater will go cold as soon as coolant is on bottom of expansion tank. dont buy cheap gasket , i did and only got 1500 miles out of it ! get proper landy one its only about £2 more. if you have ran with water below bottom of tank the head is higher and staved of coolant
 
Many thanks for all the info guys it's much appreciated. A little update for today. I have been out in the Landy today and temperature all seems good and heater was working fine. When I got home there was no pressure in the header tank and it wasn't bubbling.....what I did notice was abit of steam/vapour coming out of header......does this sound normal?

Kyle
 
I thought pressure in the header tank was normal, after all, it has a pressure relief cap fitted to it? If there is no pressure it may mean there is a leak somewhere maybe?
 
Hi

Yes you are correct KiwiTDI. If I remember correctly the working pressure when hot is 15psi.

If there is no pressure at all when checking after immediately stopping driving at normal temp there is a problem.

New caps are available for only a few pounds, and are one of those parts that are cheap to change that people forget about. Most people concentrate on the usual issues caused by Radiators water pumps,thermostats and leaks and forget about other minor but important parts of the cooling system.

Obviously as you state correctly another leak is also/probably somewhere in the system. Splits in the Header tank seams and leaks from the hoses, gaskets etc are possible, and not unusual.

The pressure increases the boiling point of the coolant, that way the coolant does not boil under normal operating conditions.
So you always have to be very careful when removing the cap when hot as the sudden depressurisation will cause the coolant to boil, and splurt everywhere!!!

Regards

Jonathan
 
UPDATE......
Ok everyone took the old girl to the garage today to check for a weak headgasket and yes the head gasket is failing as bubbles are coming up into the coolant apparently.

So the next question is, I believe I have a standard headgasket in as I can't see any holes along the headgasket when it's in place. So what is the best head gasket to get can any one recommend one?

Also with regards to the one two and three hole gaskets do they leave the factory with this style gasket?

Kyle
 
If it has no holes, it is the thickest one that is available. has it been replaced by a previous owner ??

Buy Genuine, I think they are made by Elring but I can not remember at the moment

Regards

Jonathan
 
Jonathan,

It had supposedly been changed two years ago but who knows. Garage has said to me that it may well have a cracked head.......we will see. Keep you all posted.
 
Hi

It is possible the Head is cracked or warped

If required the Head can be individually pressure tested and if OK it can then be skimmed if there is enough metal left on it. Or it could be a case of a new Head ????

Only a strip down and further work will tell.

You have to be very careful as you are already using the thickest gasket. Do you know what size the original one was ?

Regards

Jonathan
 
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