Possible Coolant Problemi

[Angel123]

I was checking oil, coolant, etc the other day when I noticed the header tank was nearly empty. I refilled it. I have done 2 or 3 140 to 200 mile journeys recently since 1st spotting header tank was low. Checked it again yesterday and it had gone down again. That was after another 130 mile journey. The car is running perfectly. Nothing is showing untoward. The temp gauge sits where it always, about a third of the way up. No leaks underneath or in engine bay that I can see. If anyone has any ideas what this problem might be, any advice, I would be very grateful. Thanks.

[ambermarine]

I was checking oil, coolant, etc the other day when I noticed the header tank was nearly empty. I refilled it. I have done 2 or 3 140 to 200 mile journeys recently since 1st spotting header tank was low. Checked it again yesterday and it had gone down again. That was after another 130 mile journey. The car is running perfectly. Nothing is showing untoward. The temp gauge sits where it always, about a third of the way up. No leaks underneath or in engine bay that I can see. If anyone has any ideas what this problem might be, any advice, I would be very grateful. Thanks.

Have you had any work done on the engine in recent times which required the coolant to be drained.After the engine is refilled with coolant this situation can occur if the correct procedure for refilling the engine is not followed the short answer to that is that an air lock forms within the system and stays there until it eventually clears this can take sometime. The other cause can be a leaking cap or a leaking seal on the level sensor both on the expansion tank which allows the coolant to evaporate and be forced out by the pressure difference ,this at full running temprature will dissapear as a vapour. Ease back the rubber cover on the level sensor on your expansion tank and look for tell tale coolant if it is wet replace the O ring by unscrewing the sensor from the tank ,dissconect the sensor from its electric supply first .If it is dry than it could be the cap on the tank ,just get a new one is the quickest way to check that.

[Angel123]

There was a radiator fitted about 3 years before my time according to the service history. I will check the cap and level sensor. But should I wait till stone cold. Thanks for your help. Will keep you posted.

[ambermarine]

There was a radiator fitted about 3 years before my time according to the service history. I will check the cap and level sensor. But should I wait till stone cold. Thanks for your help. Will keep you posted.

Never take the cap off the expansion tank unless it is stone cold.There is another possibility in that the water pump is failing ,if it is not working it will not circulate the water round the engine and radiator, the circulation will only occur on a thermal basis but boils as well, this causes the coolant to evaporate and leave through the pressure release valve on the expansion cap.

You can do a visual check on the water pump operation by revving the engine from cold the coolant will be seen rushing up into the expansion tank it is more pronounced because the thermostat does not allow the coolant to enter the radiator from the engine until it as warmed up, the bypass leads off to the expansion tank then back to the engine.

[Angel123]

If the coolant rushes up into the expansion tank does this mean the water pump is failing. I would have thought it would have over heated if water pump had failed. Sorry if a bit slow on fallowing your leads.

[brendangeorge]

If the coolant rushes up into the expansion tank does this mean the water pump is failing. I would have thought it would have over heated if water pump had failed. Sorry if a bit slow on fallowing your leads.

I have a similar problem on my LS430 - the resovoir drops low (1/2" off the bottom) and stays there - no drips or leaks (I put paper under it over night). The car runs up to temp and is rock steady and the engine runs like a dream (after 200K miles). I had to fit a new rad at the 200K belt change and noticed the problem then. I talked to a very experienced Lexus mechanic and he said it is fine a lot of these cars do this even 400s. I keep my eye on the temp gauge and check the reserve tank and it is always at the same level and the temp is rock steady. I have plagued the guys who did the rad work etc and wanted to kill them for not changing a 200K miles old water pump (even though it is not a problem) but they can find no leaks. I am going to look at what ambermarine suggests (thanks) but suspect that old Wally is right and the car is fine. I also changed the cap as a precaution.

I just started up from cold and some water is pushed into the reserve tank (but not) much so I assume the water pump is working. I am confused because the water level drops to the low level and stays constant after I fill it up - if there was a leak then I should loose cooland and the engine overheat.

I am going to look at the sensor as ambermarine suggests.

I have had this little challenge for 3 months :)

[ambermarine]

If the coolant rushes up into the expansion tank does this mean the water pump is failing. I would have thought it would have over heated if water pump had failed. Sorry if a bit slow on fallowing your leads.

It means the pump is working and yes the car can overheat depending on what kind of driving you are doing if you are toddling round town in traffic it will probably overheat but not if you are driving down the motorway or trunk road at 60 mph as the force of cold air around the engine and the thermal flow through the radiator will keep it at its normal temprature .There is no need to panic just follow the logical steps of identifying the cause of your problem

[ambermarine]

If the coolant rushes up into the expansion tank does this mean the water pump is failing. I would have thought it would have over heated if water pump had failed. Sorry if a bit slow on fallowing your leads.

I have a similar problem on my LS430 - the resovoir drops low (1/2" off the bottom) and stays there - no drips or leaks (I put paper under it over night). The car runs up to temp and is rock steady and the engine runs like a dream (after 200K miles). I had to fit a new rad at the 200K belt change and noticed the problem then. I talked to a very experienced Lexus mechanic and he said it is fine a lot of these cars do this even 400s. I keep my eye on the temp gauge and check the reserve tank and it is always at the same level and the temp is rock steady. I have plagued the guys who did the rad work etc and wanted to kill them for not changing a 200K miles old water pump (even though it is not a problem) but they can find no leaks. I am going to look at what ambermarine suggests (thanks) but suspect that old Wally is right and the car is fine. I also changed the cap as a precaution.

I just started up from cold and some water is pushed into the reserve tank (but not) much so I assume the water pump is working. I am confused because the water level drops to the low level and stays constant after I fill it up - if there was a leak then I should loose cooland and the engine overheat.

I am going to look at the sensor as ambermarine suggests.

I have had this little challenge for 3 months :)

Keep filling it up the system contains 11 litres of coolant and if you have an air lock that could account for 3 or 4 litres

the expansion tank only holds about 2.5 litres.

[Angel123]

I have waited till this morning to carry out checks so the engine is stone cold. Coolant pushed up into the expansion tank, not a mad rush, but pushed through all the same. Last Saturday I did a 60 mile trip up the M6. Then got caught in heavy traffic in Preston for about 30 mins. Then another 60 miles back. Everything was fine. I am going to change the cap from the expansion tank, even thou it looks fine. As for the level sensor, I can't seem to move it. Its just a pipe going to the side of the expansion tank I will then take the car for a run to see if anything changes with new cap. Will update later.

[brendangeorge]

If the coolant rushes up into the expansion tank does this mean the water pump is failing. I would have thought it would have over heated if water pump had failed. Sorry if a bit slow on fallowing your leads.

I have a similar problem on my LS430 - the resovoir drops low (1/2" off the bottom) and stays there - no drips or leaks (I put paper under it over night). The car runs up to temp and is rock steady and the engine runs like a dream (after 200K miles). I had to fit a new rad at the 200K belt change and noticed the problem then. I talked to a very experienced Lexus mechanic and he said it is fine a lot of these cars do this even 400s. I keep my eye on the temp gauge and check the reserve tank and it is always at the same level and the temp is rock steady. I have plagued the guys who did the rad work etc and wanted to kill them for not changing a 200K miles old water pump (even though it is not a problem) but they can find no leaks. I am going to look at what ambermarine suggests (thanks) but suspect that old Wally is right and the car is fine. I also changed the cap as a precaution.

I just started up from cold and some water is pushed into the reserve tank (but not) much so I assume the water pump is working. I am confused because the water level drops to the low level and stays constant after I fill it up - if there was a leak then I should loose cooland and the engine overheat.

I am going to look at the sensor as ambermarine suggests.

I have had this little challenge for 3 months :)

Keep filling it up the system olds 11 litres of coolant and if you did have an air lock that could account for 3 or 4 litres

the expansion tank only holds about 2.5 litres.

Thanks - when the cooling system was refilled the garage assured me they followed the correct proceedure - although I had to put a litre of oil in after the oil change so they did not get that right (don't worry no leaks). I have put at least 5 litres of water and anti-freeze in the expansion tank and the coolant level drops back to the low and contant level - I am going to see if I can check the level sensor seal as you advised. What baffels me is if there is a leak it should keep kicking out water and the engine would overheat. I do all kinds of motoring and have not seen an overheating problem on short, long or motorway blasts.

Many thanks for your suggestions.

Brendan

[Angel123]

I bought the new cap. Then went on a 80 mile run. With a mixture of slow moving traffic and motorway traffic. Same as before, everything perfect. Checked the coolant level about 10 mins after journeys end, it was about a quarter full. Still no leaks I can find. So could be a blockage of some kind. Thanks for all the info given

Tom

[Malc]

I had this similar issue for years with my Mk2. Never caused a days problem and I just accepted that the level went down and occasionally I topped it up. I think it was simply an uneven refill at some stage and was just working it's way through !

Malc

[Angel123]

Update. It appears I have got the cap thing wrong as stated earlier when I thought coolant was still going down after fitting new cap. There was simply not enough coolant in there. So all is fine now. I would like once again to thank everyone for all their help and info which is priceless.

Tom