R75 2.5 auto overheating/cylinder block drain plug

[Spordan]

Hi, had an issue with the car overheating on friday (temp had been running a little hot for around a week - up to 110 in traffic - and I'd topped up the coolant a little at the time).

On Friday it properly overheated and it's been on the drive since.

I have no experience with this, so any advise would be gratefully received!

- The coolant expansion tank is still sitting at max level, and I can't see any leak from a cursory inspection.

My thoughts were either:
I'd overfilled the coolant (as the level is quite difficult to see).
Airlock.
Thermostat stuck.

I've ordered a new thermostat due to come tomorrow, since they were reasonably cheap, but I intended first to drain the coolant and flush water through to check for any blockages - I took a sample of coolant from the expansion tank and seems to have slight traces of rust (or possibly radiator seal or similar).

I've got the car up on axle stands at the moment.
I googled for a guide (since Haynes doesn't seem very clear on this), and i'm meant to release a cylinder block drain plug, to drain the coolant.
I *think* I've found it (although not 100%), but it's in an awful place to reach without a lift - I can't fit a socket wrench in the gap, and I can't get leverage with a spanner to open it because of laying on my back reaching up

Add to that I'm also not certain what i'm trying to reach is indeed the plug! (13mm hex, I think).

So my question is; is it possible to drain the coolant via the bleed screw that's supposed to be on one of the hoses? At least to the point I can flush water through, and then replace the thermostat?

I would take it to a garage, but not having much luck (seems they don't want to touch it )

Many thanks,
Jordan

[Stag>75]

Originally Posted by Spordan

Hi, had an issue with the car overheating on friday (temp had been running a little hot for around a week - up to 110 in traffic - and I'd topped up the coolant a little at the time).

On Friday it properly overheated and it's been on the drive since.

I have no experience with this, so any advise would be gratefully received!

- The coolant expansion tank is still sitting at max level, and I can't see any leak from a cursory inspection.

My thoughts were either:
I'd overfilled the coolant (as the level is quite difficult to see).
Airlock.
Thermostat stuck.

I've ordered a new thermostat due to come tomorrow, since they were reasonably cheap, but I intended first to drain the coolant and flush water through to check for any blockages - I took a sample of coolant from the expansion tank and seems to have slight traces of rust (or possibly radiator seal or similar).

I've got the car up on axle stands at the moment.
I googled for a guide (since Haynes doesn't seem very clear on this), and i'm meant to release a cylinder block drain plug, to drain the coolant.
I *think* I've found it (although not 100%), but it's in an awful place to reach without a lift - I can't fit a socket wrench in the gap, and I can't get leverage with a spanner to open it because of laying on my back reaching up

Add to that I'm also not certain what i'm trying to reach is indeed the plug! (13mm hex, I think).

So my question is; is it possible to drain the coolant via the bleed screw that's supposed to be on one of the hoses? At least to the point I can flush water through, and then replace the thermostat?

I would take it to a garage, but not having much luck (seems they don't want to touch it )

Many thanks,
Jordan

Don't go doing these things until you have a very firm diagnosis. But a few comments before others chime in:

The coolant in the expansion tank should almost be at the bottom of it when the car is cold. The mark is on the side of it, very low down.

The bleed screw is in one of the high hoses so the idea is that air (which rises to the top) should be expelled from there. So to answer your question, it is not the one to drain the system.

The drain bolt you are referred to will only drain the block, not the radiator etc.

Back to the issue of overheating. It may be overheating for various reasons; cooling fan not working, thermostat stuck, blockage somewhere .....

You can search many threads on the V6 overheating, here is one you can start reading and digesting but there are many others:

http://www.the75andztclub.co.uk/foru...d.php?t=216402

And another:

http://www.the75andztclub.co.uk/foru...d.php?t=215294

And if someone has put some sort of radiator sealant into the system then there are threads where that has happened.

I expect someone else will post in with some further comments shortly.

[rrobson]

With the hot weather we've been having recently and the fact that these engines run quite warm a non operational fan could well be the reason the cars overheated. Simple and free to test.
If your loosing a little coolant then you may have an airlock also.
Unlikely to be the thermostat as it would have shown up in the first five mins of driving but as said they aren't too expensive and relatively easy to change.

[Spordan]

Thanks for the advice guys!
I forgot to say I'd checked the fan, and it appears to be working as expected (kicking in different speeds at the correct temps).

The hoses seem to be hot too.

Stag>75, the coolant being at the bottom when cold is a worry; it makes me think I may well have over-filled it, so this will be the first thing I check tonight!
Thanks for the links too, been having a read through of different threads on the forum today and it's giving me a better idea of things.

rrobson, it started to overheat after about 15-20 minutes of driving, so would this make a thermostat issue be less likely? To be honest I had a search on google on the weekend and read thermostat issues were a fairly common issue on these cars, so I figured I'd order one to save having to wait a week if it turned out that was the problem


Plan for tonight then would be to drain off some of the coolant so it's down to the correct level, and give that a go - if I'm having trouble reaching the drain plug, and the bleed screw is on a high hose, can you see any problem with just disconnecting the lower radiator hose and draining as much out as possible from there (short of making a mess)? I have plenty of coolant in the house

Thanks for the help!

[T-Cut]

Running with too much coolant in the expansion tank isn't a cause of overheating. It's the opposite you should worry about. Typical cause is a leak which allows air into the system. You then top up the header tank and you've an air lock. A circulating bubble gives strange effects with the gauge and the lack of coolant causes overheating.

TC

[SD1too]

Originally Posted by Stag>75

Don't go doing these things until you have a very firm diagnosis.

Originally Posted by Spordan

I'd checked the fan, and it appears to be working as expected (kicking in different speeds at the correct temps).

So what were the temperatures Jordan? Was the fan running when the temperature reached 110°? Have you carried out the 'demist test'?

"As expected", "different speeds" and "correct temps" is too vague I'm afraid.

Simon

[Spordan]

Thanks for the replies guys.

I ran it last night with the demister on; fan's slow speed working as expected.
Gave it 15 minutes idling and temp on display settled around 100 or so, put it to 1500-2000 revs and temp went up to about 110 - the higher speed fan kicked in, so seems good on that front.

I loosened the bleed screw during this and a bit of coolant and seemingly a fair amount of air came out (bubbles in the coolant) - this was before temp got up to boiling.

The car's at my parents at the moment, and they are (understandably) a little angsty about me potentially making a mess on the drive, so I'm taking it down to a local garage tomorrow morning, and asking them to flush and (properly) refill it, and then we can assess from there

Thanks for the help!

[StewartIngram]

I've been posting about this and my experience on another thread. Check the smaller bore hose that goes into the expansion tank, just below the filler cap. Take it off, inspect the connector moulding on the tank. You might think this is about 5-6mm diameter - IT ISN'T! Inside there is a tiny 1mm hole, which on mine was blocked. It took me about an hour to clear it(easier with the tank off the car), with a combination of kitchen limescale remover and a makeshift drill made from hard brass wire (model shop). I also ran a 3mm drill through afterward. This bleed hole allows expanded water in the radiator to get back into the tank when hot. All is now well with mine.

Stewart

[tony2]

Didn't have any overheating with my V6 but, I did have strange happenings with the water level and what I thought was a partially blocked Heater Core.
If you suspect someone has used Rad Weld or some other form of sealant in the cooling system, check the Oil Cooler for blockage or restriction.
Here is my saga......Hope it helps you.

http://www.the75andztclub.co.uk/foru...d.php?t=220564

[SD1too]

Originally Posted by Spordan

... I'm taking it down to a local garage tomorrow morning, and asking them to flush and (properly) refill it ...

I wouldn't do that Jordan. Local garages don't understand the K series cooling system and they have a tendancy to jump to the conclusion that a head gasket has gone which, on the V6, is extremely unlikely. With this club's help, together we should be able to get a pretty good idea of what's wrong before you commit yourself to spending big money on labour charges.

Can you run the engine up to 100° again, then carefully feel the bottom radiator hose with your hand. It's the one containing the bleed screw. Is it very hot or cool?

Do you have a 2 speed with resistor fan system or a 3 speed?

I loosened the bleed screw during this and a bit of coolant and seemingly a fair amount of air came out ...

The bleed screw should not be loosened when the engine is running. It is for use during refilling from dry only, with the engine switched off.

You can drain and refill the cooling system yourself. You don't need to pay a garage. Here is the recommended MGR procedure.

Most importantly, do not let anyone put K-seal, Steel Seal or any other magic gunge into your cooling system.

Simon