P38 4.0L V8 loosing coolant but cannot see where!

Hi,

I have looked over previous threads and cannot find an answer that matches so hoping you guys can help.

I appear to be losing coolant about 1/2 litre every 40 miles

Just had HG done and heads skimmed so hoping it’s not that (paranoid about coolant level hence the checking every 40 miles).
Changed the cap, this brought the problem down from 2litres every 40
After a 20mile run back from work I noticed the cap was hissing slightly (new one), is this normal for it to be venting pressure?
Pipe work is not over pressurised hence hoping its not HG again
Checked under the dash no signs of leakage from the heater matrix O-rings

No signs of leakage from the weep hole in the pump
No signs of leaks on any of the pipe work, stat or radiator.
Overflow pipe from rad to tank flowing OK

The only place I can see coolant is under the tank and around the inside of the wheel arch, but cannot be certain this is overflowing or my shaky hands filling up in the cold outside!


I have tired clearing any crud from around the cap and it seems to seat properly.


Could it be something as simple as needing a new expansion tank? Could the seals be bust after the repeated over heats as the HG was finally letting go




any help/comments welcome

expansion tank can develop fine crack, new cap can leak, wrap in tissue to source leak

oh dear..why you get heads done??

i asking cos i thonks you might be in da ****e..

zen said:

oh dear..why you get heads done??

i asking cos i thonks you might be in da ****e..

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Heads were done as HG had blown, garage pressure tested the block to check for slipped liners before proceeding with skimming and refitting

I'm not sure if yours is like mine, but my 2000 4.6 lost coolant slowly from the area around where two small pipes attach under the throttle body. I ended up replacing the metal plate and seal under there - along with both pipes in the end to get a decent joint.

I used to park with a clean piece of cardboard under the car (in the garage) to see where any drips might be landing under the car. Not definitive, but occasionally helpful.

Turtled said:

I'm not sure if yours is like mine, but my 2000 4.6 lost coolant slowly from the area around where two small pipes attach under the throttle body. I ended up replacing the metal plate and seal under there - along with both pipes in the end to get a decent joint.

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Would I be able to see evidence of the leak without taking anthing apart? any clue as which direction to look from, front, left or right side?

gibby_wls said:

Heads were done as HG had blown, garage pressure tested the block to check for slipped liners before proceeding with skimming and refitting

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some times cracked bores only show up when engines warm

pretty sure it will be a slipped liner on a 4.6 it's a pretty common fault, generally you will need to do a liner mod to cure it

its a 4.0 and the block was pressure tested so hoping not

gibby_wls said:

its a 4.0 and the block was pressure tested so hoping not

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see post 7 all blocks 3.9 on are prone

gibby_wls said:

Heads were done as HG had blown, garage pressure tested the block to check for slipped liners before proceeding with skimming and refitting

Click to expand...

curious to know how that was done with dodgy head gasket on it??

if you thnks it is a water leak put dye in coolent, ie UV and at night after its leaked abit shine uv lamp in engine bay...u will see it then.except i suspect you wont, but truely hope you do!

gibby_wls said:

its a 4.0 and the block was pressure tested so hoping not

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sorry my mistake I got confused! the 4.0 is the same block, I'm not really sure how the block can be properly pressure tested with a knackered head gasket or without the head on at all without a lot of very expensive specialist equipment which your average garage would not have :/

kev1nlm said:

sorry my mistake I got confused! the 4.0 is the same block, I'm not really sure how the block can be properly pressure tested with a knackered head gasket or without the head on at all without a lot of very expensive specialist equipment which your average garage would not have :/

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By blocking up the water ways....observe

Land Rover V8 Cylinder Leak / Crack - YouTube

gibby_wls said:

Would I be able to see evidence of the leak without taking anthing apart? any clue as which direction to look from, front, left or right side?

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I've just noticed that yours is a GEMS, mine is a THOR, so I'm pretty certain yours won't have the same throttle body coolant arrangement. I'm prepared to be corrected though.

I also have so say - having been through what I've been through - that your symptoms do point towards porous block - but it is worth eliminating leaks etc first.

If you do have leaks around the place, they can be easily caused by higher pressures when hot, and can also be hard to find if the water if falling onto a warm surface and evaporating. If you have a good proportion of coolant in (you do have coolant in??) it can be easier to spot because of the residue.

If you don't have coolant, add it. It substantially increases the boiling point of the water, leading to lower pressures. Use the pink stuff - OAT.

Get the system pressure tested it goes on your explanation tank it's pumped with air via makers instructions to pressure . And any leaks will be found porous or not .
Its a simple test and only takes no more than an hour at most the kit is expensive so get a decent garage to do it for you simples .

Saint.V8 said:

By blocking up the water ways....observe

Land Rover V8 Cylinder Leak / Crack - YouTube

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cool

Turtled said:

I'm not sure if yours is like mine, but my 2000 4.6 lost coolant slowly from the area around where two small pipes attach under the throttle body. I ended up replacing the metal plate and seal under there - along with both pipes in the end to get a decent joint.

.

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Just after having my rear caliper changed, as a cheapo britpart! Took about 20 mins, well my mechanic did!

Also noted again the leak from the throttle body area, anyone know how long this takes to do or plate/seal price?

Thanks


P

This is the part I believe. Throttle Body Heater Plate & Gasket MGM000010K Island 4x4 - Specialists in Land Rover and Range Rover Parts and accessories for all models. UK and worldwide mail order.

Parisien said:

Just after having my rear caliper changed, as a cheapo britpart! Took about 20 mins, well my mechanic did!

Also noted again the leak from the throttle body area, anyone know how long this takes to do or plate/seal price?

Thanks


P

Click to expand...

Not sure about part number or price - I can't remember.... I do remember that the seal came with the plate in a little kit.

Fitting was straightforward, but a little fiddly. At least one of my rubber hoses was welded tight on to the plate, so that was a sod to do. Even though mine wasn't straightforward I think it only took about an hour.

My top tips...:
- Make sure you have some good quality hose clips / jubilee clips as spares.
- Get some rubber hose of about the right internal diameter in advance of starting the job.
- Get some PTFE tape handy too. Gas PTFE is thicker, so better if having to pack out a joint.

Gentlemen, thank you again, will order it up and get done at start of next week


P