P38A Odd coolant issue, coolant refills itself? Any ideas?

ShaneM · Nov 11, 2019

Evening everyone, I'm fairly new to Range Rovers and haven't posted much here before so hello!

I'm hoping someone a bit more knowledgable with these V8s can help.

My RR is a 4.0 v8 p38 gems and it had a small overheat the other day in heavy stop and go traffic. I let it cool off and then drove it home (less than 500m) and the temp didn't rise.

The next day I went out and checked the usual things and noticed the coolant was very low so I topped it up and bleed the system. It's running fine now with no overheating but I notice it is losing coolant.

The odd part is that when I unscrew the cap of the expansion to top it up there's a loud hiss and the thing fills itself from elsewhere in the system.

What's going on?

Any help appreciated.

Datatek · Nov 11, 2019

ShaneM said:
Evening everyone, I'm fairly new to Range Rovers and haven't posted much here before so hello!

I'm hoping someone a bit more knowledgable with these V8s can help.

My RR is a 4.0 v8 p38 gems and it had a small overheat the other day in heavy stop and go traffic. I let it cool off and then drove it home (less than 500m) and the temp didn't rise.

The next day I went out and checked the usual things and noticed the coolant was very low so I topped it up and bleed the system. It's running fine now with no overheating but I notice it is losing coolant.

The odd part is that when I unscrew the cap of the expansion to top it up there's a loud hiss and the thing fills itself from elsewhere in the system.

What's going on?

Any help appreciated.

If you unscrew the cap when the engine is hot, it releases pressure and the water boils which is why it gushes out.
Coolant loss is often leaking leaking O rings on the connections to the heater matrix. Check the carpet and underlay in the drivers footwell.
Overheating is often due to a duff viscous fan, you can test this by inserting a tightly rolled newspaper into the fan blades with the engine up to temperature and idling. If you can stop the fan it's knackered.

ShaneM · Nov 11, 2019

Datatek said:
If you unscrew the cap when the engine is hot, it releases pressure and the water boils which is why it gushes out.
Coolant loss is often leaking leaking O rings on the connections to the heater matrix. Check the carpet and underlay in the drivers footwell.
Overheating is often due to a duff viscous fan, you can test this by inserting a tightly rolled newspaper into the fan blades with the engine up to temperature and idling. If you can stop the fan it's knackered.

Evening Datatek, that's the odd part. It's hissing and "refilling" from nearly empty up to the cold level when completely cold.

The drivers footwell is bone dry and the viscous fan seems solid enough. It's got no wiggle or wobble that might indicate issues further in.

wammers · Nov 12, 2019

You have an air lock somewhere in the system. When header tank pressure is released the airlock expands and forces coolant back into the header tank.

Datatek · Nov 12, 2019

ShaneM said:
Evening Datatek, that's the odd part. It's hissing and "refilling" from nearly empty up to the cold level when completely cold.

The drivers footwell is bone dry and the viscous fan seems solid enough. It's got no wiggle or wobble that might indicate issues further in.

No wiggle or wobble as you put it does not indicate the viscous fan is OK, you need to do the newspaper test.

brianp38dse · Nov 12, 2019

If the viscous fan is working you should here it roar mine sounds like a tank

Saint.V8 · Nov 12, 2019

VC should only roar when either over hot or for a few seconds on cold start.....if it roars all the time, the VC is duff.

Henry_b · Nov 12, 2019

Stick ya fingers in it.

If it takes them clean off, cross that off the list.

If not, change it.

ShaneM · Nov 17, 2019

Datatek, you were correct. I had a massive air bubble. Now cured and running just fine. I'm going to keep an eye on that coolant tank though. I must be losing it somewhere.

wammers · Nov 17, 2019

ShaneM said:
Wammers, you were correct. I had a massive air bubble. Now cured and running just fine. I'm going to keep an eye on that coolant tank though. I must be losing it somewhere.

Sorted that for you.

Datatek · Nov 17, 2019

wammers said:
Sorted that for you.

ShaneM said:
Wammers, you were correct. I had a massive air bubble. Now cured and running just fine. I'm going to keep an eye on that coolant tank though. I must be losing it somewhere.

Really sorted now

wammers · Nov 17, 2019

Datatek said:
Really sorted now

P38A Odd coolant issue, coolant refills itself? Any ideas?

ShaneM

New Member

Datatek

Well-Known Member

ShaneM

New Member

wammers

No longer with us, RIP

Datatek

Well-Known Member

brianp38dse

Well-Known Member

Saint.V8

Dyed-in-the-wool 100% RR Junkie

Henry_b

Think outside, no box required.

ShaneM

New Member

wammers

No longer with us, RIP

Datatek

Well-Known Member

wammers

No longer with us, RIP

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