4.6 P38 Cooling System Nightmare

[Low Down And Dirty]

If this looks familiar to anyone, it is on a couple of other Forums so as much as appreciate your input you can save you fingers by not replying, LOL.

I have a cooling system nightmare, I am not ruling out the fault of a slipped liner (although the engines only done 34k) but I would like to see if any one elce thinks theres another reason, I have the following problems;

- Water loss, some times I worse than others.

- High pressure in the cooling hoses.

- The bottom of the rad is stone cold, feeling the rad when it's upto temp it gets progresively colder as I work my way down and if I flush it through with a hose it seem to have plenty of flow and I have changed the thermostat.

- And possably totaly unrelated but the interior heaters give out no heat untill I am moving.

- I have not as yet pressure tested the cylinders. But been told that this will not prove anything, although I thought it would at least prove there is no gasses escaping from any of the pots.

- I have no power loss

Thanks in advance for any help.

I am planning on removing the Rad at the weekend because I have had a couple of people suggest that the fault lies there.

[Bull Bar Cowboy]

I cant quite understand why the bottom of the rad is cold if you have checked the flow ?

However, a good check for a porous block to liner seal is to remove the plugs after a good hot run and see if any of them look to be steam cleaned ………. also you can easily wipe the deposits from a faulty cylinder plug with a rag to leave the plug looking new…….

Another good test is to go for a good hot run and the then stop for 5 minutes …….. restart the hot engine and look for white / grey exhaust smoke that will clear quite quickly……….this is caused by the fact that the coolant system will have built up high pressure from the hot run (combustion gases into the coolant) and once you stop, the coolant system will release some of its pressure at the point of the leak, which is the combustion chamber……… when you restart (before the released coolant has had chance to drain away) the coolant is burnt off …….. sometimes its accompanied by a slight misfire.

On a cold engine, remove the coolant cap and smell the coolant ……… often it will smell strongly of exhaust fumes if you have a liner / head gasket problem.

A compression test will definitely show up a head gasket failure, but it will not show up a block to liner seal problem……..

Ian

[David Sparkes]

"And possably totaly unrelated but the interior heaters give out no heat untill I am moving. "

To me, this suggests air in the system, that isn't being flushed out of the matrix until you get the increased flow that comes with higher heat input and faster pump operation, consistant with driving the car.

"Water loss, some times I worse than others. "

Air in the system, expanding as it warms, sometimes sufficiently to push coolant out of the oveflow. Set up a bottle / tank to collect whatever comes out of the overflow to prove this is where the coolant is going.

"- High pressure in the cooling hoses. "

Air in the system, acting as described above.

Are you bleeding the system correctly? In particular are you blowing through the small diameter pipe that leads from the top RH corner of the radiator (near the battery) to the expansion tank?

Do you then run the engine, with the cap off the expansion tank, and the small hose disconnected, until you get a good flow of coolant from the radiator stub pipe?

At this point both pipes to / from the matrix should be warm if not hot.

Do you then attach the small pipe back to the radiator stub and check for a good flow of coolant into the expansion tank? (Use a torch or put the bonnet vertical to give clear visibility).

This should ensure all air is cleared.

If the problem reoccurs you are looking for a source of air into the cooling system.

HTH.

[Roverdrive]

I would look to the correct bleeding of the air out of the system, and once this is done, re check the radiator temperature.

To my way of thinking, if the radiator is cold at the bottom, there is a reduced colant flow through it, allowing it to be " overcooled" if you like.

Are there known issues with the water pump impellers failing on these engines?

[Low Down And Dirty]

I seem to be getting a lot of people suggesting that it is an air lock so I will have to try bleeding it again at the weekend.

Bleeding the system I rad the engine with the cap off untill the system settled at the cold fill level, I made sure the rad bleed pipe was clear before I did this, it is acctually mentioned in the RAVE manual I noticed so assumed it may be a regular fault thats easily missed, the hoses to and from the matrix get HOT.

[q-rover]

Another trick would be to park the car on a steep slope (engine high)

whilst bleeding.

[FridgeFreezer]

Just 'cos you've changed the stat don't assume it will work - I did this and the new one stuck too there was no bleed-by hole in the stat body so it formed a small airlock and then refused to open, despite the fact that if you boiled the stat in a pan of water (a common check) it would open fine.

[David Sparkes]

Earlier you said "the interior heaters give out no heat untill I am moving. " and I surmised air in the matrix.

Now you say "the hoses to and from the matrix get HOT.", but is this during filling and bleeding the system? If so, I'm not too surprised as the system is designed to circulate coolant via the heater matrix BEFORE the thermostat opens.

However, if the hoses to and from the matrix get HOT during filling & bleeding, AND the interior heaters give out no heat until you are moving, then there is another problem.

This could be that the interior fans aren't starting up straight away. The detail control comes from the HEVAC ECU programme, but there is an overall control by a thermostat attached to the solid matrix pipework within the cabin. If this has fallen off or become dislodged, or failed within itself, it will not tell the HEVAC ECU there is heat to be used, so the ECU keeps the fan speed low.

There are pictures about this thermostat on the RangeRovers.net site.

Another possible cause is that the interior temperature sensor is 'insulated' by fluff, and thus giving a misleading reading to the HEVAC ECU. This sensor is behind the grill, beneath the clock. Use a torch and 'bent pin' to look behind the grill and hook out any fluff. The sensor is a small bead. There is also a fan with a drum style (not propellor style) blade. Your hook should rattle against this when the ignition is on. If you cannot see or hear this fan (engine not running, ignition on) then that's another problem that will affect the HEVAC response.

It's also possible, but I regard it as an outside possibility, that the blend flaps are sticking slightly in a 50/50 hot / cold position, that they were in when the last journey stopped, whereas at start up in cold conditions they should drive immediately to full hot. You should hear the gear noise of this movement when you first switch on the ignition. I'd be surprised the 'flap sticking' problem exists without giving you the chequebook symbol with 30 seconds of starting the engine.

You may be able to pick up on other HEVAC behavoir problems or 'characteristics' that back up one of other of these problems.

HTH

[David Sparkes]

"Just 'cos you've changed the stat don't assume it will work "

A valid point, but bad news. Have you seen the price of a 38A 4.0/4.6 V8 thermostat octopus?

Paddock Spares doesn't list one, Rimmer Bros charge over £52.00 inc VAT http://preview.tinyurl.com/22wafg

Cheers.

PS, Just spotted they do a cheap version at less than £25.00!! http://preview.tinyurl.com/22sm3k

[Low Down And Dirty]

Both the old and the new stat work fine 'cause I have checked them off the car, I bought the new stat direct for Land Rover £49

I was myself under the impression that the heater problem was totaly unrelated to the other problem, just coincadental that it's happened at the same time.

Not had chance to play about with this since last weekend, planning on trying it again tomorrow, going to remove most of the hoses and try pressuring some water round with a hose just to make sure there is no form of blockage, and then removing the header tank from where it sits and putting it as high as I can then try bleeding the system once more.

If that dosn't work them I am going to remove the cylinder heads as I was planning on upgrading to a pair of big valve ported and pollished ones anyway at some point, and see if there's anything untoward there.

[H-M3]

Hi and sorry to jack this thread did you manage to solve this problem? coz I have the late p38 4.6 my temp needle was going up towards the red mark and also I only get warm air until I drive the car. I have realised that the coolant level was quite low so I have topped it up apprx 2 litres, do you think this might have been the cause, low coolant? Is it normal to lose coolant over certian time?

Thanks again, also I forgot to mention how much coolant do I need to put in for a complete drained system? Its been 2 years since it had a coolant change. Also would you recommend stealers only coolant or any other? if LR then what colour????

Thanks

[Low Down And Dirty]

Vaccum tested the system to -24psi with an air lift kit eariler and the pressure held for 20 mins with absolutly no drop in the vaccum, refilled the cooling system through the airllift kit and ran it on my drive for about 30 mins, with no loss of coolant, took the truck out for a 10 mile drive and lost ½ the fluid from the header tank.

This is getting annoying. now.

[Low Down And Dirty]

I only get warm air until I drive the car.

I sorted this problem the blend flaps were sticking, I noticed the cheque book sign coming up when the problem happened.

how much coolant do I need to put in for a complete drained system? Also would you recommend stealers only coolant or any other? if LR then what colour????

I used LR Extended life coolant, Pink. But it is expensive, unless you know people

Full system drain is 11.3 l apparently.

[Low Down And Dirty]

Since I've left it to cool down the water has come back up to the cold fill level, is it normal for the fill level to go down when the system is at running temp ?

[Bowie69]

Yep.... the hoses etc expand more than the water does, so pretty normal.

[Low Down And Dirty]

Exactly what I wanted to here. I was a bit confused because most cars the water in the header tank goes up when it gets up to temp.

Although most manufacturers aren't stupid enough to put the top hose higher than the header tank !

[Bull Bar Cowboy]

Vaccum tested the system to -24psi with an air lift kit eariler and the pressure held for 20 mins with absolutly no drop in the vaccum, refilled the cooling system through the airllift kit and ran it on my drive for about 30 mins, with no loss of coolant, took the truck out for a 10 mile drive and lost ½ the fluid from the header tank.

This is getting annoying. now.

Often a porous bore will only show up on a hot engine .........................

Ian

[Low Down And Dirty]

Often a porous bore will only show up on a hot engine .........................

It is a later type D60 block so porous bore should be out of the question due to the fact it has liners.

[*-jester-*]

Have you tried a new radiator? I've read elsewhere that they are prone to clogging up.

I'm having overheating problems myself with my 1998 P38 4.0 so I'm about to do some deep investigations of my own.

[FridaT]

It is a later type D60 block so porous bore should be out of the question due to the fact it has liners.

Indeed the block has liners but still the same Rover liners as the earlier V8 engine type. To suggest that a porous bore should be out of the question is untrue.

It is actually the block casting which cracks behind one or more of the liners, resulting in water pumping and sucking over the top.

We have supplied exchange engines for a good number of the later type V8 engines.

FridaT

www.turner-engineering.co.uk/html/V8engines.html

[DEANO3528]

Hello and Welcome Frida. Nice to see you on here.

[TomG]

Isn't there a common problem with some leak from the heater matrix on the P38? Seals or something like that around the passenger footwell area?

May be worth a check

[q-rover]

Wet passenger (LHD) = O-rings, = keyhole surgery or dash out.

[keithjh]

[

I have a cooling system nightmare, I am not ruling out the fault of a slipped liner (although the engines only done 34k) but I would like to see if any one elce thinks theres another reason, I have the following problems;

Mine had only done 35K when it went, and that was on a new engine first one lasted 76k---now have a TD6!!

Keith

[paintman]

What was the result of the testing of the coolant for the presence of combustion gases as suggested on another forum?