Disco 2 Head Gasket and Heater Core

2003 Discovery 2 Td5 (face-lift model with 16P engine)
Engine number: 16P11184A

Noticed around nine months ago that there was a small amount of coolant leaking under the top coolant hose area on the front passenger side of the engine (RHD):



The top hose was also a bit hard, and I suspected therefore some exhaust gas was probably escaping into the coolant side via the head gasket (original engine and head gasket) and over-pressurising/over-heating the cooling system after 280,000kms on the clock. The engine oil is perfect on the dipstick - looks and smells like oil (no diesel smell or creamy emulsion). There is also no oil in the coolant expansion tank - the coolant looks perfect and has no other smell other than the normal OAT coolant smell (I didn't chemically test it for presence of CO2). The fuel cooler isn't leaking (I previously repaired).

The coolant leaks got a little worse until the point where, when the engine was turned off after a drive, around 250mL of coolant would leak out under the engine. I topped-up the expansion tank for a while, but I recently decided to take some action when the leak was more like 500mL.

I bought a bottle of Rislone Head Gasket Fix to buy some time while I find/buy all the correct parts (gaskets/bolts/etc.) and look at the procedure for installing a new head gasket!

The Rislone product uses, as one ingredient, sodium silicate - it fuses into a hard glass/ceramic on contact with the very high temp exhaust gas, otherwise it remains dissolved in solution. Followed the procedure on the bottle (add directly into the expansion tank) and within ten minutes of idling the head gasket was sealed - running well now for just over a fortnight (one long round-trip of c.500km with several long hills) with no coolant leaks.

There was one problem - the heater now doesn't blow hot air any more. I did turn the heat up to Hi and the fan on full when the Rislone was added (as per bottle instructions), but obviously one or more of the other ingredients, other than the sodium silicate, has caused a blockage at the heater end. I contacted Rislone and they said that I should do a back-flush of the heater core with compressed air or water. They said there could be a blockage somewhere or a heater control valve could be blocked/stuck - they said it can happen based on the design of the heater and/or heater control valve.

So, hoping some here might have advice re several questions I have, and any experience to pass on:

1. How can I tell which head gasket I should purchase for my engine (I was asked "how many holes"?)?

2. Any recommendations re head gasket replacement kits I can purchase online (Australia or UK)?

3. Any good procedures/tips out there that someone can particularly recommend, both for replacing the head gasket and rectifying the heater?

4. Any special tools I'll need to get hold of to replace the head gasket (apart from my socket set and ratchets)?

5. Is there a valve that controls flow through the heater - didn't see anything in RAVE?

Thanking you all in advance for any advice/tips.

1. The number of holes punched in the edge of the gasket refers to the gasket thickness. There are 3 available I believe. There is a bit of protruding gasket that you can see somewhere around the head but I can't remember where. You'll be able to see how many holes are in it.

3. Follow the procedure for head gasket replacement in the workshop manual. The manual comes in the form of a CD known as "RAVE". You'll need to hunt around a fair bit to find an ISO image to download and burn to CD. (Can't help with the heater I'm afraid).

4. A torque wrench if you don't have one.

There are no valves in the cabin heater circuit, i.e. it is constant flow. But what you describe is very symptomatic to an airlock or perhaps combustion gases that were trapped in the coolant circuit and now cannot escape as the gasket is sealed. I would first bleed the cooling system and see if the situation improves, given that if coolant is not flowing through the heater matrix won't get resolved by replacing the head gasket.

https://www.landyzone.co.uk/land-rover/bleading-td5-cooling-system.98725/

Quote: “They said there could be a blockage somewhere or a heater control valve could be blocked/stuck - they said it can happen based on the design of the heater and/or heater control valve.”

Your vehicle’s heating system is Air Blending so the matrix is hot all the time, depending on the engine coolant temperature of course, so no valve and therefore not shown, the cabin temp and air flow direction is adjusted by dampers.

The D1 has a similar heating system but it appears that the D2 in-line thermostat can have issues sometimes re heater temp, there’s already a thread or two on that subject somewhere… but I wasn’t that interested

Intestinalworm said:

2003 Discovery 2 Td5 (face-lift model with 16P engine)
Engine number: 16P11184A

Noticed around nine months ago that there was a small amount of coolant leaking under the top coolant hose area on the front passenger side of the engine (RHD):

View attachment 266055

The top hose was also a bit hard, and I suspected therefore some exhaust gas was probably escaping into the coolant side via the head gasket (original engine and head gasket) and over-pressurising/over-heating the cooling system after 280,000kms on the clock. The engine oil is perfect on the dipstick - looks and smells like oil (no diesel smell or creamy emulsion). There is also no oil in the coolant expansion tank - the coolant looks perfect and has no other smell other than the normal OAT coolant smell (I didn't chemically test it for presence of CO2). The fuel cooler isn't leaking (I previously repaired).

The coolant leaks got a little worse until the point where, when the engine was turned off after a drive, around 250mL of coolant would leak out under the engine. I topped-up the expansion tank for a while, but I recently decided to take some action when the leak was more like 500mL.

I bought a bottle of Rislone Head Gasket Fix to buy some time while I find/buy all the correct parts (gaskets/bolts/etc.) and look at the procedure for installing a new head gasket!

The Rislone product uses, as one ingredient, sodium silicate - it fuses into a hard glass/ceramic on contact with the very high temp exhaust gas, otherwise it remains dissolved in solution. Followed the procedure on the bottle (add directly into the expansion tank) and within ten minutes of idling the head gasket was sealed - running well now for just over a fortnight (one long round-trip of c.500km with several long hills) with no coolant leaks.

There was one problem - the heater now doesn't blow hot air any more. I did turn the heat up to Hi and the fan on full when the Rislone was added (as per bottle instructions), but obviously one or more of the other ingredients, other than the sodium silicate, has caused a blockage at the heater end. I contacted Rislone and they said that I should do a back-flush of the heater core with compressed air or water. They said there could be a blockage somewhere or a heater control valve could be blocked/stuck - they said it can happen based on the design of the heater and/or heater control valve.

So, hoping some here might have advice re several questions I have, and any experience to pass on:

1. How can I tell which head gasket I should purchase for my engine (I was asked "how many holes"?)?

2. Any recommendations re head gasket replacement kits I can purchase online (Australia or UK)?

3. Any good procedures/tips out there that someone can particularly recommend, both for replacing the head gasket and rectifying the heater?

4. Any special tools I'll need to get hold of to replace the head gasket (apart from my socket set and ratchets)?

5. Is there a valve that controls flow through the heater - didn't see anything in RAVE?

Thanking you all in advance for any advice/tips.

Click to expand...

1. I just bought the 3 hole and fitted that one regardless (its not a racing engine)
2. I just purchased a head gasket and some steel dowels. If its gone it may be the dowels need replacing with steel ones.
3. I reused the old head bolts. Don't understand why people replace them, they are pre-loaded within their elastic yield strength and i'm not aware of any in service fatigue failure. The head is bloody heavy so I used an engine lift to help move it into and out of place.
4. Not that I can remember, though I do recall buying those special pipe clip pliers to get the hoses off.
5. When my head gasket was going the heater not working was one of the symptoms due to water loss or air trapped. I just cleaned everything out, replaced the thermostat and housing and other bits tucked down the rhs of the rad at the bottom.

Its a bit time consuming but not technically difficult. Best doing it sooner rather than later in case you warp the head or cause more significant damage.
Mines been perfect now for many years as a daily driver.

DefenderPilot said:

1. The number of holes punched in the edge of the gasket refers to the gasket thickness. There are 3 available I believe. There is a bit of protruding gasket that you can see somewhere around the head but I can't remember where. You'll be able to see how many holes are in it.

3. Follow the procedure for head gasket replacement in the workshop manual. The manual comes in the form of a CD known as "RAVE". You'll need to hunt around a fair bit to find an ISO image to download and burn to CD. (Can't help with the heater I'm afraid).

4. A torque wrench if you don't have one.

Click to expand...

Thanks for that - will have to have a closer inspection regards these holes - so assuming if I take the acoustic cover off I should be able to find some protruding gasket somewhere?

I have RAVE - have used it before - will use that then as a guide!

Might be okay with tools then, I do have a torque wrench.

NPG said:

There are no valves in the cabin heater circuit, i.e. it is constant flow. But what you describe is very symptomatic to an airlock or perhaps combustion gases that were trapped in the coolant circuit and now cannot escape as the gasket is sealed. I would first bleed the cooling system and see if the situation improves, given that if coolant is not flowing through the heater matrix won't get resolved by replacing the head gasket.

https://www.landyzone.co.uk/land-rover/bleading-td5-cooling-system.98725/

Click to expand...

Heater was working perfectly just a minute before the Rislone was added with the fan on high; 4-5 minutes after the Rislone liquid was added to the expansion tank (which was already 1/2 full), the air coming out of the heater went cool. I can't understand how air/exhaust gas could be trapped in the heater core? There is no leaking of coolant now at all and all running well.

l

Bantam1 said:

1. I just bought the 3 hole and fitted that one regardless (its not a racing engine)
2. I just purchased a head gasket and some steel dowels. If its gone it may be the dowels need replacing with steel ones.
3. I reused the old head bolts. Don't understand why people replace them, they are pre-loaded within their elastic yield strength and i'm not aware of any in service fatigue failure. The head is bloody heavy so I used an engine lift to help move it into and out of place.
4. Not that I can remember, though I do recall buying those special pipe clip pliers to get the hoses off.
5. When my head gasket was going the heater not working was one of the symptoms due to water loss or air trapped. I just cleaned everything out, replaced the thermostat and housing and other bits tucked down the rhs of the rad at the bottom.

Its a bit time consuming but not technically difficult. Best doing it sooner rather than later in case you warp the head or cause more significant damage.
Mines been perfect now for many years as a daily driver.

Click to expand...

Thanks for all that info.

Assuming "three holes" is the thickest of the three gaskets? I was told (based on VIN) that the dowels would definitely be steel?

Heater, not sure there, Rislone told me to backflush with air or water - they said blockage sometimes happens depending on the design of the heater core. The heater has been perfect since 2003 (never missed a beat) and then the air suddenly went cool like a few minutes after topping-up the expansion tank with Rislone. Coolant didn't drain out/leak out at any time and the coolant level hasn't changed for a fortnight (some long return trips there) - just cool air now?

Anyway, looks like I'll have to order the parts now to do the head gasket and then also flush the (blocked?) heater core - any suggestions where I can get a complete head gasket kit?

discool said:

Quote: “They said there could be a blockage somewhere or a heater control valve could be blocked/stuck - they said it can happen based on the design of the heater and/or heater control valve.”

Your vehicle’s heating system is Air Blending so the matrix is hot all the time, depending on the engine coolant temperature of course, so no valve and therefore not shown, the cabin temp and air flow direction is adjusted by dampers.

The D1 has a similar heating system but it appears that the D2 in-line thermostat can have issues sometimes re heater temp, there’s already a thread or two on that subject somewhere… but I wasn’t that interested

Click to expand...

So, you're saying it could be the big in-line thermostat down near the bottom of the radiator that may not be fully opening perhaps? Must admit - didn't see anything really in RAVE about the heater / heater core; the blended air ratio heating makes sense - so warm coolant should be going through the heater core all the time?

Bantam1 said:

1. I just bought the 3 hole and fitted that one regardless (its not a racing engine)
2. I just purchased a head gasket and some steel dowels. If its gone it may be the dowels need replacing with steel ones.
3. I reused the old head bolts. Don't understand why people replace them, they are pre-loaded within their elastic yield strength and i'm not aware of any in service fatigue failure. The head is bloody heavy so I used an engine lift to help move it into and out of place.
4. Not that I can remember, though I do recall buying those special pipe clip pliers to get the hoses off.
5. When my head gasket was going the heater not working was one of the symptoms due to water loss or air trapped. I just cleaned everything out, replaced the thermostat and housing and other bits tucked down the rhs of the rad at the bottom.

Its a bit time consuming but not technically difficult. Best doing it sooner rather than later in case you warp the head or cause more significant damage.
Mines been perfect now for many years as a daily driver.

Click to expand...

Interesting you had to use an engine lift? It's an aluminium head, does anyone know the weight - I just assumed less than 30kg?

Intestinalworm said:

Heater was working perfectly just a minute before the Rislone was added with the fan on high; 4-5 minutes after the Rislone liquid was added to the expansion tank (which was already 1/2 full), the air coming out of the heater went cool. I can't understand how air/exhaust gas could be trapped in the heater core? There is no leaking of coolant now at all and all running well.

l

Click to expand...

I was hoping that it would be an airlock and therefore a minor issue. But from what you describe here, it looks like the sealer clogged the heater matrix in spite of the assurances given by the product manufacturer that this wouldn't happen. I could be wrong but I believe there is a way to pressure flush just the heater matrix through its hoses running in the engine bay. And since the leak has stopped, I would also replace the entire coolant before Rislone decides to block somewhere else.

Just noticed Page 26-1-4 of RAVE shows the coolant pathway through the heater matrix - interestingly the diagram shows the heater matrix inlet hose clearly positioned below the heater matrix outlet hose - both going in through the bulkhead/firewall. When I looked at my engine it looked like this:



The hoses are pretty much alongside one another. The inlet (1) to the heater matrix comes from the passenger side of the engine, and the outlet (2) from the heater goes to the fuel cooler. Is that correct? If so, then I backflush with compressed air or flush with water through (2) and out (1). All good?