This was spread across a couple of threads, for simplicity if someone stumbles across it here is the problem and cause.

Hopefully it will be of use

About 1/2 inch loss after 2 or so hours of driving
Coolant loss is from the expansion bottle overflow line.

Rad cap was replaced with a new one
Disco has a 180 Thermostat

Overall Disco Status

• System holds pressure
• While driving temps between 188 and 194 - 1600 to 2300 rpm 20 to 55 Mph
• Idle at traffic light 197 to 201 depending on how much stop and go drops as soon as rpm increases
• Will reach 201 after highway run at traffic light drops immediately once moving
• Hoses remain soft at 194 -197 degs
• System has pressure in the morning normal pfft noise
• No air at bleed screw
• Engine Warm up appears to be normal not excessively fast
• No misfires or codes
• Heater is blowing hot
• no excessive smoke from tail pipe

Cause was a damaged head gasket drivers side front cooling jacket. This damage to the head gasket was a crack in the metal portion of the gasket. See the image below



Tiny crack in the head gasket at about 4:00 from fire ring to cooling gap





Over time you will start to get milkshake, but it may show up in odd places. In my case:

• the filler cap was ok
• I did the PVC mode and it was not ok milkshake in the PVC valve at the intake
• Milkshake in the throttle body from the passenger side breather tube

None of it dribbling huge amounts look like about enough to coat the bottom of a coffee cup.

A couple of further images

 

That over-pressure is the key. I had same issue. I think the HG quality is not the best.....

 

@XRAD interesting that looks like fire ring separation, makes you wonder if Comtec gaskets at $100 US each might be worth it

 

Maybe cometic is the way to go. Not impressed by the strength of fire ring. I did not know cometic were available when I did my heads. I used AB composite. Seems to be one factory making the composite versions which are then sold under various names. The Victor Reinz HG has copper O rings. Cometic can be had from summit racing. I have used VR HG's on plenty of engine builds and the composite material was far superior to the composite in the disco HG's. This may be due to use of TTY bolts in the disco, where my other engine builds were just old fashioned torqued. AB has a vid on HG's, sure most of you have seen it... https://www.roverparts.com/resources...-head-gaskets/

Maybe someone here has used cometic's and can give an opinion?

Choices I found:
AB OEM
AB composite (metal side shown)
VR (which looks like composite w copper O rings, backside shown)
Cometic summit racing C4367-040


AB composite HG

Victor R HG

cometic from Summit racing

 

Highly recommend Cometic all-metal head gaskets for Disco 2.

This is a known fix for a known weakness.






ONLY reinstall with ARP studs, not TTY bolts. Don't exceed 81 foot pounds of torque. Acceptable range is 70 to 81.

 

@No Doubt The new spec sheet with the ARP bolts has the top end torque at 70, man now I have to convince the boss to let me spend another 200.00 CDN

 

My gaskets failed there also.

I think the problem is the bolt holes are too far inboard and the added pressure pushes that section out which causes the fail.

 

Slightly off topic but I don't recall you mentioning, was the oil separator in your right hand valve cover clogged? Or was that how the milkshake got into the throttle body?

 

@Dave03S It was but I did the PVC mod a few months back. Most likely a bad valve seal or 2 letting combustion gas and moisture in to the valve covers

 

I'lll go with cometic next engine rebuild.....