Probably cylinder head gasket again

I'm experiensing blow-outs from the cooler tank.

I'm monitoring the coolant temp with Hawkeye and I have also a water temperature gauge on the lower radiator hose, just ahead of the In-line Thermostat to monitor when the thermostat opens.
The monitored engine temp rises to 103°C and drops to 97°C beause I'm lowering the speed, and rises again…
The temp on the lower radiator outlet ahead of the thermostat is only 20°C.
The thermostat doesn't open!
I have boiled the thermostate and it's ok.
I've also tried 2 other thermostats.
Same result.
I have replaced the coolant pump.
Same result
I have replaced the entire radiator.
Same result.
I have replaced the thermostat with a tube and blocked the bypass, causing the coolant to flow through the radiator.
Then the temperature raised to max 85°C and there were no blow-out.
I have tested the Cylinder leak, and they're between 20-35% None of them are causing bubbles in the cooler tank...

I haven't checked for CO in the coolant yet, but I can't find any other solution than a blown head gasket or cracked cylinder head.

It it correct that if the pressure in the coolant system is too high (like from a HGF), the thermostat refuses to open?

What do the experts say?

have you bled the cooling system properly?

seriously they are a pain to bleed fully and if not done fully it will give you these symptoms.

I can promise it's bled.
And bled again and again and...
It's my 6th. 18K4 engine that I have rebuilt...
Did a combustion CO##₂ in coolant test, and after a loong time and the engine running at relatively high rev. temperature rising towards 80°C on the hawkeye, I finally managed the monitoring fluid to change color from clear blue to green. Not yellow, but green. So there is a little CO₂ in the coolant.
There was nothing until the temperature was getting higher.
so now I have to tear off the cylinder head and inspect. Maybe there is a warped block?
Low liner, or warped or cracked head or if I'm lucky just a broke head gasket.
The engine has been running for about 3000km...
'

hmm :scratching_chin:

other than whipping the head off all i can think of is pressurisation due to inlet manifold gasket.

sorry i can't be of further assistance.

How can that explain CO in the coolant?
I would love to have another solution that ripping off the cylinder head...

it doesn't


can't think of a reason to prevent you removing the head to investigate, sorry.

I'll be back with info.
Does anybody know the answer on this?
It it correct that if the pressure in the coolant system is too high (like from a HGF), the thermostat refuses to open?

Ok, now the cylinder head is off.
Cylinder liner # 3 and 4 is too low in the block.
On the front side (exhaust), they are above the block surface and on the rear (intake) side they are below the surface.
Not mutch, but noticeable.
So I believe it's just to rip out the engine and put on a couple of liner chims...
Another thing is that the cylinder head have scuffs on one side (exhaust) on cylinder # 1, 2 and 3. a little on # 4 too.

Here's a video of the examination of the cylinder head.

looked at the video "Great video" and it does show the liners down probably best if you put new ones in ,I wish I was in a fit state to do those jobs now ,good luck with it

One of the liners (nr 4) are new...
I don't think that's the main problem.
But i have to put in chims (0,05mm) to highen the 3rd and 4th liner...
And probably surface the cylinder head.
jaja (yesyes) I'm eager to put in a engine from Toyota or similar instead of this crap.
I've rebilt so many 18K4 now.
I really hate them from the bottom of my heart.
Someone wrote:
Designed by satan and built by monkeys...

The K series does have a few problems but it can be made reliable.
Has this engine ever overheated? This is the primary cause of liner recession and fire ring recession on the head. If the liners have dropped unevenly then it's well worth having the liner land bored true to the deck face or the GH will never seal correctly.

Hi,
I don't know if it's been over heated, but I assume it has.
It shure need something to be done. I'll pull the engine tomorrow and fit another one instead. Then I'll decide what to do.

royturbodiesel said:

Hi,
I don't know if it's been over heated, but I assume it has.
It shure need something to be done. I'll pull the engine tomorrow and fit another one instead. Then I'll decide what to do.

Click to expand...

If the engine has previously been over heated then the hardening treatment given during manufacture will have been lost. This causes fire ring recession on the head and often liner drop as the land in the block has softened. Your liners have dropped on the exhaust (thrust) side which is the classic symptom of a soft (annealed) block.

Nodge68 said:

If the engine has previously been over heated then the hardening treatment given during manufacture will have been lost. This causes fire ring recession on the head and often liner drop as the land in the block has softened. Your liners have dropped on the exhaust (thrust) side which is the classic symptom of a soft (annealed) block.

Click to expand...

The strange thing is that it isn't as you describe, but the opposite:
On the front side (exhaust), the liners are above the block surface and on the rear (intake) side they are below the surface.
Not mutch, but noticeable.

The cylinder head has not been over heated since we purchased it from Midland Autocare.
The reason they remanufactured the cylinder head in the beginning, I assume is because of over heating...

royturbodiesel said:

The strange thing is that it isn't as you describe, but the opposite:
On the front side (exhaust), the liners are above the block surface and on the rear (intake) side they are below the surface.
Not mutch, but noticeable.

The cylinder head has not been over heated since we purchased it from Midland Autocare.
The reason they remanufactured the cylinder head in the beginning, I assume is because of over heating...

Click to expand...

I'm talking complete rubbish Im to used to differebt engines I guess. On the K series the engine the thrust side is the inlet manifold side not the exhaust side! This would follow liner land recession on the rear of the block.

And to the point: What can be done now?
I can put in some chims but still there will be differrent hights og the liners on ex and in side?
But the fiering rings on the HG will carry the most of that differrence, I believe...
Or?

royturbodiesel said:

And to the point: What can be done now?
I can put in some chims but still there will be differrent hights og the liners on ex and in side?
But the fiering rings on the HG will carry the most of that differrence, I believe...
Or?

Click to expand...

Personally I'd change the block but here in the UK they are plentiful and reasonably cheap. Weather any repair you do on your engine lasts would depend on the hardness of the block. Being heat treated from manufacture it is crucial the engine isn't over heated.
This tells the full story.
Why do head gasket failures occur?

As to the shims working. I've only shimmed 1 block that I knew for any time after the work was done. It lasted a long as I keep the car which was around 20K miles.

What will a block cost in the UK?
I guess that £ 30-50 would be the shipping cost...

2 "new" engines on it's way from UK...
Purchased on eBay
I'm fed up of fixing engines boiled to death.