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trickster5000

Member Since: 12 Dec 2015
Location: East Yorkshire
Posts: 487

Cracked cylinder head?

Hi,

To give background: Bought a 300tdi for 50 quid last summer with absolutely no history/info. Chucked it in my 90 and it's been running flawlessly for the last yr covering approx 5k miles but pretty much all less than 30 mins and no motorway.

Yesterday, I went laning in the Dales which involved a decent stretch of motorway driving to get there. On the motorway on the way home the temp went into the red and it spat out all its coolant through the expansion cap. We weren't far off home so just chucked some more water in and gently drove home at no more than 50 ish. By the time we got home it had yet again spat out all the coolant.

I took the head off today and found this:

Click image to enlarge

Click image to enlarge

Cylinders 2 & 3 look to have cracks from the glow plugs and cylinder 4 looks to have a crack between the injector and one of the valves.

Additionally there are marks from the water jackets to the cylinders:

Click image to enlarge

Do these pictures look characteristic of cracked 300 heads? Is a cracked head effectively scrap metal? Where's the best/cheapest place to get a recon or brand new head? Matt.

'89 90 CSW with a 3.5 V8 conversion (WIP) - http://www.defender2.net/forum/topic46809.html

8th Jul 2018 3:14pm

trickster5000

Member Since: 12 Dec 2015
Location: East Yorkshire
Posts: 487

I've now had a better chance to have a look at the gasket and the block and it looks like the HG failed around the triangular-ish water jacket between cyl 2 and 3. This would explain the coolant pressurisation.

Additionally the small coolant hose that goes into the thermostat housing was completely blocked with cruddy deposits which means exhaust gases in the system from the HG failure wouldn't bleed properly causing air locks and overheating.

Before I spend £300+ on a new head I'm going to put a new gasket set on and just see if that fixes the coolant pressure problems for now and worry about the suspected head cracks when the symptoms arise. Matt.

'89 90 CSW with a 3.5 V8 conversion (WIP) - http://www.defender2.net/forum/topic46809.html

8th Jul 2018 10:26pm

Mariner

Member Since: 03 Oct 2017
Location: Arklow
Posts: 127

While you have the head off you may as well have it pressure tested.
The engineering shop will determine if it is cracked and they can clean up the mating surface. Not expensive and could save you some bother.

9th Jul 2018 1:53am

Procta

Member Since: 04 Dec 2016
Location: Sunderland
Posts: 4932

trickster5000 wrote:
I've now had a better chance to have a look at the gasket and the block and it looks like the HG failed around the triangular-ish water jacket between cyl 2 and 3. This would explain the coolant pressurisation.

Additionally the small coolant hose that goes into the thermostat housing was completely blocked with cruddy deposits which means exhaust gases in the system from the HG failure wouldn't bleed properly causing air locks and overheating.

Before I spend £300+ on a new head I'm going to put a new gasket set on and just see if that fixes the coolant pressure problems for now and worry about the suspected head cracks when the symptoms arise.

I wouldn't bother doing that, id just get the lot sorted out. You don't want to be pulling it to bits again. Defender TD5 90 ---/--- Peugeot 306 HDI hatch back

Success is 90% Inspiration and 4 minutes Preparation # you can make it!

17th Jul 2018 6:12am

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