An overheated engine with a compromised head gasket is often going to be the result of a loss of coolant.
Once the cylinder head gasket leaks then hot gases can over-pressurise the cooling system causing further loss of coolant.
At this point, coolant may enter the sump and contaminate the engine oil resulting in a milky-like-liquid (emulsified oil)
In addition to this, engine oil may enter the cooling system or other parts of the engine internals.
Ultimately the cylinder head will need to be removed and the cause of the ruptured cylinder head gasket should be fully investigated.
If significant coolant loss is experienced then the cylinder head temperature will reach a point where the aluminium will anneal (soften).
Once the cylinder head "goes soft" then the fastener clamping pressure can no longer be maintained.
From experience, removing fasteners from over-heated cylinder head often feels as if the fasteners have not been torqued correctly.
Whilst undoing fasteners and they are easily removed, this is usually the first indication the cylinder head may have been over-heated.
Once the cylinder head has been removed then a hardness test should be carried out at several points along the cylinder head flame face.
A hand held hardness tester such as the TH-170 from SaluTron is ideal for carrying out these measuremets quickly and accurately.
Typical readings for a hard cylinder head will be above 120 Brinell HB and readings for a soft cylinder head will be 35 to 65 Brinell HB.
This hardness tester is ideal for checking aluminium cylinder heads as it is designed to read between 19 and 164 Brinell HB.
Just where in the Lotus Workshop Manual does in stipulate silicon sealant should applied to the camshaft fastener and washer?
Silicon sealant plugs removed from both camshafts which suggests oil may have been leaking from the end of the cams
The front camshaft oil seals need to be removed whilst the rear thrust washer is still fastened in place
Oil seal installation tool on cam nose 
Camshaft oil seal insertion tool
New oil seal successfully installed 
Copyright © 2014 Lotus Marques - All rights reserved.
This material may not be copied, reproduced or published without the expressed written consent of Lotus Marques.
Once the cylinder head gasket leaks then hot gases can over-pressurise the cooling system causing further loss of coolant.
At this point, coolant may enter the sump and contaminate the engine oil resulting in a milky-like-liquid (emulsified oil)
In addition to this, engine oil may enter the cooling system or other parts of the engine internals.
Ultimately the cylinder head will need to be removed and the cause of the ruptured cylinder head gasket should be fully investigated.
If significant coolant loss is experienced then the cylinder head temperature will reach a point where the aluminium will anneal (soften).
Once the cylinder head "goes soft" then the fastener clamping pressure can no longer be maintained.
From experience, removing fasteners from over-heated cylinder head often feels as if the fasteners have not been torqued correctly.
Whilst undoing fasteners and they are easily removed, this is usually the first indication the cylinder head may have been over-heated.
Once the cylinder head has been removed then a hardness test should be carried out at several points along the cylinder head flame face.
A hand held hardness tester such as the TH-170 from SaluTron is ideal for carrying out these measuremets quickly and accurately.
Typical readings for a hard cylinder head will be above 120 Brinell HB and readings for a soft cylinder head will be 35 to 65 Brinell HB.
This hardness tester is ideal for checking aluminium cylinder heads as it is designed to read between 19 and 164 Brinell HB.
Just where in the Lotus Workshop Manual does in stipulate silicon sealant should applied to the camshaft fastener and washer?
Silicon sealant plugs removed from both camshafts which suggests oil may have been leaking from the end of the cams
The front camshaft oil seals need to be removed whilst the rear thrust washer is still fastened in place
Oil seal installation tool on cam nose 
Camshaft oil seal insertion tool
New oil seal successfully installed 
Copyright © 2014 Lotus Marques - All rights reserved.
This material may not be copied, reproduced or published without the expressed written consent of Lotus Marques.
