overheating- 1964 2.5 V8 Daimler

[cross]

I have a long term overheating problem - the car overheats progressively over a long distance (non-stop dual carriageway/motorway) up to and at about 100 (repeat 100) miles.
I have addressed all the usual possible causes (incl. gauge & sender unit) and am left with only 2 probables - namely - possibly the early showing of a head gasket problem or intermittent water pump impellor problem.
My question - how can I establish with certainty that there is a head gasket problem and how can I identify which head is affected ?
Oil looks clean and feels uncontaminated - no emulsion in oil or oil filler cap - no water loss , no whiff of exhaust gases in the rad etc.
I am a reasonably competent DIY but have no compressor
Any advice will be much appreciated

[Moomin]

Hi there Cross

I am currently going through a protracted trauma with head gaskets and overheating with my V8 and am desparately trying to get it sorted for Thoresby.

I would suggest that a compression test is the best way to determine if it is a head gasket failure or not. As a start though I'd suggest whipping the plugs out and having a look. My problem is the usual enlarged waterways breaching into the combustion chamber which started to show up as hot running but not boiling over although it doesn't seem as intermittent as yours. When I took the plugs out one was noticeably clean whereas the others were black and dry - rich running which may be a jet problem in the carbs a task for another time! The extent of my problem was only realised once the heads were off though.

If it is a head gasket job, don't be put off. I had never done one before this and it is actually really easy you just have to be methodical and keep everything surgically clean when putting it back together. I will be doing mine again once I have a replacement cylinder head as the original I had repaired failed again within 30 miles, which was disappointing.

Mike

[cross]

Hi Mike,
many thanks for your reply - I assume you did both heads ?
Are you saying that a compression test will indicate definitively head gasket(s) problem ?
I have had the heads off before in 1996 when I restored the car (engine out) and a couple of years ago (in situ) for valve stem seals... but as I am old and wrinkled now , my joy in DIY is not as intense as it used to be .....although it does not over-ride my reluctance to pay someone to do something I can do my self !!!!!

Colin

[Moomin]

Hi Cross

I did do both heads, although there was nothing wrong with the driver's side head. A compression test will tell you whether you have a loss of compression in one or more cylinders, which could be either head or head gasket defects or failure of the piston rings and seals. If it is piston rings then you are less likely to get overheating and you wil be aware of the loss of oil. So a loss of compression coupled with overheating and no excessive oil consumption would be highly indicative of head gasket or cylinder head failure around the cylinder(s) with reduced compression.

Don't suppose you know of anyone with a spare half decent passenger side cylinder head that would be useable whilst I get the original one repaired woud you??

Mike

[alanhack2]

The usual causes of overheating are 1 faulty viscous fan coupling, a quick check for this is switch off engine and observe fan, if it carries on rotating the coupling is faulty, should stop almost immediately. 2 Radiator, its common for the radiator core to be blocked and not cooling efficiently after high mileages. 3 Lastly and more serious is corrosion in the heads and block which is usually due to the lack of a good antifreeze/corrosion inhibitor in the life of the engine. My V8 250 which I have restored recently was cured by fitting a new viscous coupling for the fan. You can use one from the XJ6.

Regards: Alan