why does my 302 lose coolant?

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peranaman
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why does my 302 lose coolant?

Post by peranaman »

Hi guys.

Now that the Perana is running and on the road I'm finding and fixing stuff.

One thing that is bugging me big time is this.

The 302 is getting hot. Quite how hot I won't know til I've Thermo gunned it.

These are the symptoms -

1. engine incredibly hot like a furnace.

2. Losing coolant in differing ways I'll explain.

3. Seems like excessive build up of pressure in water system - will explain also.

4. top of rad gets so hot that no matter how much or how little black paint I use it still blisters and melts.

Now the thing is - when it was a standard 'cooking' engine and sadly worn and under powered it never got hot and never lost fluid.

With a 13 lb rad cap the water pushes past the cap and out of the overflow hole.

With a 15 lb cap it seems to do the same but to a lesser extent - i.e. I've not witnessed it spurting out but when I've rested the motor and the electric fans have finished - when I take the cap off it's down of fluid.

With a 20 lb cap on the radiator top tank expands and bulges like it's fit to burst and fluid has still been lost.

Having said all that - I just did a 50 mile return journey having changed back to the 15 lb cap and I only lost about 2 pints - but that's still 2 pints too much.

My coolant ratio is 50% water and 50% blue antifreeze.

The water never seems to boil up and hiss and spit out - well not when stationary anyway. My money would be on some sort of pressure thing.

I have attached some pics showing my hose set up.

The water pump is a relatively new aluminium one suited for a 1971 vintage 302.

The hose connections are different now as I was told the original setup on my car was wrong - funny thing is it never previously lost fluid.

I have been driving like Miss Daisy with occasional blip to overtake and exercise the 302.

The engine spec is - 5 litre with 20 plus pistons Keith Black Hypereutectic pistons. Standard cast heads with new valves and slightly ported. all new gaskets from Summit Rcaing. Duplex timing chain. High capacity oil pump. Holley 570 Avenger carb. Fast road type cam.

Ignition is Accel dizzy with Pertronix breakerless Ignitor system. MSD Blaster 2 coil. 3 inch air filter.

Cosworth electric twin fans - sucking the air through the rad in the right direction!!

Radiator is a 2 year old 5 core beast.

Heater matrix brand new copper / brass.

Timing is 34 degrees.

Plugs NGK Mustang type.

Any thoughts would be gratefully received.

Having searched the Internet it seems that there are loads of possibilities - some of which are scary some are simple but none are conclusive.

I do wonder my water circulation is an issue now The arrows do not necessarily indicate direction of water flow.

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kiwicar
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Post by kiwicar »

Hi
I think you have a blown head gasket. I would avoid running it any more before you have solved the problem as it sounds as if it is getting very hot and this will lead to warped heads, warped block, cracks in the head (especially between valve seat inserts).
was the block decked when you had it re-bored? were the heads checked for being flat? when you have the heads off check for cracks in the block, especially between the cylinders and head bolt holes that are open to the water jacket.
It is quite possible the bloc had a crack that was bunged up with old combustion deposits that were removed by the machining and subsequent cleaning.
Best regards
Mike
poppet valves rule!
katanaman
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Post by katanaman »

I would agree with everything Kiwicar has said. You have a blown gasket or a crack somewhere. You can do a sniffer test to prove this, basically the test changes the colour of a liquid which indicates exhaust gases in the coolant. If this is proven then you have no option other than to strip the engine and find the problem. Could be and hopefully is just a head gasket but with it getting so hot your going to have to check your deck and heads are straight. If that all looks ok then your into crack testing after that. One thing is for sure, you need to stop driving it until you find the problem or your looking at some major damage being done.
peranaman
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Post by peranaman »

katanaman wrote:I would agree with everything Kiwicar has said. You have a blown gasket or a crack somewhere. You can do a sniffer test to prove this, basically the test changes the colour of a liquid which indicates exhaust gases in the coolant. If this is proven then you have no option other than to strip the engine and find the problem. Could be and hopefully is just a head gasket but with it getting so hot your going to have to check your deck and heads are straight. If that all looks ok then your into crack testing after that. One thing is for sure, you need to stop driving it until you find the problem or your looking at some major damage being done.
I admit it does sound like that, however, with a temp gauge that must have the wrong sender unit I cannot accurately see what temp I have.

I have re-plumbed the hoses back to original and will test again - thanks and will update later.

Incidentally if anyone knows how to get a standard Capri 3.0 litre temp gauge working with the correct colour coded sender unit please tell me - I've tried a black and a white but only the white seems to send any voltage at all - but the gauge never gets beyond the Blue or Cold on the gauge - but it does move off from dead cold to the top of the blue section.
peranaman
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re-plumbed

Post by peranaman »

Update - put my plumbing back to the way it was form SA originally - and although it's contrary to 'the manual' I've done 140 miles and lost no water.
peranaman
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update and solution

Post by peranaman »

to save me re-typing it all - heres a link to MOCGB

http://www.mocgb.net/forums/showthread. ... -hot/page2
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