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edward
07-05-10, 03:11 PM
Hello all you p heads out there try this problem for size.Last year i finally put the gd on the road it has a rebuilt sbf 302 in it bolted to a 3 speed c6 auto box,i ran it locally through the summer only put 700 miles on the clock & towards the end it was getting hot in traffic,at the time the water was running through a single row aluminium radiator with a built in tranny cooler.Over winter,end of september to march i have fitted an oil cooler & a new four row radiator with t cooler & a 14"electric fan working through a stat with a probe in the top hose.When i put it on the road last month to try it it is still getting hot eg 110/120 degrees within 5 miles and it's not warm out yet,so i took the stat out no change,removed the c heads looking for blown gaskets,cracks in bores no visible signs,then i checked the w pump even though it was new when fitted no problems there.I know it sounds like a water flow problem but the pump is as new,any suggestions,comments before i pull the motor out,regards,Edward.

dolphinboy400
07-05-10, 03:15 PM
air lock sounds like a possibility. are you sure you are getting flow through the block?

Neil O
07-05-10, 04:12 PM
Yup, air lock.

Try installing some kind of valve (radiator air bleed valve) as the highest point in your system and bleed the air out with it stood still and then with it running.

wilf
07-05-10, 05:29 PM
Is your water pump the correct rotation? For a normal v drive you need clockwise, for a serpentine belt drive, ccw. And the 302 had either. Get the wrong one and you get the symptoms you desribe.

Also - check that the bottom hose is not collapsing under the suction from the pump.

Purple AK
07-05-10, 07:33 PM
Hello all you p heads out there try this problem for size.Last year i finally put the gd on the road it has a rebuilt sbf 302 in it bolted to a 3 speed c6 auto box,i ran it locally through the summer only put 700 miles on the clock & towards the end it was getting hot in traffic,at the time the water was running through a single row aluminium radiator with a built in tranny cooler.Over winter,end of september to march i have fitted an oil cooler & a new four row radiator with t cooler & a 14"electric fan working through a stat with a probe in the top hose.When i put it on the road last month to try it it is still getting hot eg 110/120 degrees within 5 miles and it's not warm out yet,so i took the stat out no change,removed the c heads looking for blown gaskets,cracks in bores no visible signs,then i checked the w pump even though it was new when fitted no problems there.I know it sounds like a water flow problem but the pump is as new,any suggestions,comments before i pull the motor out,regards,Edward.
Back to square one! Before you disassemble/throw any more money at it! Have you actually checked the accuracy of the gauge? They have been known to lie :rolleyes: ;) Is it actually puking water?

Happy Jim
07-05-10, 10:43 PM
Maplins do a pocket infra red temp gauge for about a tenner which will tell you whether it's really hot or you've just got buggered sender/guage (or mismatch of sender/guage). Got to be a better path than engine removal.

Rgds

Jim

edward
08-05-10, 07:48 PM
I have 2 means of checking temp,dial on dash,thermostat in engine bay controlling the fan,when the gauge on the dash reads 110 the dial in the engine bay when rotated is 110,they can't both be lying to me,regards.

Purple AK
08-05-10, 08:02 PM
I have 2 means of checking temp,dial on dash,thermostat in engine bay controlling the fan,when the gauge on the dash reads 110 the dial in the engine bay when rotated is 110,they can't both be lying to me,regards.
What happens if you set the Fan Stat at 90 degrees?

edward
08-05-10, 08:14 PM
What happens if you set the Fan Stat at 90 degrees?
fan stops on constantly,temp still rises 110 plus even when on the move,regards.

mike huddart
08-05-10, 08:24 PM
All this talk of rebuilt motors and overheating sets the alarm bells ringing. Sounds like you have checked most things but before you go any further check the head gaskets are both the correct way round. You have to flip one over to get the water passages at the rear and it is a common mistake to get one back to front, had an American import with just your symptoms that the new owner had managed to struggle on with for over a thousand miles. Replaced the head gaskets the correct way and everything fine.
You can check the gaskets in situ, they have a little tab in the bottom corner and if fitted correctly you should be able to see both tabs in the bottom front corner of both heads.
Mike

edward
08-05-10, 08:25 PM
Is your water pump the correct rotation? For a normal v drive you need clockwise, for a serpentine belt drive, ccw. And the 302 had either. Get the wrong one and you get the symptoms you desribe.

Also - check that the bottom hose is not collapsing under the suction from the pump.
v belt c wise,impeller ok,flexi stainless bottom hose,regards.

edward
08-05-10, 08:34 PM
All this talk of rebuilt motors and overheating sets the alarm bells ringing. Sounds like you have checked most things but before you go any further check the head gaskets are both the correct way round. You have to flip one over to get the water passages at the rear and it is a common mistake to get one back to front, had an American import with just your symptoms that the new owner had managed to struggle on with for over a thousand miles. Replaced the head gaskets the correct way and everything fine.
You can check the gaskets in situ, they have a little tab in the bottom corner and if fitted correctly you should be able to see both tabs in the bottom front corner of both heads.
Mike
Hello,felpro gaskets are clearly marked,i have just replaced them after taking the heads off looking for cracks etc.

Vidge
08-05-10, 08:35 PM
Air lock causing a steam pocket to form ?

Try filling the water system through the top hose then running the car with the header tank cap off and top it up frequently. Don't let it get too hot before you put the cap back on the system needs to be pressurised to stop it boiling.

Head gaskets on backwards ?

I think the 302 has holes in the head gaskets at the back of the block to let water through, from the look of the gasket you could mount them the wrong way round. I'm not sure how you could check for this short of pulling the heads off.

Vidge
08-05-10, 08:36 PM
Hello,felpro gaskets are clearly marked,i have just replaced them after taking the heads off looking for cracks etc.

I didn't spot Mike's post :)

edward
08-05-10, 09:00 PM
Air lock causing a steam pocket to form ?

Try filling the water system through the top hose then running the car with the header tank cap off and top it up frequently. Don't let it get too hot before you put the cap back on the system needs to be pressurised to stop it boiling.

Head gaskets on backwards ?

I think the 302 has holes in the head gaskets at the back of the block to let water through, from the look of the gasket you could mount them the wrong way round. I'm not sure how you could check for this short of pulling the heads off.
Hello filled it up through the header tank,run it up topped it up,run it with and without the stat, no difference

Purple AK
08-05-10, 09:06 PM
I guess you've checked the timing?

edward
08-05-10, 09:15 PM
I guess you've checked the timing?
Hello 10 btdc,i checked it the normal way and then with a t light,it advances to 24 degrees when revved,regards.

Vidge
08-05-10, 09:22 PM
Have you tried disconnecting the tranny from the cooling system ? You might be diagnosing the wrong component here.

edward
08-05-10, 09:46 PM
Have you tried disconnecting the tranny from the cooling system ? You might be diagnosing the wrong component here.
Hello, i have a deep aftermarket pan on the trans which holds approx 3 to 4 pints extra which helps to cool it,i had thought of trans drag but it goes up and down the gears ok and the pipes to the cooler don't get abnormally hot.Also i have an engine oil cooler fitted,regards.

Purple AK
08-05-10, 10:57 PM
Hello 10 btdc,i checked it the normal way and then with a t light,it advances to 24 degrees when revved,regards.Ahh. You really need to be looking for 32-34 degrees all up. Try setting it to 18 degrees static and see what happens ;)