Overheating Issues

[iansutch]

I took the car out for an initial drive last week - covered some 20 miles on mainly fast B roads. As soon as I got back home and stopped (within a few seconds) the engine overheated - a huge plume of steam off the header cap combined with a split bottom hose and a large amount of coolant dumped all over the drive.

I replaced the bottom hose, filled the car with water only (just in case there were still leaks) and took the car for a quick 5 min spin, again on fast traffic free b roads during which the water temp gauge hit 140 degrees C so immediately returned home. I didn’t notice the fans coming on so immediately switched the manual overide on and let the car cool. Some time after I realised that I had set the cap to only half closed and am wondering if this would have contributed to a higher temp reading?

Later in the day I took out the water thermostat and tested it in boiling water and it opened fine.

One other thing I discovered today is that only one of the fans is working. (2x pacets placed in front of the rad)

I am trying to figure out now what the next logical troubleshooting step would be as there are so many variables with the coolant system:

Leaks - ruled out
faulty thermostat - ruled out
faulty ECT Sensor
faulty fan wiring
Faulty fan
blocked coolant passageways
faulty radiator
faulty water pump

What should I address next?

[Karl]

You just bought the car for a lot of money. My friend was also interested in the car, but it was gone when we wanted to look at it. So with all this problems we were lucky not to get it? Did you ask John Kox about the problems?
What PSI rating is on the cooler cap?Is there an expansion tank fitted? Test the gauge for correct reading, but if the pressure split a hose something is wrong in the system. As long as you are on the move you do not need the cooling fans. When the car is stationary, at what temperature do the fans kick in? Do they stop again? Do all parts of your circuit (cooler, hoses) feel the same temp? Head gasket may bee, if all other things are okay.
Best regards and good luck
Karl

[iansutch]

Hi Karl
I have spoken to John Kox and he said that there have not been any previous overheating issues.

The cap has a 21-25 lbs rating and there is a header tank fitted. The fans do not kick in when stationary, it needs manual overriding, and at present it looks like only 1 fan is operational.
There is a difference in temp in hoses - the top hoses are much much hotter than the bottom hoses but I thought that was to be expected?
Thanks for the response, looks like I have several issues - possible overheating when not stationary, failure of fans to come on when stationary, only one fan operational.

Hi Alan
Thanks for the comment. Do you think this was the likely problem for the initial overheating whilst out on the road or after I had replaced the hose and refilled?

[Karl]

21-25 psi is way too much! You should use 15 psi there, otherwise the hoses get damaged. I was asking if you have a seperate expansion tank (MGB sytem).
I also had a header tank where the full flow of cooling water was going through. Everytime I stopped, the car was dumping water. Now, with the separate tank fitted, I can completly fill the cooling circuit without any air left and the expansion tank takes the difference between the cold or hot cooling circuit.
So, with the car idling, when you switch the fans on at 90 deg,, do they bring the circuit temp. down? When you say your circuit is cooler after the radiator so this is a good sign, but only when you are driving or the fans are operating. When you say the filler cap was only half closed, did you loose water?
Regards
Karl

[iansutch]

I didn't notice the fan reducing the temp too quickly, the water temp was at 140c so I switched the engine off. With the cap half closed there was only a very small release of water.

[Roger King]

Is this the 351W block, John Abel's old car? I would assume John would have had the block properly cleaned out before build, and given the typical use/history of these cars it is unlikely to have already silted up.
In my experience the 289/302 is just on the right side of marginal with the Hawk radiator (which I assume is what you have), so the larger 351W block, and the corresponding lack of space for cooling air around it, will not encourage cool running.
Check for head gasket, although I think this unlikely if the car is running fine. Any mayo in the oil filler cap or on the dipstick? I would think the cap pressure is high - you should be able to drop it to, say, 13lbs, but I run zero pressure with Evans in my Mustang (also 351W block stroked to 393) with no problems. I do, however, have a reasonably large overflow tank (as Karl was suggesting) which allows for expansion and suck-back on cooling.
I would think it's a combination of only one fan running (my 289 Hawk fans ran a lot of the time) and the marginal nature of the system, especially with the slightly bigger engine. Get both fans working on a thermostatic switch positioned on the rad tank, and make sure the radiator is properly shrouded so no air can get around the sides. Another issue, which may or may not be apocryphal, is collapse of the bottom hose at decent revs due to the suction effect of the water pump. Gerry designs in stainless sections for this, so if you have that it shouldn't happen. If you have a long length of rubber hose without internal wiring (a 'spring'), it's a distinct possibility and would happen at cruising speed as you suggest, so try replacing with rigid tube and just use a short rubber connector at each end.

edit - Gerry's copper radiator has a threaded boss for a thermo switch on the RHS tank - these are standard TR6-type, available from Moss. As I said mine used to run more often than not so I would not rely on manual switching. And both must work - one side of the rad will be significantly cooler than the other as it's a crossflow rad, and it may be the important one that has failed.

[catsx11]

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[clive]

The best way I've found to fill the coolant system is to remove the top heater hose where it enters the bulkhead and using a small funnel, fill the system through there, holding the hose as high as you can until the fluid comes out of the heater.

[Roger King]

The best way I've found to fill the coolant system is to remove the top heater hose where it enters the bulkhead and using a small funnel, fill the system through there, holding the hose as high as you can until the fluid comes out of the heater.

You shouldn't need to do this with a Ford engine if the thermostat has been fitted correctly as it should have a small bleed hole in the thermostat backplate. If it hasn't, I would drill a 1/8" - 3/16" hole just in from the rim and ensue it is fitted at the top when replacing the thermostat. Airlocks are unlikely, and why would it develop one now? Had the system been drained and refilled before the first problem?
Top hose should be pretty hot, bottom hose noticeably cooler. I would keep checking the level as the coolant will find its own way round in time.
Sounds to me like a sticking thermostat, maybe behaving differently under road conditions - very cheap to change as a test. SBFs were designed to work on 195° thermostats, you could go down to 180°but no lower. The thermostat does not control the temp the engine runs at, it controls the temp the radiator comes into circuit, so lowering the thermo temp will likely make no difference from that point of view.
Get the fans and fan switch sorted first.
Roger

A further thought, a long shot: it's not had a new water pump recently, has it? Ford water pumps come in two different rotations, and if by any chance it's had the wrong one fitted...

[iansutch]

Hi Roger
Yes its a 351W block in Johns first Hawk. The engine has only done 8500 miles in 12 years so little used overall. Both the oil filler cap and dipstick are clean so don’t think its the head gasket.
Regarding the bottom hose and the suction effect of the pump - I think thats a very pertinent point. There is a short section of rigid tube but the hose that split was of poor quality and did not have internal wiring so I think thats a distinct possibility. One thing I haven’t been able to deduce is if the hose split first or the radiator cap blew first.

I will get the fans and fan switch sorted next and report back. Many thanks for your comments.