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Healey BN6 water pump and overheating problems

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Corolanty

Freshman Member
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I have had consistent overheating with my BN6 since I bought it. On a hot day 24 degrees C plus and in slow traffic (or prolonged idle) the car heats up to over 195 degrees F plus. I have replaced the old original radiator with a new modern core from AH spares and also fitted an electric Kenlowe fan which has improved the situation but not resolved it completely.

I checked all the other usual suspects of fan blade fitting, ignition timing and carb mixture but all seems fine In desperation I removed the water pump and found what I consider a fairly "large" (by impellor standards) gap between the impellor vane and the body (1.5 mm) as the attached photograph shows. The AH workshop manual does not provide any detail on what the gap should (although for the later AH 3000 pump they advise a gap of 0.5-0.6 mm which is what I would have thought the correct gap to prevent recirculation of water around the pump and ensure efficient pumping.

Before I strip the pump and cost to replace bearings and seals I wondered if other members could advise on their experience with BN6/4 pump impellor vane clearances and if my pump is correctly fitted or requires to be stripped and refitted to a closer clearance (if that is possible)?

Many thanks AH BN6 water pump impellor.jpg
 
I have a rebuilt pump on the shelf. Just measured that clearance at .025".

You might also consider back-flushing your block.
BlockFlushSetup.jpg


Also try this: remove the thermostat housing and thermostat, run the engine to operating themp and check your temp gauge against one or two cooking thermometers which can be inserted near the temp pickup. When I did this, my gauge originally displayed around 20 degrees too hot.
 
Corolanty said:
I have had consistent overheating with my BN6 since I bought it. On a hot day 24 degrees C plus and in slow traffic (or prolonged idle) the car heats up to over 195 degrees F plus. I have replaced the old original radiator with a new modern core from AH spares and also fitted an electric Kenlowe fan which has improved the situation but not resolved it completely.

These cars operated on the edge when new. 195 degrees is not overheating, as water without anything else mixed in boils at 212F. If your car stays below 200F in traffic or at idle on a warmish day I'd say your cooling system is operating quite nicely. If you're not boiling the coolant, relax and enjoy the drive.
Click to expand...
 
Corolanty said:
... These cars operated on the edge when new. 195 degrees is not overheating, as water without anything else mixed in boils at 212F. If your car stays below 200F in traffic or at idle on a warmish day I'd say your cooling system is operating quite nicely. If you're not boiling the coolant, relax and enjoy the drive.
Click to expand...

+1. Also, 190degF is supposedly the optimum temperature for engine operation anyway.

I've done 'all the right things' to my BJ8's cooling system--block boiled, Excel core, Texas Cooler, etc.--and it will actually run below the thermostat set point--180degF-at cruise on cool or warm days, then go up to 200+ at prolonged idle on a warm or hot day. I've quit worrying. The problem appears to be that hot air is more-or-less trapped in the engine bay and, without an enclosing shroud, the fan cycles hot air back through the radiator. Louvers and/or side vents would presumably help, as would a good shroud around the fan, but why bother.
 
Just an observation but if all impellor are the same thickness then closing the clearance to the pump body face will increase it to the block recess. Not sure if this makes any odds to operation. For other cars one can have new impellor made from solid alloy with tighter clearance and more vanes to replace the cast iron ones. There is a school of thought that says these can circulate water too fast for efficient heat transfer.
I agree your car is not too hot ...wise to check gauge accuracy too though.
 
Bob_Spidell said:
+1. Also, 190degF is supposedly the optimum temperature for engine operation anyway.

I've done 'all the right things' to my BJ8's cooling system--block boiled, Excel core, Texas Cooler, etc.--and it will actually run below the thermostat set point--180degF-at cruise on cool or warm days, then go up to 200+ at prolonged idle on a warm or hot day. I've quit worrying. The problem appears to be that hot air is more-or-less trapped in the engine bay and, without an enclosing shroud, the fan cycles hot air back through the radiator. Louvers and/or side vents would presumably help, as would a good shroud around the fan, but why bother.
Click to expand...

I was under my car the other day and it looks like it would be pretty simple to fabricate a piece of steel or aluminum to go between the chassis rails to force most of the air coming in through the grille to go through the radiator instead of going under it. Is this a common modification and does it make a difference?

Thanks.
 
Jack T said:
I was under my car the other day and it looks like it would be pretty simple to fabricate a piece of steel or aluminum to go between the chassis rails to force most of the air coming in through the grille to go through the radiator instead of going under it. Is this a common modification and does it make a difference?

Thanks.
Click to expand...


See:
https://www.pbase.com/stevegerow/healeyaircontrol
 
Hi Steve

Thanks for the advice. Still getting use to this high running temp at idle (goes over 200 F some time) but take your point as it seems common with Healey's. I think I will strip the pump anyway and see if I can get a closer gap.

The temperature probe is a new one and when I tested against a lab thermometer before going in it was accurate.

Regards

Brian Webb
 
Hi Bob

That makes sense. Maybe a louvered bonnet is the answer or maybe just accept as it is. Just one of the quirks of a Healey.

Regards

Brian Webb
 
Hi Steve

This could be the answer to traffic temperature although if you are purist it would go against the grain.

Regards

Brian
 
Hi Brian,

The traffic condition is often an issue as the air heated when drawn through the radiator hits the engine and is deflected. Since the car is stopped or moving very slowly, much of this warmed air finds an easier escape moving forward around the steering box and is drawn forward and again through the radiator. New air drawn from the outside is mixed with this heated recirculated air to progressively diminish the cooling effects of the air passing through the radiator and you see the temperature rise. This condition is eliminated if such additional openings as fender vents or bonnet louvers have been implemented. However, there are things that can be done to help mitigate this condition.

The Healey has a porous radiator bulkhead, no fan shroud, and, if you are not using a sleeved thermostat, will allow almost 25% of your coolant to bypass your radiator altogether.

The guys have covered most of the bases and given you some definite things to consider. A while back, I decided to collect a number of simple fixes that could be done by most everyone. The fixes would be as inconspicuous as possible, effective, and for most, inexpensive or even cashless. I have posted this article a few times in response to similar Heat problems "I always wanted a COOL Car" (https://drive.google.com/file/d/0Bx4EjcJmfaScY0NLdlB0YjEwRFE/view?usp=sharing) ... it may give you some further thoughts.

Ray(64BJ8P1)
 
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