Highway overheat

[DerekJ]

My car does not overheat when stopped at a traffic light. if a car does that it has a problem. Thermostats don't solve overheating problems. its not what they are for.

 

[Keoke]

Just try this as presented by: Brinkerhoff

And i think you will be OK

BTW I run a Texas cooler style fan from Moss, a std. radiator that's been recored, and a 160 degree thermostat. I stay under 175 degrees in the summer





This is a well tested solution.

 

[Bob_Spidell]

Here's an oddity: both my BJ8 and BN2 often run cooler than the thermostat set point at highway speeds. Every other car I've owned will warm up to the thermostat rating, then level off. The Healeys will run below the 180deg thermostat set points on all but the warmest days, and they'll go over the set point if I have to sit at idle for more than a couple minutes (both temp gauges have been rebuilt and calibrated). I can't explain this, unless the engines are able to dissipate enough heat without coolant flow through the radiator, but then why do they get warmer sitting at idle? I've tried several thermostats, and checked them against thermometers. The BJ8 has a 180deg Robertshaw with a BCS sleeve soldered to it, but the BN2 has a plain ol' 180deg Stant.

On another note, I don't think it's good for any engine to run too cool; I've read 190deg coolant temp is ideal--I think 'modern' cars usually run 190-200deg--but I prefer having the 10deg margin.

 

[Keith_M]

My car does not overheat when stopped at a traffic light. if a car does that it has a problem. Thermostats don't solve overheating problems. its not what they are for.

I agree that thermostats don't help with overheating, but the bypass that Ray mentioned can be important. As for traffic lights, I think many of us living in warm climates (Utah is pretty warm in the summer) have trouble with the engine temp going up when stopped in traffic. For me, it's particularly bad if I've been cruising at high speed for a while and then abruptly stop for a traffic light. My engine temperature usually climbs over 200 fairly quickly in that situation. It drops quickly once I get moving again. From what I have heard from others, this is fairly common. Overheating at high speeds seems less common.

 

[Keith_M]

Here's an oddity: both my BJ8 and BN2 often run cooler than the thermostat set point at highway speeds. Every other car I've owned will warm up to the thermostat rating, then level off. The Healeys will run below the 180deg thermostat set points on all but the warmest days, and they'll go over the set point if I have to sit at idle for more than a couple minutes (both temp gauges have been rebuilt and calibrated). I can't explain this, unless the engines are able to dissipate enough heat without coolant flow through the radiator, but then why do they get warmer sitting at idle? I've tried several thermostats, and checked them against thermometers. The BJ8 has a 180deg Robertshaw with a BCS sleeve soldered to it, but the BN2 has a plain ol' 180deg Stant.

On another note, I don't think it's good for any engine to run too cool; I've read 190deg coolant temp is ideal--I think 'modern' cars usually run 190-200deg--but I prefer having the 10deg margin.

The only reason I can think of would be a sticking thermostat, but since you've tried several that doesn't sound like it. Its hard to believe the huge lump of iron under the hood of a Healey could dissipate that much heat without coolant flow. I have heard that running too cool is bad for the engine, and I think some modern engines run even hotter than the range you gave.

 

[Bob_Spidell]

...Its hard to believe the huge lump of iron under the hood of a Healey could dissipate that much heat without coolant flow...

I can't believe it either, but that's what two calibrated gauges and several thermostats are telling me. I'm fine with it.

 

[DavidThorn]

Perhaps I may have missed it somewhere in this thread but has the temperature gauge been checked. The easiest way seems to be via a food temp probe into the top of the rad and compare the temp it shows to what the gauge is showing.
Best not to mention this to whoever does the cooking in the house.
The usual care when removing a hot radiator cap of course

 

[Patrick67BJ8]

Here's an oddity: both my BJ8 and BN2 often run cooler than the thermostat set point at highway speeds. Every other car I've owned will warm up to the thermostat rating, then level off. The Healeys will run below the 180deg thermostat set points on all but the warmest days, and they'll go over the set point if I have to sit at idle for more than a couple minutes (both temp gauges have been rebuilt and calibrated). I can't explain this, unless the engines are able to dissipate enough heat without coolant flow through the radiator, but then why do they get warmer sitting at idle? I've tried several thermostats, and checked them against thermometers. The BJ8 has a 180deg Robertshaw with a BCS sleeve soldered to it, but the BN2 has a plain ol' 180deg Stant.

On another note, I don't think it's good for any engine to run too cool; I've read 190deg coolant temp is ideal--I think 'modern' cars usually run 190-200deg--but I prefer having the 10deg margin.[/QUOTE
]I wonder if the hotter running temp at idle is because the air under the hood is forced outwards to the front of the car and then rerouted back through the radiator? The Healeys do not have anything that really "masks off" the sides of the radiator and the wheel wells.

 

[Frameman]

The engine has to breathe. If your exhaust is plugged or restricted your engine cannot get rid of the burnt gases and will cause your engine to overheat. Disconnect the two front pipes at the front mufflers, take the car for a drive and see if that makes a difference. A plugged exhaust system is as inefficient as a plugged radiator. The exhaust system in an Austin Healey is very restrictive. I do understand the need for back pressure but the Healey exhaust system is excessive in that area.
Marty

 

[steveg]

I just spent the last hour and a half pouring through all the posts about overheating. There where a few that had the same problem I have, overheating at highway speeds (210-220). I have a rebuilt engine and recored radiator. I took out the belt driven fan and put in an elecric pusher fan that turns on at 190 degrees. It does a fine job of keeping the temps at 190 degrees until the speed is above 50 MPH. I recently put in a thermostadt blanking sleeve to improve water flow, but it did not help. I read a few posts that reported problems with replacement water pump castings, not sure if this could be an issue. I hate to fix or replace things that aren't broke, any ideas where to begin? I have a 67 BJ8. Thanks for your help, Steve

Seems like the easiest thing to do would be to temporarily remove the electric fan and drive the car over 50 mph. If you still have the problem, you've eliminated the fan as a possibility. If the problem goes away, proceed according to previous suggestions for either returning to stock or relocating fan.

 

[steveg]

Here's an oddity: both my BJ8 and BN2 often run cooler than the thermostat set point at highway speeds. Every other car I've owned will warm up to the thermostat rating, then level off. The Healeys will run below the 180deg thermostat set points on all but the warmest days, and they'll go over the set point if I have to sit at idle for more than a couple minutes (both temp gauges have been rebuilt and calibrated). I can't explain this, unless the engines are able to dissipate enough heat without coolant flow through the radiator, but then why do they get warmer sitting at idle? I've tried several thermostats, and checked them against thermometers. The BJ8 has a 180deg Robertshaw with a BCS sleeve soldered to it, but the BN2 has a plain ol' 180deg Stant.

On another note, I don't think it's good for any engine to run too cool; I've read 190deg coolant temp is ideal--I think 'modern' cars usually run 190-200deg--but I prefer having the 10deg margin.

They get warmer sitting at idle because the cooling system is marginal. Even with my extensive baffling, my car gets warmer when idling. Remember that paper previously linked to where the Tiger guys went to great lengths to modify the car so it would idle indefinitely in a parade without overheating. Healeys getting hotter while standing still is normal in warmer climes. As previously mentioned, recirculating hot air is probably the culprit.

IIRC when I tested my Robertshaw thermo, it started opening a few degrees below 180. IMHO the car cooling itself without coolant flow through the radiator is the least likely possibility. The thermostat is probably opening and closing to let coolant through.

Just my 2 cents.

 

[Patrick67BJ8]

The engine has to breathe. If your exhaust is plugged or restricted your engine cannot get rid of the burnt gases and will cause your engine to overheat. Disconnect the two front pipes at the front mufflers, take the car for a drive and see if that makes a difference. A plugged exhaust system is as inefficient as a plugged radiator. The exhaust system in an Austin Healey is very restrictive. I do understand the need for back pressure but the Healey exhaust system is excessive in that area.
Marty

One good thing I did to my exhaust manifolds was to have them sandblasted on the insides before I had them "coated". I read about doing that about 20/30 years ago in a Tech Tip for performance cars.

 

[SideShifter Tri-Carb]

I once had a MB 450SL that I replaced the water pump with an aftermarket one. After installing it, the car ran fine at city road speeds and stop lights. When I took it on the highway at 70 mph, it ran much hotter than previously. Long story, short, I found out that the clearance with the impeller to the pump body was much greater on the aftermarket one. The gap was noticeably different when compared side by side. Replaced with MB part and problem was solved.

After researching further, the consensuses was that the pump would cavitate and become inefficient in flow at higher speeds. Cavitation becomes worse as the temperature of the fluid approaches its boiling point. As the car ran slower, less heat was generated and the flow was enough to bring the temperature away from the boiling point, thus eliminating the cavitation.

 

[Lotuswins]

Steve,

I just thought of a couple of other things that may be going on:

1) Check if your lower radiator hose is collapsing at higher rpm's? Though not common with LBC's generally due to smaller diameter hoses, it is a common issue with larger V8's. Apparently the suction of the pump is so great that if the hose hasn't the wall strength then the atmospheric pressure will collapse it, restricting flow such that the motor will overheat. New hose or a large wire coil will fix this issue.
2) Have you tried the scavanging plate under the frame as described on the Healey6 website? (can't remember the website address). Basically a flat sheet metal panel between the frame rails from the front cross member backwards to the middle of the oil pan or so? You could fashion one up out of card board and duct tape it into place to check its effectiveness.

 

[BlueHealey1951]

Been away on vacation, Thought I would check to see if there were any new suggestions. You brought up an interesting point. When I rebuilt the engine, I noticed a significant difference in impellers between the replacement water pump and the original. Since I plan on taking the radiator out, any suggestions on where to buy a new pump?

 

[Bob_Spidell]

Been away on vacation, Thought I would check to see if there were any new suggestions. You brought up an interesting point. When I rebuilt the engine, I noticed a significant difference in impellers between the replacement water pump and the original. Since I plan on taking the radiator out, any suggestions on where to buy a new pump?

Sorry, AFAIK all the new ones are County brand and they suck. If you have an original, you're better off getting it rebuilt. Michael Salter rebuilt one for me, but he's been having trouble getting parts:

https://www.netbug.net/blogmichael/

 

[steveg]

Sorry, AFAIK all the new ones are County brand and they suck. If you have an original, you're better off getting it rebuilt. Michael Salter rebuilt one for me, but he's been having trouble getting parts:

https://www.netbug.net/blogmichael/

He just did one for me in the last couple of weeks. He turned it around in a few days.

 

[ttrotter]

+1 re Michael Salter. I bought a rebuild kit from him for my BJ8 PH2 water pump just a few weeks ago. I didn't have a need for it--YET!
Tom
Tom

 

[Lotuswins]

fyi, here is a pic of an original (right) and a re-pop impeller. Note thicker base, and fins not as high. I estimate maybe 2/3 of discharge area in the re-pop. Note that this re-pop had to be from late 70's, not the current vendors.

 

[dcarlg]

I hope you resolved this overheating at speed issue. I had the same problem. After reviewing previous posts and calling British Car Specialists, I developed a successful plan. This included installation of a sleeved thermostat, Texas Cooler fan, BCS fan shroud, recored radiator and new radiator cap. I also placed a slim pusher fan in front of the radiator for stop and go traffic. So far, so good.
It seems that an aftermarket Flex Fan previously placed was not moving air at speed and contributed to overheating.