Firstly, thank you to all forum members for posting such great advice. As a new Sprint owner this has been so valuable to understanding the car.
My aim is to get confident enough with the Sprint to get some miles in over the coming years and the only thing that makes me nervous at the moment is the cooling.
I am based in Greenwich, South East London, taking the car out every other day. Even with a cooler ambient temperature and at idle with the bonnet off, the following happens:
Takes 5-10 mins to get up to temperature
Stabilises at around 90C, only going below when moving
The fan does not appear to bring the temperature down, only hold it at 90C
After stopping 5 mins, it will creep up to 95C
Sitting in traffic for 15 mins it will get close to 100C
With the bonnet off and left for 15-20 mins it will start to get to 100C without moving
Here is a summary of what has been done so far to improve the situation:
The engine was stripped and put together again in May. It appears to be running well with no leaks or other niggles.
I have fitted a Coolex ‘fatboy’ radiator and the associated fan in place of the original radiator and Kenlowe fan. It has been bleed with the radiator cap open with the car lifted at the front with new antifreeze for 10 minutes, squeezing the pipes to remove any air. The expansion bottle appears to be working.
The thermostat has been replaced with a new 82C version which was tested and is working.
Working on the carbs with a Carbtune and Colortune shows the carbs are balanced as best as I can manage and the flame at the spark plugs is blue on idle.
There is an electric ignition.
Here are some areas I am working on:
There is an MGB oil cooler near the front of the engine bay. The thermostat (a Mocal OT/1 1/2" Remote Thermostat) does not appear to be opening, so the oil is coming out of the filter and back in without being diverted to the oil cooler.
The oil pressure is 60psi when driving but I can’t work out whether there is an uprated pump or something else happening.
I have in my possession the correct air deflection piece for the bottom of the radiator and the bonnet foam but have not fitted this yet. The engine heats up more than I would like with the bonnet off so I suspect this won’t be a game changer.
Am I being realistic about having a car that will hold below 90C in traffic in 20C sunshine? Any advise would be greatly appreciated.
May I suggest that you check the thermostat again, this time in boiling water and a thermometer, as I wonder if the new therostat is opening at the correct temperature. I cannot recall from memory the different thermostats recomended by Lotus, but it may be that a lower temp stat may give an improvement.
To simplify matters, ignore for the time being about the oil cooler as most Elan’s do not have one fitted, yet run at a satisfactory water temperature. Are you taking the temperatures off the instrument gauge, as this in itself could be giving a false reading. You can check this by using one of those temperature reading guns that are available. Point the gun at the area around the water pump (as the impeller on the pump may not be pushing enough water if it is badly corroded), at the radiator top and bottom (there should be a reasonable temp drop between top and bottom of the rad core). Also a reading around the thermostat housing and at various random points around the engine. Look for areas that are significantly different around the block, the head etc. Finally compare the readings with those on the temperature gauge which may show if the gauge is not accurate and I assume the timing is correct, as this too can make the engine run hot if it is too far out of adjustment.
My Elan is an early S4 which is cooled with the S3 type wide radiator and a mechanical fan. I have never had any particular issues with overheating in traffic in over 30 years of use. I have a mate with an early Plus 2, again with a wide radiator and mechanical fan, no overheating problems.
I agree with all the points Tony has made, but my observation, for what it is worth, is that most complaints of overheating seem to be from owners of later Elans with the narrow radiator and electric fan. You have addressed the radiator size, at least to some extent, by fitting an uprated type, so if it was me, and I could find no other issues, I would try fitting a mechanical fan on the water pump pulley, and see if this improves the situation. Either use a proper twincam fan, or find something from a 60s or 70s Ford that will fit. If there is no improvement, it can easily be removed.
The other points you mention:
For road use you don’t really need an oil cooler, so its operation is unlikely to make much difference.
The standard oil pump gives 40 psi, so your car must have an uprated pump. Again, it will make no difference to the overheating issue.
It is worth fitting the deflector plate and foam, the more air that passes through the rad, rather than around it, the better it will work.
Here’s another perspective. If the system is operating well under boil over, you have no problem to address. Boil over with a std rad cap is well over 100 deg c, so drive the car and worry about something else.
If you absolutely have to mess with it, figure out how to add air flow through the rad when the car isn’t moving. A larger capacity electric fan, possibly. Or adding a mechanical fan, or another electric fan on the ‘pull’ side.
Are those last bullets all with the engine running? Is the electric fan running at that time? The fan coming on at 90C doesn’t seem unreasonable, but temperatures going above that level after a few minutes – even with the fan running – does not make sense. I would examine the fan operation, including simple stuff such as ensuring it is spinning in the correct direction to move air through the radiator.
Another possibility I believe was already mentioned, that being the water pump not moving sufficient fluid to get the maximum effectiveness out of the radiator &c.
Welcome from a fellow Sprint owner. Cooling a Sprint is a very well covered topic on this forum. My recommendation is always fit the earlier S3 full width radiator. The original small width radiator tends to only just be sufficient and does not take much to overheat. Fitting the deeper Fatboy radiator can help but if you put a modern fan onto the front it blocks a lot of flow and may well undo the advantage of a deeper core. I have a full width S3 radiator with a dense 2 core matrix and it never gets hot even in the hottest of weathers. In stationary traffic the temp obviously rises but the fans kick in and it drops quickly.
A couple of things to try with a small radiator if its overheating when driving along . Fit the cardboard deflector under the radiator and the foam on the bonnet . You should already have two holes cut in the inner wing by the exhaust manifold usually covered with a piece of mesh. The top hose can trap air and the filler cap is not necessarily the highest point so you might want to raise the front end when bleeding the air. Check the top hose orientation, you want it dipping down or running horizontal. If it curves upwards it can trap air. Thermostats, use one with the small bleed hole and “jiggle pin” so air does not get trapped underneath it. (I had a batch made specially of 72 and 78C so let me know if you want one). Another point that is often overlooked. The heater hoses come straight out the top of the matrix behind the dash so can be the highest point in the system especially if people use long curves to avoid kinks. Try to keep the hoses as low as possible and bleed system with the heater open.
If you do all of this and it still overheats then the system is not up to it and you need a bigger radiator “Welcome to Sprint ownership” . The S3 rad slots straight in on the existing mounting points. The only issue might be it catches the bodywork on the bottom lip where it turns back under. Mine did but its a minor job, 5 minutes of fettling and it slotted in nicely.
Thank you Tony, I had not thought about doing an investigation like that, and as luck would have it I have a heat camera so I will post my results when i’m next under the bonnet
Thanks Steve, I guess the big question is at what temperature should I be worrying about damage? I’ve had it to 105C briefly in traffic before pulling over and letting the engine cool, am I being over cautious?
Hi. Yes the fan is on and is blowing in the correct direction. The water pump was replaced in May and is pushing water round but it’s hard to tell the flow rate.
Thanks Mark, I do have a 74C thermostat which I will try at some point to see what the difference is. I will also try the Kenlowe fan again which is further back to see if that is moving more air
Thank you for the detailed write up. In hindsight I wish I had put in an S3 radiator, but I i will try the Kenlowe fan to see if that makes a difference as I suspect the fan is not doing it’s job how I have the engine bay configured currently
I have a Thermostat with the jiggle pin from Kelvedon motors. I have a 74 degree version I will also try, thank you for the offer of other versions.
I shall look at the heater hoses as it didn’t cross my mind at all, thank you.
A quick question, what are the max temperatures are you seeing from your setup?
Bruce, with a standard 10psi rad cap, the boiling point of the water will be approx 112 degrees C. With antifreeze, it will be higher. I couldn’t see it mentioned above, but the Smiths thermometer is not a precision instrument, so I wouldn’t really rely on it at all to give an accurate temperature indication.
In principle, you are not going to do any damage to the engine as long as the water doesn’t boil away. Generally a colder engine performs better, but if the temp is too low then the combustion products which accumulate in the oil don’t get evaporated and the oil becomes contaminated. Somewhere around 80 to 90 degrees seems to be a compromise that manufacturers choose.
I wouldn’t fit a mechanical fan - its the worst of all worlds, its a waste of power when the car is moving, and not big enough when the car is stationary. The Sprint rad is always considered marginal, I have fitted a larger one to my Sprint and dont have cooling problems.
Edit: Just add to the points above, the oil cooler is a waste of time unless you plan on track days or similar. It won’t contribute to cooling when the car is stationary as very little air goes through unless the car is moving..
Another couple of points, first what pressure cap is fitted to the radiator. There is much talk about the various fans, either mechanical or electrical, but I have to agree that the mechanical fan is marginal, also why did Lotus go over to an electric fan during later production, presumably to deal with the mechanical fan not being up to the job.
My car spent its life in South Africa where the ambient temps were higher, to get round this the PO fitted a larger electric fan, but kept the small radiator and used the car in competition events with this set up without problems. Whilst changing my wiring harness in the front I incorporated a switch and relay into the fan system, this kicks in automatically or can be switched on to run permanently if required.
If I recall correctly Phil Harrison wrote a submission together wuth a wiring diagram on this forum, a little while back. So I would look to your electric fan again and check its width across the rad to make sure it is large enough for your engine. Also does it have a rheostat switch so you can set it to a temperature that suits your driving conditions. As to a suitable running temperature you should be around 80/85 degrees, which allows a margin when in heavy traffic.
As I said previously a temp reader would be my first port of call to verify that the readings on your dash gauge are consistent with those around the engine, as you may be chasing a red herring if the gauge is inaccurate
With a 10 psi cap and a 50/50 anti freeze mix the boiling point is 123 deg c. So you’d want the system to stabilize below that.
If your Sprint is like mine, there’s no issue when the car is moving. The issue is at idle and/or stop and go traffic. What I did was put on a higher capacity radiator (26R) version, which didn’t solve the problem, and then a higher capacity fan, which did. At least in an Oklahoma summer, with 105 degrees F ambient temps.
I also put in an override switch to start the fan when I know I’m going to need it. So far the system stabilizes at 95 deg C or so.
Thanks Andy, a great point on the oil cooler. I will keep playing around, I think the fan is the weakest part of the system at the moment, but my investigations may show otherwise
I am in Hong Kong where it is usually hot and traffic is often thick and slow [stop that!]. My S4/Sprint also has a rebuilt engine and a fatboy Coolex radiator with their 2 SPAL fans blowing through it, thermo set to 92 degrees.. Ambients being what they are, I run with no thermostat at all.
All the advice above is good but the cooling remained a problem until I also disconnected the belt to the standard water pump and fitted an electric water pump from Davies Craig in Australia Davies Craig Electric Water Pumps (EWP) Information . That cuts in around 82 deg, shown on the LED its control panel under the bonnet but some people mount them in the glovebox, and learned to stop looking at the gauge [changed at least once on the way].
Bingo. We found the gauge reads about 8 to 10 deg high. The pump generally does the job and the fans cut in momentarily in the hottest conditions. It would have been even better had I taken out the impeller in the existing water pump but my mechanic is not a double-jointed dwarf and I didn’t want the engine out again.