radiator shroud
 

Is anybody running a radiator shroud to help the fan pull the air through the radiator ? Summers here are hot and last year the car would get very hot creeping along in slow traffic or idling for any length of time.

If you are, did you fab it up yourself or find something that was a good fit ?
Thanks
Greg

Won’t work you will have less air flow and distribution, closing it in and even worse in a hot climate

Answer is to service , flush your cooling system and fit a five bladed fan much better results with some simple maintenance even will drastically improve also fit the right / correct thermostat rating as that will open soon ideally 76-80 degrees 76 is perfect 👌

Hope that helps

Kind regards
Robert.w

A radiator fan shroud on a puller fan configuration can help a little bit. A puller fan tends to concentrate air flow through the section of the rad directly in front of the fan. A shroud helps to force air flow over a larger area of the radiator which can improve things slightly.

It is normal for the temperature to rise when the car is stopped and drop as the car starts to move forward. Normally, the dead band in the original temperature gauge hides this fluctuation. If the temperature gauge is moving into the red zone on hot days when stopped, my first suggestion would be to check the rad. On my 142 (which has a horizontal tube radiator) I had some hot day / running hot problems. I installed a large electric rad fan in push mode and this did not resolve the problem. A little further investigation with my hand showed that the lower one third of the radiator tubes were completely blocked about mid way across the radiator. I could place my hand on the tubes near the left tank (inlet) and they were hot and as I ran my hand along the tubes I could feel a very definite temperature transition at the mid point and the tubes ends near the outlet tank were just a bit above ambient temperature. This came as a surprise as a couple of years earlier I had removed the rad and had it cleaned at a rad shop. I think they just cleaned the outside and sprayed it with a new coat of paint. This time I took the rad to a different shop and they tanked the rad in caustic and then did a flow test and tube temperature check to insure that all tubes were flowing. That fixed the problem.

Home flushing a cooling system does not really cut it. Unless you have already done this, I recommend that you remove the rad and have it caustic cleaned and then flow checked. If you can, ask around to try and find out who is good and who isn't. Of course, that doesn't always work out because the first shop I used came recommended and I picked the second shop on the basis that they were not the first shop. The correct 'indicator' is probably that the first shop is no longer in business and the second shop is till in business - hindsight is 100%.

If the running hot problem persists with a clean rad, I would not bother with a shroud and just jump to a thermostatically controlled electric fan. The electric fan has the great advantage that it is not engine speed dependent so you continue to get maximum air flow even when the engine is idling.

One of the better descalers for these and mixed metals compatibility is central heating system cleaner:~

Leave as long as possible whilst bringing the engine up to temperature a few times- then flush out- you may just discover tomato soup.
Bob.

When I measure the temperature (infrared thermometer gun) across the face of the radiator it is warmer at the top than the bottom. The hottest spots are either upper corner. The temperature drops from the edges in towards the middle across the entire radiator.

Looking at the airflow (tuft of yarn), in front of the radiator the upper corners are dead spots. On the engine side, the air is moving out away from the fan at the upper corners.

This leads me to think that the radiator is okay and a lot less cooling is taking place where the fan isn't.

Warmer at the top and cooler at the bottom is the way it should be. If there are tubes that are plugged I would expect them to be quite noticeable with a temperature sensor or IR camera.

The shroud mounted around a puller fan will help distribute air flow over more of the radiator surface (those corners) which will help improve cooling when the car is stationary / moving slowly. Whether it will help enough is an unknown. Given the work associated with trying to fabricate and securely mount a shroud, I personally would be inclined to add an electric pusher fan because I expect that a pusher fan installation will be less effort than a sanitary shroud installation. I picked up a mungo sized pusher fan for my 140, the largest that I could fit in the cowl area in front of the rad from Speedway Motors for less than $80 (granted that was about 7 years ago) and I run without the OEM fan. I have an aftermarket coolant temperature gauge with no dead band and you can see the coolant temperature start dropping approximately 1 minute after you hear the fan start up.

That said, if you are still using a generator a big electric fan may not be the hot ticket (no pun intended). My pusher draws about 10 amps. The original 35 amp Bosch alternator on the 140 retrofitted with a solid state voltage regulator will keep the alternator output above 14 volts at idle when the fan switches on. A generator may struggle to maintain voltage at idle with a large electric fan.

I can honestly say it’s ya thermostats rating , remove and place a lower rated thermostat in and your golden see it all the time when folk get sold 86 degree thermostats replace with a 76 degree and you will be fine 😎👍 also that’s going to cost you peanuts to try / resolve and a few mins of your time

Kind regards
Robert.w

Greg, I run a plastic radiator shroud on my MGA (stock puller fan) and it makes a big difference in how much air is pulled through when compared to no shroud - at least when the car is sitting still. At speed, I suspect it has less effect since the air is otherwise being pushed through the radiator by the car's movement.

My shroud and fan tip separation is quite tight, maybe only 1/4".

I can't remember what drives the water pump on my PV444, but assuming that your water pump is driven by a pulley, it might be worth considering a larger pump pulley. The theory is that if you slow down the water pump, that will slow down the water moving through the radiator and allow it to cool longer before returning to the engine. I suppose a whole course in thermodynamics would be necessary to evaluate flow rates, temperature differential and heat exchange, but I believe that this would work better at faster speed rather than slower.

The observation about the spacing of the shroud relative to the fan tip is correct. If you have a large gap between the fan tip in the inner diameter of the shroud opening you reduce the effectiveness of the shroud.

In the whole B18/B20 overheating / running hot discussion, you need to differentiate between 'is the temperature gauge just reading high' and 'is it really overheating'. Really overheating usually means the pressure cap is releasing and you are dumping coolant, also known as a boil over. The B18/B20 temperature gauge measurement point is at the back of the head. The thermostat is at the front of the head at the outlet to the radiator. I have a B20E which also has a coolant temperature sensor at the front of the head for the fuel injection system and my D jet has been converted to digital EFI so I can log the actual front of head coolant temperature while driving. Based upon my temperature logs I can provide a couple of observations:

- Once I am above about 40 km/hr the front of head and back of head temperatures stabilize with the back of head temperature being about 2 C higher than the front of head temperature. I have the 82 C thermostat which goes fully open at 90 C. On a hot day, above 40 km/hr my coolant temperatures measured at the front of the are probably 89 - 91C.

- If I come to a stoplight, the back of head temperature starts to increase almost immediately. The front of head temperature will start to increase; but, typically levels off somewhere around 93 - 94 C. My electric fan switches on at around 92 C and on a hot day, if I come to a stop light after driving at speed the fan will typically switching on about 10 - 15 seconds after stopping. On a vey hot day with a long traffic light the back of head temperature can easily rise about 10 C relative to the front of head temperature reaching temperatures over 100C while the coolant temperature as measured by the thermostat is still perfectly acceptable. As soon as the light changes and I pull away the back of head temperature starts dropping.

So, just because the dash temperature gauge is going quite high does not necessarily mean that the engine is overheating. Most factory temperature gauges are designed to be slow to respond so that most of these temperature swings are not seen by the driver unless the car is sitting idling for a longer period of time or is in very slow moving traffic.

The temperature increase when the car comes to a stop and idles is pretty normal. It is a combination of two things, reduced air flow through the rad which is slightly elevating the general coolant temperature and reduced coolant flow through the engine which causes the back of head temperature to rise. I have confirmed the latter because if I increase the engine speed to about 1500 - 1700 RPM I can actually cause the coolant temperature measurement to drop because of increased coolant flow through the head. Based upon the latter observation, I think your suggestion to reduce the coolant flow rate through the head with a larger water pump pulley would be a bad thing.

The take away - is the engine really overheating or are you just getting that normal temperature increase when the car comes to a stop with the engine idling? If the car is not overheating / boiling over and the sight of the temperature gauge creeping up bothers you, you can do the dodge of opening up the interior heater valve and shutting off the heater doors which allows increased flow through the head and some secondary heat rejection through the heater. You can also put a mechanical by pass valve around the existing heater valve which allows increased coolant flow through the head via the external heater circuit without heating the car interior.