Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Mulfab radiator? (4/4 focus zetec)

Good morning Bob, I thought I'd replied to this on my phone so if this comes twice my apologies.
The fan will switch on at different indicated temperatures depending on the engine load so when idling it'll be about 103, when on the road it seems to be about 100 but yesterday the indicated temperature once thoroughly warmed up was 100 at 50mph and it never used to run that hot at such a low speed.

It's a 1.8 black top Zetec.
I will try and see if there's any air in the system first and then check the thermostat I think. i've also ordered a non contact thermometer so I can check temperatures around the system.
The "cooling temperature" thread is interesting and will give me some comparisons.

Hi Simon,

Mine is a silver top but I have a new 2.0 blacktop in the garage as well as I'm planning to change it later this year so I can do a direct comparison.

I have a SiFab radiator and in terms of cooling capacity, I think they are very similar so I doubt if it's a radiator problem as such.

The big difference comparing the silvertop and blacktop is in the thermostat housing.

Although the basic water flow is the same and the overall shape is very similar, the blacktop takes the temperature readings from a sensor in the head and reads the head temperature rather than the coolant water temperature whereas the silver top has 2 temperature sensors in the thermostat housing. One for the ECU and the other for the gauge.

The blacktop and silvertop are very similar in most respects and I would expect that, if your cooling system is working correctly, the water temperatures would be very similar.

My engine sits at between 90 and 95 degrees all the time (on the gauge) on the move and only gets hotter when I'm stuck in traffic. It sometimes spikes a bit higher if I suddenly start doing a few full power acceleration runs but that's just the lag in the system while the thermostat catches up with the sudden increase in temperature and it the returns to normal quite quickly. Vice versa if I suddenly go from hard driving to coasting.

It's a double acting thermostat, as is yours, so the flow of water varies between the main cooling circuit and the bypass circuit to keep it within range no matter what the ambient temperature is.

I've driven mine at temperatures as low as freezing and up to about 35+ (Blenheim if I remember correctly) and It's always stayed within that range.

The fan is set to come on at 98 and go off at 95.

I don't have any air flow modifiers fitted or exhaust wraps etc.

It is entirely possible that even though you are showing 100+ degrees at the head that the water temperature is lower and more in my range but you can only check that by fitting a sensor into the water hose close to the thermostat housing.

I'm assuming you have the stock ECU and that this is controlling the fan.

What is the temperature range of your thermostat? It's stamped on it.

When I bought the car, someone had modified the thermostat and It took forever to warm up and indeed it wouldn't get above about 80 degrees in the winter.

However, when I changed the rad I put the whole system back to standard with a new thermostat and since then it's all worked fine.

IMHO it has nothing to do with the airflow or the radiator capacity and it may well be that having the sensor in the head will show different readings to the actual water temperature.

When I change engines, I'm going to use the silvertop thermostat housing so that I can keep the existing temperature measurement.

Hope this gives you some more ideas and you can PM if you want to get into more detail.

Hello Bob,
Thanks for taking the time to give such a comprehensive reply and it does explain why the temperature varies with speed if the reading is coming from the head. I still can't make out exactly what's going on but it seems the better I get the air flow the higher the indicated temperature for any given speed so whereas it would sit at about 98 at 50 - 60, 100 at 70 and 102 ish at 80 (not that I ever do 80 you understand) with the fan cycling on and off it is now reading about 100 even at 50 and 102 at 70 but I can't hear if the fan is coming on or not. I THINK the fan must be activated by a different temperature sensor because it comes on at about 100 when idling in traffic and stops again quite quickly even though there is little change to the temperature readout. It does not run when on the move at 100, more like about 102 or 3.
I am wondering if the water is now cooled further returning to the engine and whatever sensor works the fan is remaining happy although the readout from the head is higher, is this caused by the thermostat being closed further due to the cooler water entering - who knows! It would seem I may have wasted my time but the point of all this is that the fan relay failed once when queuing for the Eurostar which resulted in boiling water and steam being ejected all over the passenger side windscreen. If this happened at speed heaven knows what would be the result but I'd rather like to avoid the need for the fan anyway!
I think I'll leave it for a while and see what happens when the ambient temperature is higher.
Strange yours is steady at 90 - 95 assuming the set up is the same as mine.
The thermostat I fitted came from Melvyn and was the same rating as the one removed which I think was something like 98 - 102
Again, thanks for your response, it's very interesting to compare.
Regards
Simon

Simon,

You say the the better you get the airflow, the higher the temperature for a given speed but that sounds counter intuitive to me.

Are you sure the mods you've made have improved the airflow?

My thermostat is rated at 92 - 102 which means it starts to open at 92 but is not fully open until 102 so in theory my engine could also get up to 102 but because of the radiator capacity and the relative ambient temperature and engine load it seems to sit around 95.

That means that my thermostat is never fully open at normal operating conditions so some of the coolant flows through the rad but some still flows via the bypass circuit showing that the radiator has a surfeit of cooling capacity for my engine output and ambient temperature .

On a very cold day the thermostat hardly opens at all so the temperature sits nearer to the 92 lower limit.

I can only see one temperature sensor on the blacktop but you may have a second gauge or fan sensor in the water hose lines.

You can't avoid having a cooling fan in the system and I think it was just bad luck that the relay failed. It is highly unlikely that the engine will overheat on the move as the normal airflow cools the water in the rad. It's only when the airflow stops that the fan is needed. (If your system is working as it should)

Of course if your fan is constantly cutting in and out, the relay will fail sooner than normal so it is worth trying to understand what is happening.

One way to diagnose what is happening is to rewire the fan to run off a stand alone temperature sensor and see what temperature it switches on and off at.

Hello Bob,
I know exactly what you are saying because that thought crossed my mind too but the only way I could have adversely affected air flow would be if the build up of pressure in the engine bay was SO much before that air flow was actually from back to front and now I've kind of stalled it but I don't think that's the case. One more thing to try is on a longer run at 70 try switching on the fan and see if the temperature drops, if I see no change then I would have to assume air flow is sufficient. At the moment I think it's more to do with placement of the sensor and thermostat. I'll leave it for a bit and check against the non contact thermometer when it comes.
I need some warmer weather too to see what happens.

I've spent too long on this now, too many other jobs backing up that I'll have to get on with but if I ever find a solution or answer I'll report back.
Regards
Simon

You can see in the following link of a black top Zetec engine install an Alloy Rad being fitted and you can see the sensor install I went for. Tapping the water rail just as it exits the head on its return to the radiator.

http://www.talkmorgan.com/ubbthreads.php/topics/78408/7

Thanks for that. My set up is different, the thermostat is at the gearbox end of the block and I believe the fan is controlled by the ECU although I don’t know where the ECU takes its reading from.
Regards
Simon

Well I think I'm going nuts now. I received the lazer thermometer I ordered today (yes Sunday, surprised me too) so I took the car out and warmed it up, came back and the pipe connected to the bottom of the radiator was around 100 with the pipe connected to the top of the radiator about 60. I don't get that at all, surely the inlet to a radiator is at the top and the outlet at the bottom and the cool inlet to an engine is at the bottom with the hot outlet at the top.
Unable to believe what I was seeing I allowed the engine to idle for a minute or so then switched on the fan and again left it to settle and sure enough the top radiator connection is cooler than the bottom.
I am now totally baffled - is my pump going backwards or is this actually correct?
There's a van just pulled up outside with some men in white coats getting out, I think they've come to take me away!

Simon,

That could be correct.

If on warming up you had not quite got the temperature up to the bottom limit of the thermostat opening then the water would be flowing via the bypass into the bottom hose.

When the fan kicked in however obviously the water temperature should be at the point where the thermostat was open so the bypass should start to close and the main flow would be via the top hose back to the radiator.

Assuming your pump direction is correct (anti clockwise I think) then I think your head sensor is kicking the fan in before the water temperature reaches thermostat opening temperature.

Is the main hose from the thermostat to the top of the radiator getting hot or only warm?

Did you go for a good drive to get the water hot or just a drive round the block?

Hello Bob,
The indicated water temperature was around 100. I left everything ready to immediately check when I got back and the above were the readings I got, even though after a few minutes the readings were lower as you would expect still the top hose (relative to the radiator) was cooler than the bottom. The pump pulley runs anti clockwise vied from the front of the engine, i.e. same direction as the crank. This is all very strange
I should have said I was switching the fan on myself