Cooling issues on 92 SE

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MetBlue
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Re: Cooling issues on 92 SE

Post by MetBlue »

It's apparently from a Fiesta, but I have no idea what version
Confirmed, fans off Fiesta's fit. The one already on my car had the Ford Part No 93FB-8K620-AA still written on it, so quick eBay search found a match and I await delivery.
Blank cap turned up today, so I'll be waiting until fan turns up, then off with the tank for a flush, on with the new fan and complete checks to ensure all working.
Been thinking through the cap situation. I agree makes no sense to have 2 pressure relief caps. That's definitely wrong. From trying to rod out the connecting pipe I know the pipe is always open to water flow to the expansion tank side, irrespective of the state of the relief cap (if fitted to front tank). Hence it shouldn't matter which cap is blank and which is a relief valve. They are both effectively closing the same container of water and air. The only logic in having the relief on the rear larger diameter, is that it will help keep the connecting pipe from blocking. Thing is, there needs to be an overflow pipe on the cap that is relief cap and on these tanks, that's the rear, larger cap. If front cap is the relief, water will just leak out the top of the cap! And drip down tank and wing onto the exhaust.
Tony
What goes together.... Must come apart.

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Re: Cooling issues on 92 SE

Post by CHRISYD »

My caps are the one with the ears and spring on at front, round one with no spring at back. Then i suppose when the pressure gets too much, the spring rises allowing water to exit the overflow tube and down onto floor near rad.
I REALISED YOU CANT LIVE WITHOUT A LOTUS!!! Until now :oops:

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MetBlue
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Re: Cooling issues on 92 SE

Post by MetBlue »

Yes. Exactly.
The ears or not don't necessarily define if it's a relieve valve though. If there's a spring loaded seal underneath, it's a relief valve, if it's just flush with a rubber seal, is a simple cap.
The cap I bought off ebay, has ears and no spring. Just a seal.
Tony
What goes together.... Must come apart.

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Re: Cooling issues on 92 SE

Post by barker_001 »

Lotus-e-Clan wrote:
Mon Jul 20, 2020 07:30
One other significant thing to consider.

If the link tube between the two chambers is blocked then the first chamber will over-pressurise and eventually leak. These tubes tend to block if you don't have fluid in both chambers at all times ..or the first chamber isn't completely filled.

It's a bounder to unblock too ... :)
I made sure mine was clear by pushing a piece of strimmer cord through it from the front chamber - flexible enough to go round the 90 degree bend, but thick enough and stiff enough to remove any crud. The tube ends very close to the bottom of the rear chamber so it's quite hard to see the end of the cord. I did it by pushing the cord through until I felt a definite "stop", then looking for a disturbance in the traces of coolant left in the rear chamber (probably 1/4" deep when the engine is cold).
Bryan

1990 Excel SE

"Look, there's a Ferrari..."

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Re: Cooling issues on 92 SE

Post by CHRISYD »

I checked my tank today and noticed i made a mistake, the overflow is on the rear half not front. the openings are different sizes so my eared spring cap only fits on the front so ive got the round springless cap on the overflow rear end. seems odd but thats how its designed.
I REALISED YOU CANT LIVE WITHOUT A LOTUS!!! Until now :oops:

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Re: Cooling issues on 92 SE

Post by TrevorK »

Lotus-e-Clan wrote:
Sun Jul 19, 2020 22:11
Mine is a 89SE - essentially the beginning of the later spec cars. Not much changed after 89.

I bought my 2 owner Excel with 38K on the clock twenty two years ago. The header tank caps are entirely original OEM. The FRONT cap is the pressure relief variant. The rear cap is PLAIN (and of a larger diameter than the front).

It makes no sense to have two pressure relief caps.

It also make no sense to have a plain cap on the front and a pressure relief cap on the rear.

Think about it - plain on front, relief on rear. With a pressure cap on the rear (plain on the front) the water pressure building within the main system now DIRECTLY presses on (relies on) AIR within the rear chamber to raise the pressure relief valve (assuming the rear tank is only half full) . Air is compressible, water is not. Essentially you want the pressure relief valve resisting non-compressible water pressure within the first tank to stand a chance of proper consistent water transfer to and fro between the two tanks. Otherwise, governed by air under pressure in the second tank you will force AIR out of the second (rear) tank at 10 psi then create negative pressure (vacuum) in the second tank as the engine cools and the relief cap closes. The relief valve in the second tank will re-seat according to falling air pressure in the second tank against variable atmospheric pressure on the outside.
Interesting. My car has what look like the original caps with the blanking cap at the front and the larger, non-eared pressure relief cap on the rear. I think the logic is the the front is filled with coolant with the engine cold and the rear has enough to at least cover the bottom of the siphon tube. As the engine heats up, the coolant expands and some gets pushed into the rear chamber. As it cools, it gets drawn back into the front. If the pressure gets excessive, say, through there being steam in the coolant, the rear cap will lift and let out any excess, air first. When the engine cools and the pressure drops, a valve should let air back into the tank. This arrangement helps prevent loss of coolant when the car heats up.
What car is that?

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Re: Cooling issues on 92 SE

Post by DavidOliver »

Why the two tanks? Why not one with a pressure relief valve and as large as the two and avoid a cloggable transfer pipe?
After all the tank is not a swirl tank, it does not have a constant flow through it?

Dave the cog.

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Re: Cooling issues on 92 SE

Post by MetBlue »

Why the two tanks?
Fair point. My thought is that the system is designed to run with a volume of air that will compress. If only one large tank, correct water level would be about 1/3 full ( front tank is smaller than rear expansion). Knowing level is correct would be difficult and I'm sure it would get overfilled by the unknowing.

Back to my original problem. Have now diagnosed I had 3 problems. Biggest fault was fuse 18 was blown, so no power to otter switch, hence nothing to switch fans on. Then I had the seized fan on one position, now replaced with the direct fit Ford fan motor, including fan blade ( I now have a matching pair of yellow fans 😊). Then I had 2 pressure caps fitted instead of one blanking cap.
All now sorted, so next hot day, I'll test it and see if fans come on OK.

Another question : How on earth does the coolant level switch work? I have resistance with empty tank across the terminals and no evidence of it changing as the water rises over the sensor. Should the sensor be insulated from the tank so it is open circuit with low water? Mine has some contact to the tank as soon as inserted.

Tony
What goes together.... Must come apart.

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Re: Cooling issues on 92 SE

Post by Pete Boole »

Yes - the level sensor should not touch the tank. Do you still have the earth tag on the tank?

The reason for "two tanks" is height - you have a constant head of coolant when it's working correctly.

Pete

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Re: Cooling issues on 92 SE

Post by DavidOliver »

ON A SYSTEM REFILL how do you fill the tanks and to what level?
With both caps off when you fill the front tank the rear tank will also fill up.
You then put the caps on, start the engine and coolant will be pressurised past the rear cap valve to overflow
up to working temperature. When the engine is stopped and the system cools, air will enter the rear tank
to a volume equivalent to the volume change of the complete coolant engine/radiator system over the temperature cold to hot range.
Any air initially trapped in the engine system which reaches the reservoir tanks on start-up will reach the front tank and stay there.
Not all the air trapped in the system gets flushed through to the reservoir tanks.

A suggestion for obtaining correct levels. Always remove both caps and fill to full (both tanks)
Replace both caps.
Start engine and drive to normal driving temperature.
Leave engine to cool (overnight)
Repeat filling tanks to full. This will produce a second overflow when restarted.

The system working head of coolant pressure at working temperature is effectively that produced by the relief cap.

Dave the cog.

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MetBlue
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Re: Cooling issues on 92 SE

Post by MetBlue »

Yes - the level sensor should not touch the tank. Do you still have the earth tag on the tank?
Earth tag is still on tank. I thought it wrong that I got continuity as soon as sensor started to enter the bushed hole.
I assume an open circuit reports a low level condition and when sensor is under water, the earth leakage is picked up as a good signal?
Will try removing the spade and see if warning light come on.

Tony
What goes together.... Must come apart.

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MetBlue
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Re: Cooling issues on 92 SE

Post by MetBlue »

Have now diagnosed I had 3 problems.
Make that 4.
Let temp gauge get just over 100 deg C yesterday and fans still not coming on. Otter switch now joined the party.. May experiment with orientation as earlier in this thread before partial drain down again.

On water level switch, removed spade and Fan Fail light came on! Oh well. At least its a warning light.
Tony
What goes together.... Must come apart.

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Re: Cooling issues on 92 SE

Post by Lotus-e-Clan »

I’ve had no broadband since Thursday 23 July due to a fire at the Northern BT /Virgin media exchange in Newcastle! Unbeknown to me my router required a manual reset, otherwise I would have posted this a lot earlier.

OK Chaps, confession time … 😐

Spot the weirdness… 😉
Image

Image

Image

I muddled the operation of the OE Excel SE expansion system with the OE Clan expansion system. :oops:

:mrgreen: I confess, and I’m currently wearing a hair-shirt as penance. The original Excel SE indeed had a small plain cap on the full front tank with a large pressure relief cap on the second. … exactly like Pete Boole and Trevor described.


I now have PLAIN caps on BOTH tanks (same for Clan). It has been like that for so long that I had ‘normalised’ it. The big plain cap on the second tank had become a std OE fitment in my stupid old head! (see pics above)

As you can deduce from the dual plain caps, my Excel has a non-pressurised Evans waterless system (same for Clan). Only a small unpressurised volume passes between the two tanks (Evans expands just a little). The second tank volume remaining ½ full when cooled. It’s one of the plus-point reliability features of an Evan’s Waterless system.

Sorry everyone!! My bad! :oops:
Peter K

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Re: Cooling issues on 92 SE

Post by gusexcel »

Image

somehow your post did not show up until I posted this, but this is the insert sheet from my owners manual confirming your correction

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Re: Cooling issues on 92 SE

Post by richardw »

Like PeterK, I use Evans Waterless Coolant. Been in the car for 5 years, no problems, and no worries about pressure in the system. It is probably also better for the water pump as it is self-lubricating.

Cheers, Richard
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