Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Engine running cool but losing coolant

Hi all. Interesting question time...

I have a 4/4 Zetec 1.8 from 2004. It's done the grand total of 120,000 miles (yes, really!) Over it's time, it has had its fair number of replacement radiators but the last was a long time ago.

Over recent months it has been running cool than normal but has been losing coolant too. I've had it checked by my local dealer, who flushed it through 4 times and replaced the expansion bottle, so I can actually read it. They didn't replace the thermostat and I've not checked to see if it works (it is, after all, what I paid them for! Not been back to them yet.)

I then drove it back home and found it had lost coolant. I drove it to work and back and had to top up both ways - 21 miles each way.

Today I ran it up to temperature on the drive. The radiator cooling fan kicked in at around the usual spot on the dial and I could see no coolant loss around the radiator top or bottom hoses, or any other hose around the car. The garage floor is dry.

The oil is clean and the oil filler cap has no indication that there is water in the oil - I've seen that terrible mousse before on an old A series engine I had, and on a Renault engine too.

So, any ideas? It could be thermostat, I guess, but that doesn't explain the coolant loss. I've not checked the heater matrix to see if that's leaking. Is there anything else I need to look at or get checked out?

Thanks for reading and any advice :-)

Sort of sounds like the head gasket is leaking putting more pressure into the cooling system and forcing coolant out by way of the overflow tube. Only leaks when the engine is running. Should be exhaust in the coolant. This can be determined by the Dealer or knowledgeable mechanic.

It can be a bit of a daft one but if air is trapped in the cooling system then in certain places there is no water and it overheats and pushes water out the expansion tank.

That engine in Ford cars has a name for trapping air and garages just fill up with coolant and give you the car back as most punters do not want to pay for an other half hour to bleed the system.

Mix some water and antifreeze. Take the car to a steep hill and park it with the front up the hill. Leave for a while to cool down. Engine switched off.

Be very careful and with a towel over the filler cap remove the cap.

Set the heater to hot with the heater fan on.

Squeeze all the hoses with the engine off to try and burp the air out.

With the premixed fluid handy start the engine and just stand there for 15mins to 20 minutes slowly adding fluid if the level goes down.

Now be very careful of the radiator fan and go round and burp all the hoses again.

As the thermostat opens there my well be a quick decrease in fluid level. Fill the fluid to the high mark and go for a drive. What is the heater output like heat wise is it as always or not just as good as it was.

If that fails as Button has mention a cooling system pressure test may well find a problem like a head gasket but I would bleed the system first.

Certainly try Eddie's theory first before my idea. I would have thought the mechanic who first worked on Your 4/4 would have checked the coolant. Standard practice I thought.

I'd be inclined to do a compression test on each cylinder and remove the thermostat to test its opening temperature independently. There will be spec numbers to compare against in both cases.
It's certainly not impossible for a head gasket to fail and not result in oil contamination. I will say though that Ford engines are outside my experience.

No white smoke coming out of the exhaust by any chance?

I think the 2 symptoms are probably unrelated. I would have expected to see some evidence in the oil if the head gasket had gone and you would notice a deterioration in the running and maybe more smoke in the exhaust.

My guess would be that the air was not bled out when the radiator was refilled and it can take couple of runs to find it's way out on it's own if you don't bleed it.

This has happened to me a couple of times on my Silvertop Zetec when I've changed the radiator and pipe work but it did eventually find it's own level and settled down.

Keep an eye on it and obviously investigate further if it doesn't settle down.

How much water do you need to add to top it up?

The low engine temperature is interesting because I had the same problem in the early days.

When I picked the car up from a dealer near to you I noticed that it took a very long time to warm up and indeed in March last year the temperature never really got above about 80 degrees on a very cold day.

I was told that some cars are like that and we discussed whether the thermostat should be checked but as the year wore on and the weather picked up the coolant temperature also started to rise up to about 85 ish (Which is still too low for a Zetec.) and my warranty period had run out so being new to Morgans I just left it.

Later in the year I started to notice some leaking from the radiator around the top hose so I decided to fit a new Sifab unit and at the same time I changed some hoses and decided to take a look at the thermostat.

I dropped it in a pan of boiling water and it started to open then I let it cool and it closed so thermostat working ok.

However someone had drilled 2 holes in the flange and this had the effect of allowing water to bypass the thermostat and in effect leave the thermostat open at all times.

In hot weather this might have the effect of keeping the water a bit cooler but in cold weather it stops the coolant getting up to the proper working temperature which is very bad for all engines but especially the Ford engines that are designed to run around 92 - 95 degrees or even slightly higher.

I was told this is a mod that some people do but for the life of me, I cannot understand why.

I changed the thermostat without holes and the system now warms up quickly to the correct temperature and stays there regardless of the ambient temperature. That is what Ford designed it to do and if the rest of the cooling system is in good shape that is the way it should be run.

You may not have the same strange mod that I had but the symptoms are the same and whilst the thermostat is a bit fiddly to get at, it should be checked.

I don't understand why your dealer would not check the thermostat with these symptoms especially as your system was already drained but my dealer was also reluctant to strip it out to check and I found the problem myself.

My Zetec is a Silvertop and your Blacktop may not be exactly the same but I think the thermostat operation and plumbing is very similar.

Good Luck

I find a lot of garages want car in and out as fast as possible and do not want to delve as it may be an expensive job that makes the owner not very happy. They think they are doing the car owner a good turn be reducing the owners invoice value for the work.

Is your Header/Expansion tank the highest point in your coolant system?

If not then it is common to have coolant related issues.

I'd imagine your Mog hasn't been modified without you knowing about it?

When bleeding via any induced tilting of the car on a hill or otherwise (car jack or ramp etc) try and keep the header at the highest point, that way air will escape.