Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 2002 Zetec cooling issue

Hello all, I am having a small issue with the cooling system on my 2002 Zetec 4/4. I have just had a new alloy radiator and expansion tank fitted by Tim Ayres, amongst a load of other stuff. Before I let Tim have a look this week, I wondered if anyone has experienced anything similar.

The issue seems to be the expansion tank cap - the car runs well, gets up to temp as it should. As it gets up to around 100 degrees the expansion tank starts to fill from the bleed pipe coming from the stat, and the other one coming from the rad. So far, so normal I believe? But the cap then starts to bleed off steam, which gets quite violent until the fans kick in. At that point the level in the tank drops back, and the steaming stops. I can take the cap off at that point without issue - there is clearly no pressure in the tank. The cap itself does not seem to screw on that tight, which is something I have not encountered on other engines, but maybe it is correct?

When this initially started, the tank was venting coolant, but that has now stopped as the level of coolant has fallen. It has dropped below the MIN mark on the tank, but there is still a low level of coolant visible in the bottom of the tank - I seem to recall reading Phil Benfield advised that that was satisfactory and that the level did not need to be on MAX or even at MIN.

I am sure Tim will be able to sort it soon enough, but in the meantime and to aid my understanding of the system, does anyone have any views or thoughts on this?

thanks

Mark

The tank is fro. FORD so the lev marks won't be right as it is in different position. Just make sure there is some fluid iin it.

What pressure is the expansion tank cap rated for? Is the seal correctly installed? It sounds to me like it's not allowing the system to reach its correct pressure maybe? If that's ok, is there a chance (highly unlikely) your cooling system is being over-pressured by a head gasket failure?

As you say, Tim will undoubtedly sort it out.

THanks both. There is definitely coolant in the expansion tank, but I don't think it is holding any pressure. Not sure what pressure it is rated at, but the handbook suggests it should be removed carefully when hot as steam may escape. Mine does not seem to be holding any pressure at all - it does not seem right that with the car at full operating temperature, and running at idle, I should be able to remove the pressure relief cap with no apparent loss of pressure. That indicates the cooling system is running at atmospheric pressure which is clearly wrong.

Pretty sure the head gasket has not failed - no reason why it should have done so, the car was fine previously and the only thing that has changed is the radiator replacement, so I am currently thinking the expansion tank and/or cap might be dud. It would be very useful if any 4/4 Zetec owners here can tell me:

- is the expansion cap on your car on tight?
- if you try to remove it when hot, does it appear pressurised?

thanks

Mark

The roadster has from memory the same plastic expansion tank from a fiesta as your the tank & it pressurises I think to 7 psig. The cap is tight when hot.

This is a custom tank but with a pressure cap


And this is mine with the same pressure cap


I found the level after a while as the rad slowly vents air from the header. If the heater works then I expect the level is OK.

Thanks John. I think mine is the same, looking at the link below it seems to be from a Ford Transit:

https://www.ebay.co.uk/itm/155068723516?fits=Car+Make%3AFord%7CCars+Year%3A2002&epid=4033842687&itmmeta=01HTD4DG6J71RHMB2G8M56JCCV&hash=item241ad0f13c:g:L3wAAOSwstplHnuS&itmprp=enc%3AAQAJAAAA0DG9Evudbr3GOj1iHO3WF7MlvmZY3kOZcKbBUL69gKwiGJB%2BMJgs3npumnZwUUkJIXwDaf9aLzHFm1D3ilGzaPCjO54AahSfUjHdnRt8x%2BSYk7R7kpTo9i8XJWrpHAU96ehoBEHnUEzBdrdBbjPVRJZK1BucPyzvbTUL4FDvAs1KzcRgFwkBFUl9QAnSoNJWL7h%2F6rFXdJAGlXQ65HzRafp3YMXtZAo1atLGIijQUUTaobiYnqzFxVjbMXTN11bIVk8oB6ARfc3WVlm87fSCzGs%3D%7Ctkp%3ABk9SR66DtqTTYw


The heater works well, did a few hundred miles this weekend and apart from the occasional boil over all was well. The TRansit cap appears to operate at 21psi, not sure if that is correct for the Zetec. But the cap on my new expansion tank is not tight - it appears to be cross-threaded and will only tighten so far. I don't think that is correct.

Mark

The cap should be tight and you should not be able to remove it without the system first cooling down.

My old Zetec had a "proper" old style metal pressure cap with a metal expansion tank.

However my Roadster has the later style plastic cap and I think it would be possible to cross thread it and therefore not get it fully tight.

Have you tried removing the cap and then carefully trying to find the old thread path before cross threading.

There is a rubber seal in the cap, maybe put some vaseline on the seal and see if it rubs off on the tank neck. Or engineers blue of course.

Thanks Bob, I think this all points more towards the cap being duff - I have tried every which way to get it to tighten down, but it will go so far then slip round again. With the car running and hot, the fans kicked in, then stopped after a couple of minutes, at which point I could remove the cap easily. It was hot, but there was no pressure behind it.

Mark

What's been said about the header tank levels is correct, some show right on level others usually low' It's not a design specific tank and it would seem slight engine variations make a difference in cold and hot levels!
Did it have any of these issues prior to the modifications being made?

You have had yet another aftermarket header tank option fitted and perhaps its expansion capacity just isn't great enough. If the cap isn't sealing then that will change the boiling temp as will its pressure relief function/capability. you seem to have all those associated symptoms. Is the header tank position now lower as its repositioned on the bulkhead and filling with fluid prior to full pressurization of the system. Could be that the thermostat is also not functioning correctly or is of the incorrect operating temp type, ie. replaced as an incorrect item. Is it actually boiling? if so, both the cap seal and venting pressure are indicators of this scenario and the thermostat seems to not be opening early enough. The temp gauge in the car might show 100'c but is it? a temp target of 90'c is the desired so ascertaining the true temperature is required. Have you got the old header tank, if so refit this and see what happens. might answer a few questions.

In my time I have seen all sorts of things from paper towel packed into the bottom hose outlet to stop it dripping on the mechanic working under the car and then left in when reconnected. Blanking plugs left in rads and hose outlets to faulty new thermostats. There was a time when you had to check every new stat prior to fitting, both function and temp!

Hope you get to the bottom of it soon!

Head gasket failure, you'll get white exhaust gas like a kettle boiling steam! and I'd think a greater loss of coolant in the system.

Oops1 didn't see the last two posts come in! yep that cap is definitely duff! and will alter the boiling temp .