Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Zetec cooling system advice required.

I have recently bought a car [not a Morgan though] fitted with a Zetec blacktop engine, using a Raceline water rail. It also uses an expansion tank with the small overflow outlet sealed, which seems very odd to me. There is also an overflow outlet on top of the thermostat housing at the front of the Raceline water rail, which has a short length of pipe running to the ground to vent excess water.

This doesn't seem to make much sense to me, and when running the expansion tank fills up but doesn't fully return the water as it cools, and the engine overheats and expresses water out of the thermostat housing vent onto the ground.

It would seem to me that the vent from the expansion tank should be run into the top of the Thermostat housing, thus forming a sealed system.

I would be grateful for some helpful comments on this setup please.

I always understood that a sealed system had a non pressure cap on the radiator which was then piped to a header tank where it has the pressure cap. When the water heated up it was pushed through to the header tank and when the engine cooled, the water was sucked back. The overflow pipe is usually on the header tank.

If you had the looped system you described then there is nowhere for the pressure to be released and eventually, the system would explode.

Perhaps the car manufacturer has a different system but it does seem rather odd.

Neil

Quite, I agree, and it is a little odd. Reading the Raceline website about their water rail, they even suggest that an expansion tank isn't necessary, but one can be fitted to make it easier to check the water level.

I will be giving them a ring tomorrow and see exactly what they recomend. If no one has come back with any suggestions, I will post their reply in case it is useful to anyone here.

I'd agree with Neil - there has to be room to expand/vent somewhere or it all becomes a "significant" pressure vessel.

Having read their website, it appears that the Raceline water rail is an expensive header tank. I see no sense in having another header tank other than a quick visual check of water levels. If the water is being expelled and the engine overheating, it seems as if there maybe an underlying issue. Is there a problem with the head gasket?

Neil

I'm hoping the head gasket is OK, I don't think Zetecs generally have problems with them?

I'm going to put a 'T' into the heater return hose, and put the expansion overflow pipe into it, so the coolant lost, goes back into the system, and hopefully it will find its own level, instead of pushing coolant out of the expansion tank to atmosphere.

Do you keep topping it up? If so the car never finds it's "natural" level. After a decent run (and up to temperature) is should be fine thereafter....but worth just checking the level after everything has cooled down.

I was always told the expansion tank should be about 1/3 full.

I spoke to Raceline today, and they are very adamant that a separate expansion tank is not necesary. They say that running the hose from the top of the thermostat housing to a catch tank, so that the contents can be viewed is all that is required, the coolant will find its' own level, and when coolant stops being collected by the catch tank, that is it. check coolant level weekly and put in a little, if it is too much it will be expelled into the catch tank.

I'll try and see if it works. Now, where did I store that spare catch tank..........

Will be very interested on how you get on. Please keep us up to date as its all useful information for future and current Morgan owners.

Neil

OK, I've now removed the expansion tank from the system, and routed the heater hoses through a bypass heater control, so that when the heater is off, the water can still circulate. I have also drilled a small hole in the thermostat to bleed hot water into the rest of the cooling system before the stat opens, to reduce the temperature shock when it does.

I let the engine idle for 20 minutes to completely warm through, then let it cool, put a little more water into the water rail and then took the car for a half hour drive. Apart from running a little cooler than I would like, around 65 - 70, which I understand is a Zetec trait, there was no sign of expelled water and as I had already put a switch on the fan circuit, because the ECU was activating it at around 65degs, ran it without the fan, then when I got home let it idle up to 100, then turned on the fan, which took it down to 80 - perfect. I'll take it out and into the town later this pm and see how it copes with traffic.

My fingers are crossed.

Paul, puzzled with what you have found; I have a Zetec 2.0 BlackTop (ex Mondeo) in a 4/4. As std on the Ford system there is a small (~0.5 inch bore?) bypass past the thermostat that re-enters the system just before the pump so that there is uncooled circulation through the head before the thermostat opens at which temp the bypass valve is closed, then all the water goes through the rad. then it is controlled by the thermostat. If the thermostat is working as it should then the coolant should be at thermostat temperature of around 92 C and full open 106 C. Mine sits at around 90 C (27 year old gauge and sender) only goes much above on a thrash on hot summer days.
I run a 1986 4/4 rad with an unpressurised overflow bottle that allows coolant to be sucked back into the rad, works well.
I guess you characteristics are due to the system you have installed. Surprised the std circuit was changed by RaceTech (?) Regards PJB.

Hmm, it's a bit of a mystery, but it seems to work. Essentially, the system has a Raceline water rail, which moves the thermostat to the side and n/s front of the engine. There doesn't appear to be any sort of bypass, until the thermostat opens, and the only venting is now above the thermostat housing, into an open tank, just so that one can see what, if any, the losses are. It will not suck it back into the system.

After a couple of good runs of over half an hour and 20 - 30 miles, the temperature seems to stabilise at around 80 degs c. whilst on the move, but no coolant has gone into the catch tank yet, maybe it will if stuck in traffic? Interesting, more testing is ongoing.

I wouldn't imagine at 80 degrees the catch tank would get any coolant if the system is correctly filled.

I see, so Ford think it best to allow uncooled coolant to circulate through the Zetec cylinder head before the thermostat opens to ensure there are no hot spots and local nucleate boiling, and Raceline decide to do away with this feature - ah. What's that all about then? Maybe there is not room for the Ford thermostat housing as the Zetec engine in 4/4 original fitment is about 3 inches further back than the CVH in 4/4.
Regards PJB.

Quite so Peter, but Raceline say that they have never had a problem with this set up, and it does seem to work. You can see the thermostat controling it all on the temp. guage, quite interesting to watch in fact. I'm please that the block is iron and not aluminium though......