Overheating - Rad fan? Thermostat?

[rubberjohnson]

Hi all,

The little lady (not the missus, the car, obviously) had a bit of a strop on the motorway this weekend. Temp guage suddenly rocketed up to the red. We've already lost one Puma after blowing the head gasket when a coolant pipe went, so I stopped as soon as possible and had a look. Nothing obvious, coolant OK, etc. Five minutes later temp is fine, bang in the middle of the dial. Moved away and up goes the needle, but as soon as I take my foot off the accelerator it drops again. Foot down: temp up. Foot up: temp down. Almost instantaneous.
Worried I may be losing coolant or the water pump is broken I switch on the heater blower to check coolant is in the pipes - yes, very hot air...AND the temperature drops back to normal. Heating off, temperature up; heating on, back to normal. So I drove the rest of the weekend with the heater on (and yes, it was a bloody hot weekend!)

First thoughts were that it can't be the pump or a coolant leak, as explained, so must be radiator isn't doing the full job and the heater matrix is good enough to take the radiator's job on, although the pipes to and from the rad were hot so I think coolant was getting round. Maybe the thermostat stuck half open? My mechanic suggested testing the rad fan so I idled the engine and revved a bit when the missus was back home from work with the car last night and the fan came on fine. (Also, I couldn't replicate the overheating problem, naturally). But I notice the aircon doesn't work; the lights come on but no discernable drop in engine revs and the fan doesn't come on when the aircon is on. I've read on this site that it should be coming on at a low speed with the aircon (to blow air over the heat exchanger) and there are two relays, one for high speed fan and one for low speed (C161 and C160)

I've got the workshop manual and I'll follow all the problem solving there (which is basically testing each fuse that may be involved then moving on to the WOT relay then the A/C switch relay, etc.) but I just wondered if any of you, in your infite(!) Puma wisdom had any suggestions straight off the bat. I find it very odd that the temperature gauge (and thus the engine temp as the gauge seems to be working properly) is reacting that quickly to revs and air flow. Although I suspect something wrong with some part of the rad fan control since it's not coming on with the aircon (although that could be a compressor problem or just no gas I guess), I was driving at a speed sufficient to not need the fan anyway.

Any pointers/suggestions/do's and dont's gratefully accepted, cheers.

Rob

 

[rubberjohnson]

Hmm. I have replaced the control valve once - the old one used to click all the time when it should have been fully open or closed. Maybe I'll replace that again. But would it affect engine temperature that much?

And no, to be honest, last night I don't think it ever ran cold air, just stayed hot. I'll check the voltages to the control valve tonight, too then. It's a pain if that's gone again, I'd only just got rid of the last airlock!

 

[quest63]

I'm no expert but I have heard the vanes on the water pump can become loose and spin on their shaft at speed so they aren't moving water or aren't moving as much water. Also possibly the auxiliary belt may be slipping at speed?

Personally I would change the thermostat as its the cheapest option and while the housing is off have a feel inside to see if any water pump vanes are broken and then take it from there.

 

[3dcandy]

I have this but not quite as bad and my thermostat needs doing....
Started with the HCV as it was obviously busted (could see it was actually leaking a small bit...) and next up is thermostat as temp has gone down during normal driving but the radiator does not get warm at all...

 

[CherryVimto]

Aside from the thermostat, I would possibly look at checking the radiator for blockages.

Maybe when you're driving gently, the flow through the radiator is enough to keep the temperature constant.
When you stick your foot down (more engine load creating more heat) the sudden surge in coolant flow may be too much to flow through the radiator fast enough to cool it.

But, as the coolant flows from the passenger side of the radiator, then to the thermostat, a faulty/sticking half open/close thermostat could theoretically cause the same scenario.
If the thermostat is stuck closed, the passenger side end of the radiator will get warm but the middle should be cold/ambient temperature**

It seems strange that the coolant temp increase is almost instant though.

This may be totally irrelevant but.....
If you have a digi dash, you could do the diagnostic program and cycle through to the coolant temperature and see what temp the coolant gets to. You could possibly get a hand held thermometer with a probe and put that in the header tank (being careful not to burn yourself) and see if the temp reading is anything near to what the dash reads.

** bit obvious, but don't go putting you hand through the rad fan if the ignition is switched on.... you could end up losing some fingers!

 

[rubberjohnson]

Well, the HCV seems fine, getting cold and hot air normally. Air con still not working but all electrical tests from the workshop manual so far have been fine. Maybe it's leaked the gas and just won't run until there's some pressure in there.
I'll finish those tests tonight and start thinking about the thermostat.

And it looks like I may have an oil leak. And a chipped windscreen. It never ends... :roll:

 

[quest63]

The rocker gasket is favourite for the oil leak

 

[rubberjohnson]

Update...
Changed the thermostat, old one seemed alright and opened in hot water, but I put a new one in anyway. Maybe it didn't open all the way, hard to tell. Flushed the rad, filled with Rad Weld Speedflush and water, got that through the system, cooled it and drained, flushed again and re-filled. All seems OK, but the proof will be in the test drive! Felt the pump vanes whilst I was in there, it all seemed to be in order.
HCV definitely working properly, I can feel it ticking when on half-heat and it blows hot and cold (like the missus ).
All the air con electrics seem fine, it comes on if I bypass the compressor switch so either that switch has gone or, more likely, it's just low on refrigerant. Time to call 'we chill any car', I think.

 

[rubberjohnson]

Well, got the air-con re-gassed and that seems to work again.

Still overheating though. I've read enough on various websites to now know that this is a fairly common problem with Zetec engines although there never seems to be a consensus on what causes it. Annoyingly, people often don't come back with a final post on how (or if) they cured it. <_<

So I'm starting with the cheaper options, like a new expansion tank cap (although I'm sure mine is fine, seems to be holding pressure) and I've tried purging it of air a few times. What's the best method - letting it run hot then opening the cap to suck the air locks out, or just running it hot without the cap for a while? Both seem to get mentioned.

Also buying a new heater control valve. First thing in the manual when only getting hot air inside (this is when driving only, always behaves itself when testing at home even at sustained high revs) is to check the valve is pulsing on half-heat. If it is, but still only hot air, then change it! Can't argue with that, so that's first up. Next will be a new rad and hoses. I can't see how the HCV would make the engine overheat, but I'll try anything.

Money, money, money. Pity Costa Rica are out of the World Cup, the missus had a quid on them to win - at 4000/1!

 

[yogi1kenobi]

Havin similar problem m8 .. When i take for drive temp shoots up within 1/2 mile... Noticed right side hose cool rest red hot.. Thermastat?
Can you tell me location of relays c161...c160 as had to direcly wire fan as was nt comming on at lo speed

 

[rubberjohnson]

There's a good guide to relays and fuses under the bonnet for both variations (pre- and post-2000) here:
http://www.projectpuma.com/viewtopic.php?f=21&t=6195" onclick="window.open(this.href);return false;

 

[rubberjohnson]

I've got a Ford heater control valve now, I'll try putting that in tomorrow. Got home today after nursing the car home - three quarters up the temp guage on average, swinging between normal and into the red all the way depending on speed, hills, throttle, etc. Really seems like a radiator problem, but hoses in and out were warm when I got back (top hotter than bottom, but neither really hot). Fan was on. The expansion tank hoses were red hot, way hotter than the inlet hose to the radiator, so maybe the water pump not doing it's thing properly? Or the hose collapsing?? I'm going to try ANOTHER thermostat too, an official Ford one.
Argh, it's so annoying! :x

 

[rubberjohnson]

SORTED! :grin: :grin: :grin:

I can hardly believe it, it seems to be fixed! And what was it? As many people have found out in the past...the heater control valve. Changed it yesterday, ran it up to temp to bleed the system then drove home with the dash in diagnostic mode to keep an eye on the temp. 89-90C all the way. Up to 102 sat in traffic then the fan cut in and straight back down into the 80s.

I'm so happy - and de-stressed - I can hardly tell you.

So for anyone who's found this from searching for an overheating Puma, or Zetec, I can only add my agreement to the people who suggest changing your HCV. If you're getting hot air when you blower is set to cold your HCV DOES need changing. Get a proper Ford one, £40. There's absolutely no reason it should affect your engine temperature, but it does.

Thanks to everyone who's suggested solutions. Fantastic forum.

:thumbs:

 

[red]

stupid part.

 

[YOG]

Here's some previously posted information:

How does the heater control valve cause overheating faults, surely the water will still circulate but not through the matrix?
"It's the weird stat arrangement. The wax pellet faces the radiator, not the hot flow from the head, creating a Catch-22 scenario that the wax pellet only gets hot water to open it - once the stat has been opened.
To get round that issue, the heater return flow was plumbed all the way around the engine bay just to warm the back of the stat. Once the heater valve sticks half-way, it doesn't feed enough hot water to the stat and so it doesn't open properly - just as a fitted-the-wrong-way-round stat wouldn't.
The heater valve also contains a by-pass valve and either feeds the matrix or diverts the flow back into the thermostat housing where it goes past the wax-pellet end of the backward-facing stat and heats it."

 

[3dcandy]

After a good while researching this it appears that the Puma thermostat housing has an unusually wide bypass to the hcv. If the hcv is permanently hot then the engine can actually cope for a large while without water passing through the thermostat into the radiator. However, this is the point, what happens is that the water mainly just passes through the heater matrix till that can't cope then the temp shoots up and it passes through the radiator and so on and so on
Thus you get your temp gauge all over the place. In my case the actual hcv is ok but the dash panel is knackered...

And of course, with the info above this is what happens...

 

[rubberjohnson]

Ah, it all (sort of) makes sense now. Although not why they designed it that way. :?

Anyway, just the oil leak to sort and a wheel bearing to change (for the second time in as many visits, a wheel bearing is on the way out DIRECTLY after the car has been to a tyre place for tracking/balancing - I don't know what they do, considering they don't necessarily even take the wheels off, maybe it's just a coincidence :roll: ).

Otherwise, I'm a very happy chappy.