Technical Punto Mk2 2002 1.2l overheating

[Mike63]

Part way through a repair here, findings so far. The car has been good generally, bought at 60k and have put 10k on with this the first problem. There is an overtemp light but the engine was knocking so badly beforehand that I saw the overheating on the gauge before the light came on. At that point I stopped to check:
* the radiator fan was on, so not an electrics problem
* no heat from the cabin heater, suggesting a circulation problem
* radiator seemed too cool for the situation
* cooling system was holding pressure as hoses were tight, so no major leak
* system water level was above max (due to overheating boil/expansion)

The puzzling thing to me was no cabin heat, which suggested no circulation and so a water pump fault. I'm good at mechanics but I don't know this vehicle. Since the engine was running fine obviously the cambelt was OK. It seemed unlikely that the impellor on the water pump had detached. The last cambelt change was unknown and I had been meaning to do this anyway so I ordered a water pump and a belt kit (belt + tensioner bearing), £54 from Autoparts in Glasgow.

After some browsing on this site I concluded that the cooling system was marginal and air locks were possible. I put 2l of water back in whilst bleeding the system. It was clear some had blown out as it was stitting under the radiator, probably past the pressure release but it's not entirely clear. Radiator itself is not new but no obvious leaks. So now I have a new theory - it's the thermostat. I figure I can use the internal heater to keep temperature under control whilst I go and get my parts.

Partial success. The cabin heater works so that confirms the water pump. However in-spite of this, a couple of miles later and the needle's in the red again. No thermostat at the dealer, plus it's £13! On order.

Well the thermostat's easy to remove on the side of a main road, unlike a cambelt swap. It's clear why it costs now - it's integrated into the housing. I put it in a pan of water on the stove and it opens up. Bother. Not 100% as a test because the flow and pressure make a difference, but a good indicator. Block behind looks quite clean too, but I put in radflush anyway.

Now I need a new theory, and it's this: it's still the thermostat, which has lost some wax or something that causes it to open at a bit higher temp. I notice that the heater pipes are above the nominal water level: so the cabin heater keeps the temp down until the revs are too low, when some area boils. This rapidly causes an air lock, circulation stops and the car boils. As I have a new one on order I think I'll remove the valve from the old one. However, it's only held together by spring pressure so comes apart in a non-distructive way. The empty housing is refitted. A drive test at this point shows slow warm up as expected, and even at idle it only reaches normal, with no fan.

More later.

 

[Mike63]

Bother. I tried new and old thermostats side by side in a pan of water on the cooker, and they were pretty much the same. Still, I put the new one in, filled up, went for a test run and all was fine on the temperature gauge.

My concern that I had not found a fault was confirmed when later today the car overheated again. Worse, idle was rough on start up. As expected water was missing. This leads me to the dreaded head gasket theory: a sparkplug was damp at start and also that's where the water went, via the headgasket into a cylinder. Unfortunately I don't have my compression tester with me. When cold I put another 2l in. Oil level is normal so it's not going there.

So now my problem is how to get 400 miles home, where I have garage and tools and would be able to swap the head gasket. Apart from the solution of handing over a few £100 to a local garage that is, not good timing for that.

Assumtion: there is a pinhole gap now through the head gasket from a combustion chamber to a water passageway. Can someone with a better knowledge of the engine tell me how the gasket usually fails?

 

[B3NNETT]

if the spark plug is wet then there is definaetly water getting through to the cylinder which will of had to come from a water passage way as you say. but if you are not carefull and still use it it could start hydraulicing and that is when you start to break things internally in the engine as you cannot compress water.

 

[Mike63]

Thanks. I don't know for sure the plug was wet, just the idle was rougher than usual after starting. I have watched an engine break from a hydralic lock on a Focus that went through a water ford too fast, fortunately I was not driving! Turned out a conrod broke.

The car works fine after it is filled and bled, I can drive it in town or on motorway without symptoms. It's the trip after that during which it overheats.

At least spares are good value! Head gasket alone, not kit, for my Honda Accord was £80.

 

[midget4hire]

I had a similar thing with my old mk2

it went from head gasket to then being a problem with the injectors
one of them had cracked and a piece had managed to get into one of teh cylinders
maybe not the same thing but thought i might aswell mention it

 

[Mike63]

It's starting to become apparent why the second hand Fiat one can buy is 2/3rds the age and 30k fewer miles than the equivalent Fiesta. No offence meant, I knew this when I bought the car and it has some very good points, cheaper to run, economical, more space, younger, less wear...

Next trial on the overheating front is an attempt at a temporary repair with radseal. Helpful shop Dunlops in Shettleston had a range to choose from, usual bars leaks and radseal @ £4 ish, moving up to a 'popular with the trade' professional/heavy duty block repair at £8, then one claiming also head gaskets at £12, K-seal (has website). Full of bells n whistles microfibres, I figured if anything works...

But it didn't. Annoying because I put the thermostat back and antifreeze with the hope that it might get me home. These sealants rely on the pressure differential between the point of leak and atmospheric, basically goup in the fluid that jams in the hole as the water gushes out, so one expects some fluid loss whilst the system heats up and pressurizes. So perhaps the gap is bigger than the 0.75mm it claims to seal, or the gasket is failing so fast it can't keep up, or (my favorite) the hole is from the chamber to the water passage so the pressure gradient changing each power stroke keeps the goup from jamming.

The biggest problem appears to be the rapid onset of vapourlock that blocks circulation in the cabin heater circuit (which includes the cylinder head) after which the car overheats and boils. Fragile design perhaps, and indicated by the bleed point at cylinder head height, asking for trouble IMO.

During a 20 mile drive yesterday I boiled half a dozen times and can now advise you folks on the best way to limp home your overheating puta, I mean Punto
1) Turning off at stops/lights doesn't appear to help, because I think any boiling leads to airlock.
2) Use the cabin heater to keep boiling down and give prior warning. Full fan and max heat lets you drive further. Also when heat no longer comes out, circulation has stopped and you will boil in a couple of minutes, unless you can re-establish cabin heating. High revs 4000+ can sometimes recover circulation in the cabin heater.
3) Hold the revs at 2000 at each stop, which keeps the circulation pressure up through the engine so the cabin heater can continue to cool the engine.
4) Use 1st or 2nd gear in town to keep the revs up, 3000+
5) When this finally fails, the cabin heat stops heating. Then the needle moves into the 4th quarter red area. Stop now to avoid disaster.
6) The Achillies heel bleed valve is now your friend. Most cars, you loosen the main filler bottle cap, a small Mt. Vesuvius occurs, all your coolant is now on the tarmac and the engine is still stinking hot. Instead, open the bleed valve, whilst wearing a glove, and it vents the steam slowly. Eventually the pressure lowers enough for water to get back in and cool the metal engine parts. Maybe 5 mins. At this point or a bit earlier you can open the radiator bleed valve, which will also be venting steam not coolant.
7) When the venting has just about stopped, loosen the main cap of the overflow tank. If the water rises then you need to let it cool more. If the water siphons back into the radiator then it is now cool enough to refill. About 10 mins. I was using about 2l of water.
8) Fill up in the normal way, first until the radiator bleed vents water, close that, then the heater pipe vents water. Because it's hot there will be bubbles n froth beforehand. The car needs to be level to nose up for this.

 

[Georgina]

Sounds horribly familiar...
A few months ago my car wouldnt start for no reason, I eventually got it to start after several attempts, and it felt very juddery while idle. This seemed to be a one off so I ignored it.
I'm not sure if it was before/after this that my car started overheating occassionally, especially on hot days. I would sometimes be putting in a litre of water a day, basically before each (short) journey. In an attempt to prevent overheating I started having my heaters on full blast all the time, this did help somewhat.
Since then the thermostat light has come on a few times, usually going off again pretty quickly. Although the car has been very temperamental, being fine for a while, then suddenly playing up big time, then being fine again the next day.
There have been a couple of occassions where the car hasnt started, just wouldn't turn over.. replaced the battery about a month ago, thinking this was the solution.. the car was a bit dodgy to start to begin with, but fine again after a day or so.
Then at the beginning of July it had another off day.. took a few attempts to start, then when my brother was taking me to the airport (bad timing) the warning light came on again.
I was away for a week, car has been fine until 2 nights ago.. Took several attempts to start, felt very juddery and rough to drive, engine management light flickered but didn't come on properly.. so the next day (yesterday) I took it to the garage. The verdict was that the head gasket is blown, which is what we suspected.. they quoted me £500. Took the car away as I may be able to get it fixed my a mate on the cheap. Anyway, giving my boyfriend a lift home last night (yes I know, stupid to drive it but I had no choice), the car started fine, felt a bit rough.. then on my way home (didn't stop, just dropped him off and carried on as I didn't want to turn the engine off in case it wouldn't start again!) the warning light for the temperature came on.. I was nearly home so hoped to get back before it overheated altogether.. Unfortunately this didn't happen..! Within about a minute of the light coming on the car lost power, wouldn't start back up. I sat there for a minute or so, and then just about got it to start, so crawled over to a bus stop as I was in the middle of the road. After spending some time on the phone to my brother trying to figure out what to do, the car wouldn't start again, so got a lift home with some (very) kind people who noticed me being alone in a broken down car late at night. Phoned my insurance company, arranged recovery and drove back down to where my car was in my mum's car.
My car is now out the back of my house, and I do not intend to drive it until it is fixed, I'm now very worried I may have done more damage last night..
So, I'm afraid.. as this all sounds so familiar, I think there's a pretty good chance it's your head gasket... Sorry to say it..! The guy at the garage (who my family use a lot) said that the head gasket being blown would cause difficulty to start, overheating, and juddering.
If you go to a website called shop4parts you can find head gasket sets pretty cheap.

 

[Mike63]

Thanks for the comments. shop4parts seems like a good link, fair prices.

Head gasket sets on ebay are under £30, it's the labour as you discovered. However I figure I could do it in 8 hours so @£25/hr it should be £200 labour. Fiat price for the headgasket set is £70, plus antifreeze say £10, since there's possibly water in the oil there should also be oil and filter in the budget, say another £30 from a garage. So I think it's a £300 job. First three garages did not agree

However all garages did require the head to skimmed, which should be £30-40. If I did the job I would measure it instead since I have not really overheated the car. Not a difficult job, straight steel ruler edge down and check underneath with feeler guages. Part of this assertion comes from the fact that the temp warning light flashed on only briefly and only once when the problem first occurred. I'm of the opinion that a warning light should come on *before* it boils, not after! What have other people found? Also, is the temp sensor in the heater pipe behind the only one on the engine? It seems to control the gauge, the light and the fan. Curiously, if unplugged the fan does *not* come on, which seems like bad failure management to me.

In my case I took the plugs out, which were new 8k/8months ago, and there was a slight pink colour to the ceramic of #4 compared to the other 3. I'll post pics if I can. I put this down to a possible, just possible, colouration from the copper in the radseal. Certainly not clear cut.

Sadly without my tools or cover I had to give it to a garage. They tried some stuff and in the end agreed with me on headgasket. One test, which I think is a good tip:

Garage claims that the overflow tank vents exhaust smelling gas via regular bubbles. Good test that I did not think of, which I guess involves leaving the cap off as the car warms up from cold.

Anyway they took the head off and there is maybe a 5mm stretch of the fire ring around #4 that has carbon deposits to the outside edge. This is just in the direction of the water passage. Pretty marginal failure, but not gas tight so that's enough.

Garage will fit new cambelt, alternator belt I provided as this is zero extra effort. I got a new water pump too as this is a 5 mins job when the rest is removed.

 

[Georgina]

Glad you've got it sorted.. my car is currently sat out the back of my house awaiting repair while I find out if my brother's mate can sort it for me.
Also, I hope that light does come on before the car overheats, cos that's lame if not, you get no warning.

 

[richie.guy]

Also, I hope that light does come on before the car overheats, cos that's lame if not, you get no warning.

It's already too late 9 times out of 10 if you see that light, which is why I always reccomend people get the higher spec dials with rev counter and water temp. That way you can see any airlocks in the system before it overheats (it will fluctuate) and as soon as it goes over half way you can kill the engine before any damage is done, if you're quick.

Most of the time the car overheating is due to the owners' poor maintenance of the car.

 

[Mike63]

I'd be most interested in your theory as to how poor maintenance causes the fire ring in the headgasket of the far water hole in the corner of #4 cylinder to start leaking gas pressure. That's not how heads warp in my experience - right by the furthest head bolt. That this site has pages and pages on headgaskets makes me think its an engine weak point.

Replace head gasket is not in the maintenance schedule, nor thermostat, nor radiator, so if they fail is that really poor owner maintenance? If it boils because the fluid is low, and the regular service was skipped, then fair enough. If the radiator corrodes and there's no antifreeze, then fair enough. But if the fluid is low because the radiator corroded in-spite of antifreeze, is that a maintenance issue or a design issue?

The next point: if 9/10 times when the light goes on the engine is broken, then that's surely a design flaw?? Can't blame the user for that! The point of the warning light is supposed to be just that, a warning. We know the temp gauge hides the real temp and I understand why. My complaint is I picked up the overheating because I heard knock, the guage was at 75% and no warning light was on. I think that's poor engineering and I put it down to
1) a circulation prone to fail through airlock, and
2) the temp sensor being in the location that gets the airlock.

Also most engines can boil without failing. My aluminium Honda engine puts out twice the power with 2/3 the engine size and a radiator 30cm x 20cm, can boil over, guage in the red, no damage done. My Sierra pinto could drive indefinitely on just convection cooling. My Mini boiled it's oil, still no headgasket failure.

Then we have to look at how easy it boils. Talk to the Ford dealer and he will call the overflow bottle a 'degas' bottle. On a punto, it's overflow only because it's at a price on the side of the radiator rather than in the circulation path at the highest point. Result? a) difficult to bleed, b) boils easily. Design or maintenance problem?

In fact, maybe that's the answer: a high level de-gas bottle in the heater circuit. Won't fix the light though.

 

[richie.guy]

Euro 2 HGT's had the 'de-gas' bottle and it was then removed on Euro 3's as there was no requirement for it in Fiat's eyes.

Some people are unlucky, but punto's are cheap cars and most of the time (not all of the time) the owners are on a tight budget and don't spend money on things they should, like the things you listed!

The HG's are a weak point on these engines but most people don't experience problems if they are looked after. Granted you shouldn't have to baby the engine as much as you do, but if it saves doing the headgasket then so be it.

Agree 100% on the light issue and the inherant PITA cooling system on the smaller engined punto's. They are a pain the bleed and they aren't the best design in the world, but it doesn't mean that people shouldn't look after them correctly and be aware of the problems.

 

[Mike63]

Credit to you Mr. Richie! I agree with your comments.

In fact the more I think about it, the more I think a degas will help. There's a nice spot between the battery and the bulkhead, above the engine level, and that pipe with the bleed would do nicely as the circuit to tap into. Next time I'm at the breakers I will have a look for some suitable donor. It should make the system easy to fill and would ensure that the sensor stays immersed so the guage reading would be more reliable. The engine would be more robust to a minor headgasket leak because it could vent gas instead of pushing the water out. Hopefully then no head warping. I think the radiator cap would need sealing.

Fixing the light seems more of a problem because I think it will all be on one PCB in the cluster, so the only easy path is to modify the resistor response. We can't just put a parallel resistor of the guage won't read cold. We could add a parallel temp sender with a series variable resistor, but then we'd have to plumb it in somehow. As a long shot, is there a physically compatible Fiat temp sensor but with lower resistance?

 

[Mike63]

Well we're back and running, no overheating, but something's still not quite right. Symptoms are:
1) The revs not only hang high sometimes, but also rise to about 3000 which I think must be idle valve fully open. This can happen when stationary or moving.
2) MIL light still on
3) Slightly rougher idle I think.
4) Possibly lower mpg, not many miles on it so far.

2) might be a red herring as it has not had enough time to clear perhaps.
3) might be due to slightly higher compression ratio after skimming. Maybe. Or it might have lost its self-trimming, I presume Fiat does that?

MoT was due so I know the emissions are right on the nose, hence front lambda OK and no misfires at idle. I'm thinking a connector to a sensor has failed so the ECU no longer knows 'something' eg: what gear, what speed. Any ideas people? Thanks.

 

[Mike63]

Revs hanging solved. Took the air filter off and the throttle cable was mis-routed and kinked, so didn't always fully return.

So we're left with MIL lamp on and I'm sure mpg is down. On the second problem I had a theory: exhaust manifold is not sealing well, so there's some air leaking in. This causes the lambda sensor to report lean, which causes the ECU to deliver rich fuelling.

I contacted the Fiat dealer to see if they could plug in their DTC reader. They wanted £77+vat to rundiagnostics on the car! So...
a) does this ECU report codes without a machine, often triggered by shorting the pins together and reported by MIL lamp flashes?
b) where is the OBD connector anyway?
c) anyone tried this:
http://www.elektor.com/products/kits-modules/kits/stand-alone-obd2-analyser-(070038-72).91476.lynkx
= build an OBD code reader for under the cost of the dealer.

 

[frankharrison]

OBD is in the fuse box on drivers side. Just under fuses.