Hi. First time poster. Amateur mechanic out of depth. Punto 2000 1.2 8v. Recently overheated. Set about replacing head gasket. Took head to get it skimmed and was told that some marks on the mating side of the head were no longer present indicating that the head had been skimmed previously beyond tolerance. The marks (that I could not see) were described as being 4 in number and looked like punch marks in the head surface to indicate safe skimming depth.Decided to get it skimmed anyway and hope for the best. Replaced head and think I did everything right but first time doing it. Now when I turn key, engine cranks, doesn't fire and after a few cranks stops with a kind of a thud. It's hard to describe but it's doesn't sound mechanical (i.e. 2 things hitting each other) but more like air being compressed. Every now and again there's a single backfire. Assuming I've done the head replacement correctly (95% confidence), am I right in thinking that my issue is either the timing or the over-skimmed head? I've checked the timing twice and seems right but I'll check again. Any clues?
Technical Possible overskimmed head - Help...
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Technical Possible overskimmed head - Help...
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Sounds like the timing is 180 degs out or the plug leads are on wrong. Be careful backfiring (literally) can blow a hole in the inlet manifold.
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You can skim beyond the maximum skim level, however, the further you go, the more of your cambelt tensioner adjustment window disappears. Eventually, you have to adapt the cambelt drive since there is not enough adjustment on the tensioner to set the tension right.
All goes well though, you should have fantastic compression if you are beyond skimming limits.
All goes well though, you should have fantastic compression if you are beyond skimming limits.
suggest recheck timing; use the marks for TDC on the flywheel not the front cover; you may have to use higher octane fuel; reconditioned heads are not expensive and this may have been a better option..........
The marks your looking for are round cornered
squares holes approx 20mm x 20mm in the head
which are set away from the combustion chamber
and near the edges of the long side of the head.
John
squares holes approx 20mm x 20mm in the head
which are set away from the combustion chamber
and near the edges of the long side of the head.
John
Everybody, many thanks for the help. The not starting problem was because I had put the sprocket used by the TDC sensor on incorrectly. I came across the answer somewhere on this forum and realized I hadn't lined up the holes correctly. So although the crankshaft/camshaft were timed right I suppose the ECU got confused about when they were at TDC! Anyway, fixed that this morning and it started first time. So far so good. Now I have a different issue. The engine idles a little roughly. I followed the instructions in one of the guides and bled the cooling system. When I looked under the rocker cover I saw quite a bit of the creamy stuff that people associate with oil and water mixing. Also, the exhaust is very visible, sort of looks like steam and where it hits the rear bumper it forms water. So I'm now not sure if my gasket replacement worked OK or if what I'm seeing is due to the old oil which got water in it? The steam/white exhaust makes me wonder too along with the rough idle. Another thing I notice is that the radiator fan never seems to come on. I hooked the fan directly to the battery and it works fine. I also opened the engine fuse box and swapped the 30A relay(?) with the same one that seemed to be for the injectors to see if that was ok. The engine started as usual which made me think both relays(?) are ok. I say relay but am not sure if that is the right word. It's not a fuse but one of the larger plug-type-thing in the fuse box. There's a few others including the horn based on the schematic on the underside of the cover. Can someone explain how the fan gets switched on/off? I'm aware of the coolant sensor which is green and is behind the coils but am not understanding how the fan on/off decision is made. There are only 2 wires from the fan - one is earthed and the other goes to the fuse box so there seems to be no temp decisionmaker at the fan end. Any advice on testing the fan on/off decision making would be great! One last piece of info is that when I turn the key so that the ignition lights come on, the temp warning light comes on as it should and then goes off when the engine starts. Is that proof that the coolant sensor is working ok? Anyway, that's where I'm at. Thanks again.
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Year 2000 Punto will switch on the fan via the ECU, based on its measurement of the engine coolant temperature sensor. The rough idling, steam from the exhaust and cream under the oil filler cap could be remnants of the previous fault not out of the system yet. Did you renew the oil, filter and coolant when you did the work?
I flushed the cooling system but was holding off changing the oil thinking that the old oil would be ok until I was sure the head gasket renewal had worked. Perhaps foolishly trying to not spend money unnecessarily as I wasn't sure if the overskimmed head would work out. Today I got an oil filter and oil and will change it tomorrow. I was wondering if I should go to the trouble of removing the sump to give it a good clean? In case I need to replace the bloomin' gasket again, a couple of questions. A local scrapyard is selling a head for 100 euro (roughly 87 british quid). Would people think this is the way to go or to look around for a re-conditioned head? and if so what should I expect to pay for recon? Hopefully this is moot and the work I did is good.
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Just wanted to give a quick update and have a few more questions.
Haven't had a chance to change the oil yet. Today I flushed the cooling system based on the guide(s) in this forum. Very useful. I also added a bottle of radflush. What came out was a little brown but didn't look too bad.
I also took off the coolant sensor and again it seemed ok. Had a little brown coating on it but it wiped off.
It's starts fine but the idling is still a bit off. The white steam from the exhaust is a lot better. Still get a bit but a lot less.
Took it for a 10 minute spin. Went ok at first but then started losing power. No lights on dash (by the way I only have a temp light, not a gauge). Stopped the car and popped the bonnet. Everything looked ok but the hoses and the radiator were pretty hot. My fan just doesn't want to come on ever! Tried the heater and got hot air. Spent a lot of time bleeding the cooling and am fairly sure I got the air out.
Any ideas on why the idle is bad and the loss of power? If my timing was off by a notch would that explain it? Thanks for the info on how the fan on/off decision is made. If the ECU is trying to turn the fan on is there any way I can determine that? Do the control wires from the ECU go to the fan relay in the engine fuse box? If so could I hook up a meter to them to see if the ECU is trying? If my coolant sensor was bad, am I right to assume that would should up on the dash as engine warning light? Any guidance on how to nail down why the fan isn't coming on would be very helpful.
Monday I plan on checking the timing again, changing the oil and wiring up the fan to run constant. Hopefully that will eliminate some unknowns.
One last one. I am still using the old spark plugs which were there when it overheated. Could they be damaged in some way? Should I change them too? (by the time I'm finished I'll practically have a new engine!)
Thanks again folks. The help is extremely useful.
Haven't had a chance to change the oil yet. Today I flushed the cooling system based on the guide(s) in this forum. Very useful. I also added a bottle of radflush. What came out was a little brown but didn't look too bad.
I also took off the coolant sensor and again it seemed ok. Had a little brown coating on it but it wiped off.
It's starts fine but the idling is still a bit off. The white steam from the exhaust is a lot better. Still get a bit but a lot less.
Took it for a 10 minute spin. Went ok at first but then started losing power. No lights on dash (by the way I only have a temp light, not a gauge). Stopped the car and popped the bonnet. Everything looked ok but the hoses and the radiator were pretty hot. My fan just doesn't want to come on ever! Tried the heater and got hot air. Spent a lot of time bleeding the cooling and am fairly sure I got the air out.
Any ideas on why the idle is bad and the loss of power? If my timing was off by a notch would that explain it? Thanks for the info on how the fan on/off decision is made. If the ECU is trying to turn the fan on is there any way I can determine that? Do the control wires from the ECU go to the fan relay in the engine fuse box? If so could I hook up a meter to them to see if the ECU is trying? If my coolant sensor was bad, am I right to assume that would should up on the dash as engine warning light? Any guidance on how to nail down why the fan isn't coming on would be very helpful.
Monday I plan on checking the timing again, changing the oil and wiring up the fan to run constant. Hopefully that will eliminate some unknowns.
One last one. I am still using the old spark plugs which were there when it overheated. Could they be damaged in some way? Should I change them too? (by the time I'm finished I'll practically have a new engine!)
Thanks again folks. The help is extremely useful.
ALWAYS change the oil when head gasket fails; oil will be contaminated with water and bits of crap can get in to the oil holes during the HG change; change it and filter now and again after 100 miles or so; the spark plugs will be water damaged and may account for rough idle; glad to hear you are making progress; if car then goes ok just wait and see before buying another head; sorry forgot to suggest tdc sensor as forgot to replace mine when I first did a punto HG change and wondered why it wouldn't start........
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Avoid driving until you get the cooling system sorted.
Is the thermostat opening? If in doubt fit a new one.
Are you 100% sure coolant is bled properly? Loosen hoses at the highest point as well as opening bleed valves.
Is the water pump OK?
Is the thermostat opening? If in doubt fit a new one.
Are you 100% sure coolant is bled properly? Loosen hoses at the highest point as well as opening bleed valves.
Is the water pump OK?
Thanks WhiteSei. I have fitted a new fiat-original thermostat. When I took off the old one I saw that it was not closing properly. I watched what happened to it in a pan of water that I brought to the boil. It did open a bit, didn't close fully when cool and clearly wasn't working right so I replaced it. I'm 98% sure I have bled the coolant properly. I know the hot coolant is going thru the radiator as I can feel the top hose get hot when the engine warms up. But as I say the fan never seems to turn on. The fan motor is good as is the relay (see previous post) so the only thing I can think of is that the coolant sensor is not working right. But this confuses me as I would have thought that if the ECU decided the sensor was bad it would turn on the engine warning light on the dash and this is not the case. Also the temp warning light comes on pre-ignition as expected which again, I assume (need help here) is an indication that the temp sensor is working as expected by the ECU. I took off the water pump to check it and it seems to be fine. So I put it back on. I put radflush into the coolant yesterday to give it a good flush. As the engine idled with the radflush in I thought I noticed a kind of a sweet smell from the exhaust. I have read that antifreeze burning in the combustion chamber produces a sweet smell and I am wondering if radflush would do the same. If so, I may have the head gasket leaking again or even worse a crack in the head and/or the block as somehow the coolant is getting burnt. Anyway, sorry for the long messages but that's where I'm at. I'll persevere for the time being although I have to say despair is coming up the driveway....
worth fitting a temperature gauge; at least you would know whether engine is really overheating; the fan only usually comes when the car is stationary and engine has been running for some time
I was thinking of doing exactly that today tinytim. I'm now wondering at what temperature the fan should kick in? I'll try testing the coolant sensor as well. Depending on replacement cost I might put an new one in just to be sure.
there are 2 coolant sensors; one for the warning light and one for the fan/ecu; they are expensive so avoid replacing unless you are sure they are faulty; a temperature gauge kit comes with a sensor that replaces the warning light sensor anyway but you may need an adaptor....
Quick update: Last night I discovered the wiring diagrams in the haynes manual. According to haynes my punto (1.2 mk2 8v) only has one coolant sensor (green one beside inlet manifold) and the output from the sensor controls how the ECU turns both the fan and the temp warning light on/off. But at least now I can identify the wires that go from the ECU to the fan relay so I can test if the ECU is trying to turn the fan or not. Haynes also says that the ECU works with the coolant sensor by setting a voltage across it and watching the varying current that comes from it as the resistance of the sensor increases as the temp rises. So I should be able to test the sensor with a meter. Rain expected here soon which may slow down my outside work.
Me again. Today I replaced the oil and the oil filter. When I took off the rocker cover I saw a new layer of white cream on the inside top of it. I wiped it clean, replaced oil and filter and haven't looked since so not sure if water is still mixing with oil or if it was a residue from old contaminated oil. I also checked the timing and it looks about as exact as it can be. I then connected a meter to the wires of the coolant sensor. Started the engine. When I attempted to read the current a strange thing happened. The fan came on! Every time I tried with the meter set to read current it would cause the fan to come on. Stopped engine, removed sensor. Ohm reading of sensor was about 3k which is about right according to haynes. But I'm not sure the sensor is working right. I put the sensor back in but didn't connect it. Started engine. After a few seconds, engine warning light came on as did temp warning light BUT engine idled much better and fan on continuously. Took it for a short spin and it drove well. If I put my hand at tailpipe, small spatterings of water sputter onto my hand but the white exhaust is no longer there. Will try to get a new sensor and fit it. Will also fit a temp gauge.
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Every litre of petrol burns to CO2 and about 1 litre of water.
A voltmeter has a very high resistance so is effectively open circuit.
An ammeter has a very low resistance so is effectively closed (or short) circuit.
The light coming on shows that the sensor has a high resistance when its hot. So a faulty high resistance connection can make the ECU *think* the engine is too hot.
Crimp on a new connector and see if that solves the issue.
A voltmeter has a very high resistance so is effectively open circuit.
An ammeter has a very low resistance so is effectively closed (or short) circuit.
The light coming on shows that the sensor has a high resistance when its hot. So a faulty high resistance connection can make the ECU *think* the engine is too hot.
Crimp on a new connector and see if that solves the issue.
