Cause of over heating?

[what2do]

Yesterday at 9.30 am, the fan came on which was a bit of a surprise. I was in a traffic jam and the sun was shining but it wasn't warm enough to for the fan to come on when I compare it to all the times I've sat in traffic on the M25 in summer months without the fan cutting in. So, a bit of history, the van has always had a coolant leak and I just top it up with a 50:50 mix that I've always got in the van. I'm wondering if it's likely that as the coolant escapes, air is being drawn in and now sitting in the rad. I've not bled the van in a couple of years and have probably 'topped' up with about 6litres in that time. Easy enough to remedy if this is the case, I'll undo the rad nut a turn or two and see what escapes.

In addition to this, my LPG has never been set up properly and I recently 'found' the cause of a running problem that I'd had- turned out to be a rather loose spark plug. Thought I'd check the plug whilst I was at it - pale beige in colour, very dry and covered in 'crustacean' like snots around the electrode. All 4 plugs were the same so it's obvious that it is too rich, I need to sort this ASAP but I was wondering if this running rich would cause the engine to generate that much extra heat that it would cause the engine to overheat when stationary now that the weather is slightly warmer.

Penny for your thoughts, cheers.

[ghost123uk]

Thought I'd check the plug whilst I was at it - pale beige in colour, very dry and covered in 'crustacean' like snots around the electrode. All 4 plugs were the same so it's obvious that it is too rich,

Running rich won't cause overheating. Running lean will though. Whilst you cannot use the plugs colour as a mixture test when using LPG, I am worried by the "'crustacean' like snots around the electrode". That doesn't sound healthy and I am hoping it's not molten aluminium that has splattered onto the plug from severe lean overheating.

A close up pic would help a lot here.

Get that mixture checked right away, and drive it there like a baby. Any decent garage should be able to do it at least roughly correct as they all have exhaust gas analysers.

[ghost123uk]

Get that mixture checked right away, and drive it there like a baby. Any decent garage should be able to do it at least roughly correct as they all have exhaust gas analysers.

In case a garage who is not conversant with LPG settings needs the info, here are some facts and figures I have accumulated from various sources that they might find useful.

Normal CO readings. If the combustion process is succeeding at or near the stoichiometric point (AFR equals 14.7, Lambda equals 1.0), CO levels during an idle test will typically measure less than 2%.

Low CO readings. There is, effectively, no reading for CO that can be characterized as too low or "below optimal".

High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems.

High oxygen (O2) readings indicate too lean an air-fuel ratio.

O2 (Oxygen): A high O2 reading indicates a lean mixture or an exhaust leak.

Note: if O2 content is above 2 to 3 percent, air dilution of the exhaust gases being measured is indicated and the accuracy of the all of the gas readings may be negatively affected.

Test 02 sensor in air = 20.7%.

Low O2 indicates a rich fuel mixture.

High carbon dioxide (CO2) readings indicate a nearly ideal air-fuel ratio and efficient combustion.
.
Maximum is around 16%.

Lambda = higher the number = richer

The highest CO2 with CO and O2 with same low values and the lowest HC you can get and you have almost the perfect engine combustion..

This is of course assuming you know how to tweak the main "power valve" in the gas pipe. Don't touch the adjusters on the vap unit, that is definitely best left to a proper LPG place (E D I T = Jeez, Salisbury is a long way from both Campershack and Gasure )

[itchyfeet]

A small ammount of air will self bleed out
Whats happening on the pressure tank level?
Could be partially stuck stat or blown head seal

As for tuning the LPG I have been on at him to fit the lambda boss in the exhaust and guage for probably best part of a year now

[California Dreamin]

The other guys have pretty much covered it...I would just add my comments.

Lean can cause an engine to run hot, not rich, as John pointed out.
If the fan is coming on 'prematurely' then its not going to be air in the rad....air normally results in NON operation.
I am also intrigued as to the 'deposits' on the spark plugs...large crustaceans could be a few things, most likely carbon deposits due to burning a fair bit of oil (sign of a worn engine..rings or valve guides).

Martin

[what2do]

Right, where do I start? Forgive me for mixing my rich with lean.

Pressure tank is indeed full which is a blessing. The crustaceans are solids around the the base of the electrode, in the area of the ceramic. They too were very pale in colour and took some shifting. Will have a look at the plugs tomorrow and see if the solids have built up since I last cleaned them - last year, the van was run for several months with a half knackered vac/adv unit causing lumpiness and mis fires, would this manifest itself in solids on the plugs?

Didn't get to check the rad today but will do it in the morning once it's warm and will report back. I too have been thinking that after a few years of 'topping' up, there may be air in the rad, that's what I'm hoping for anyway!!!

[what2do]

Update; ran the van (on LPG) for approx 30 minutes on the drive today at midday'ish when the temp was pleasantly warm. It got 'hot', needle was at 12 o'clock and the fan cut in. Fan ran for a couple of minutes then off again for a short while until the van kicked in again, allowed this to happen for a few times before checking the rad. Undid the bleed nut and there was an immediate weeping which I allowed to run for a good minute (probably lost no more than an egg cup full of coolant). So, rad is functioning as it should, so too is the fan.

Whilst still running, switched over to petrol to see if the symptoms were the same. They were, fan on - fan off etc. for another 15 minutes.

Pressure tank was always full and I could see that whilst hot, the top up tank was full beyond the bottom of the cap.

What's next folks? Cheers.

[kevtherev]

That all sounds perfectly normal to me.

my LPG plugs are similar too.
No issues for several years

[ajsimmo]

Sounds like rad switch now cuts in at too low temp. Try a new one.
Air leak on vac unit may have caused lean running at low revs, and insufficient spark advance (Not necessarily anything to do with your symptoms - just sayin...). Btw, I hope the timing setting wasn't advanced by someone to compensate for a dodgy vac unit. I see this a lot!

[what2do]

Sounds like rad switch now cuts in at too low temp. Try a new one.
Air leak on vac unit may have caused lean running at low revs, and insufficient spark advance (Not necessarily anything to do with your symptoms - just sayin...). Btw, I hope the timing setting wasn't advanced by someone to compensate for a dodgy vac unit. I see this a lot!

.??? In the past when I've been bleeding or revving the van for what ever purpose, the fan normally comes on when the needle is at 12 o'clock, this has always been the way. The switch is about 3 years old, changed it when I bought the van along withe the thermostat, bought from BW.

Timing was set after the new vac/adv unit was changed.

Puzzled, more because it's not 'as it was', don't want to think that something terrible is on the horizon.

Thanks, thus far.

[what2do]

Get that mixture checked right away, and drive it there like a baby. Any decent garage should be able to do it at least roughly correct as they all have exhaust gas analysers.

In case a garage who is not conversant with LPG settings needs the info, here are some facts and figures I have accumulated from various sources that they might find useful.

Normal CO readings. If the combustion process is succeeding at or near the stoichiometric point (AFR equals 14.7, Lambda equals 1.0), CO levels during an idle test will typically measure less than 2%.

Low CO readings. There is, effectively, no reading for CO that can be characterized as too low or "below optimal".

High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems.

High oxygen (O2) readings indicate too lean an air-fuel ratio.

O2 (Oxygen): A high O2 reading indicates a lean mixture or an exhaust leak.

Note: if O2 content is above 2 to 3 percent, air dilution of the exhaust gases being measured is indicated and the accuracy of the all of the gas readings may be negatively affected.

Test 02 sensor in air = 20.7%.

Low O2 indicates a rich fuel mixture.

High carbon dioxide (CO2) readings indicate a nearly ideal air-fuel ratio and efficient combustion.
.
Maximum is around 16%.

Lambda = higher the number = richer

The highest CO2 with CO and O2 with same low values and the lowest HC you can get and you have almost the perfect engine combustion..

This is of course assuming you know how to tweak the main "power valve" in the gas pipe. Don't touch the adjusters on the vap unit, that is definitely best left to a proper LPG place (E D I T = Jeez, Salisbury is a long way from both Campershack and Gasure )

Forgot to say thanks - thanks John

[what2do]

That all sounds perfectly normal to me.

my LPG plugs are similar too.
No issues for several years

So, if your plugs are the same, what's the cause of the 'solids'? Any ideas?

[itchyfeet]

My guess is poor combustion caused by failed vac unit on dizzy, I say change plugs and see if it happens again.
Is it running right temp now or have you not given it a good run since?
Worth a 15 miniute compression check as you have the tester.
worth popping the stat out and boiling it in a pan (new oring required)

did I mention the lambda guage?

[kevtherev]

That all sounds perfectly normal to me.

my LPG plugs are similar too.
No issues for several years

So, if your plugs are the same, what's the cause of the 'solids'? Any ideas?

My guess is it's oil.
I occasionally top up the oil to the max, the engine then promptly returns it back to midway on the stick.
I think the oil mists and gets sucked into the crank breather.
I proved this recently and topped the oil up, then put it on a gas analyser, the HC results were at 1400 ppm
After a week the gas was analysed again it read 330ppm

[what2do]

That all sounds perfectly normal to me.

my LPG plugs are similar too.
No issues for several years

So, if your plugs are the same, what's the cause of the 'solids'? Any ideas?

My guess is it's oil.
I occasionally top up the oil to the max, the engine then promptly returns it back to midway on the stick.
I think the oil mists and gets sucked into the crank breather.
I proved this recently and topped the oil up, then put it on a gas analyser, the HC results were at 1400 ppm
After a week the gas was analysed again it read 330ppm

Interesting point, I often wonder if it's worth me constantly keeping the oil up to the max mark on the dip stick, probably not judging by your emission figures.