overheating,no guts, misfire when hot?

G

granville1971

New Member
Hi There everyone.
Have commer pb . 1725 (iron head). electronic distributer. weber downdraft carb (1 year old)

Van has started to lose power.
No Guts.
Horrid misfire.
Plugs pretty clean and uniform.
Real dead spot on acceleration (which is hard to shake off)
Runs hot.
Has overheated after a mountain climb.
Ideas anyone?

Runs much better when cold
Runs awful when hot

Not that familiar with commers.
Head gasket?
Do they blow head gaskets easily?

No oil in water
No water in oil

Is the only real way to find out with compression test?
Or could it be something else?
Thanks very much everyone
 
Hi Granville and welcome to the madhouse:D
Is it chucking water out everywhere? if not then probably not head gasket but a compression test wouldn't do any harm. It sounds like it's running super lean, do things improve if you run on choke? Check for anything loose on the inlet manifold, make sure the vac line to the dizzy is intact and in place, make sure the carb is tight on the manifold. Also check the air filter, could be badly blocked. Commers are very simple with no real differences to any other old car, just that some things a re a little awkward to get at.
A few things to keep you busy;)
 
Panky said:
Hi Granville and welcome to the madhouse:D
Is it chucking water out everywhere? if not then probably not head gasket but a compression test wouldn't do any harm. It sounds like it's running super lean, do things improve if you run on choke? Check for anything loose on the inlet manifold, make sure the vac line to the dizzy is intact and in place, make sure the carb is tight on the manifold. Also check the air filter, could be badly blocked. Commers are very simple with no real differences to any other old car, just that some things a re a little awkward to get at.
A few things to keep you busy;)
Click to expand...

Hi Panky, thanks v much for reply and I feel very at home in this particular madhouse. Thanks v much.

My van: It had chucked water out, but that was due to the cooling fan not working (converted to electric fan ages ago).
Fixed now. And a lot cooler now. (My initial thoughts were that I damaged the gasket when it initially overheated (miles from home) but your good advice has questioned this).

But still running rough when warm: it idles fine but just has no power and starts missing horribly under load.
Lean mix?: Will try a drive with the choke out. And could I have burned the valve seats?
It almost stalls under load. In fact, when accelerating it sometimes does.

Also I've noticed that it "runs on" a bit after ignition off. Backfire sometimes too.
Could it be timing? I timed it at 10degrees btdc.

Your advice over lean mix is good. Esp inlet manifold. I once had a sunbeam with this issue (30 years ago).

Thanks very much indeed.
 
Hopefully it will be as simple as that, but don't mess with the timing it doesn't usually move - unless the dizzy clamp is loose:eek:
Did the rough running start straight after the overheating issue?
 
10 deg is max, try 6 deg with modern fuel. Have you checked the tappets, could be leaving valves open when hot. Should be 12 and 14 thou when hot. Otherwise, as Panky says lean mix and possibly air leak.
 
Panky said:
Hopefully it will be as simple as that, but don't mess with the timing it doesn't usually move - unless the dizzy clamp is loose:eek:
Did the rough running start straight after the overheating issue?
Click to expand...

Hi Panky,
Sorry for late reply. Big drive.
Thanks for your ideas.
The rough running is getting incrementally worse.
When I collected the van (its new to me), I drove down from Berwick to Bristol via london (500miles). Very fast van, rather took me by surprise. Only first overheated in London. Having the heater on helped. But it did throw out the water several times. I realised pretty quick that the fan wasn't working and that the engine was being cooled by my forward speed alone. But I did notice that, when the engine was getting hot, there was a bit of a dead spot on acceleration.
The dead spot is seemingly getting incrementally much bigger. And now I can't leave home, due to the rough running (we live on a hill).

The spark plugs are all of consistent colour and indicate a slightly lean mix. An air leak on the inlet manifold, next to the block: would that affect the plugs next to the leak more? And create a more differing variety of patinas on the plugs?
Unless the leak is at the carb-manifold joint?

Thanks very much

Granville
 
martin maltas said:
10 deg is max, try 6 deg with modern fuel. Have you checked the tappets, could be leaving valves open when hot. Should be 12 and 14 thou when hot. Otherwise, as Panky says lean mix and possibly air leak.
Click to expand...

Hi martin, I think you guys are the closest, with the air leak theory.
Thank you for the thoughts.
Will check tappets etc tomorrow.
Many moons ago when I had a sunbeam (1725cc) , an old mechanic advised me to always do tappets with engine hot at the operating temp. Seemed logical.
I'll check tomorrow. and maybe advance the ignition a touch too.

Thanks very much

granville
 
Yep, it's recommended that the valve clearances are done hot on Rootes engines.
 
can check for leaks using EasyStart around the inlet manifold just watch the exhaust manifold - wear a hat and wet ya eyebrows :)
 
A curious occurrence I had many years ago was rapid wear of the heal on the points caused by a lack of lubrication on the distributer cam. This caused the points to close up on a long journey, with resulting slow rough running and very hot engine.
 
Maybe vaporisation of fuel or coil worth checking, coils get worse as get hotter if on way out, wouldn't explain overheating though but an air leak would be crap anytime not just hot
 
renaultvation said:
A curious occurrence I had many years ago was rapid wear of the heal on the points caused by a lack of lubrication on the distributer cam. This caused the points to close up on a long journey, with resulting slow rough running and very hot engine.
Click to expand...
Had similar symptoms on my old Frogeye caused by points closing. But this Commer has an electronic dizzy so presumably no points?
 
bazzateer said:
Had similar symptoms on my old Frogeye caused by points closing. But this Commer has an electronic dizzy so presumably no points?
Click to expand...
Hi Everyone.
Thanks for all your splendid input. What a brilliant lot you are.
Tomorrow, i'm going to check out manifold seals, timing, coil, fuel lines, ignition stuff, and finally
compression.

Do I put a new inlet manifold seal on dry? and how tight?

Also: Does anyone know what a good compression reading should be on the 1725 cc engine (Ib/in2). Iron c head.
How many turns of the engine? etc
Thanks again to all
 
Manifold gaskets go on dry but check the face is flat- there can be a big difference between the exhaust and inlet sides, a smear of grease on the carb to manifold wouldn't do any harm and save it sticking next time:) The bolts should be good and tight but be sensible as the studs aren't that big.
I did a compression test and they were all just above 150 psi warm and dry and the engine is strong with no smoke. Hopefully they should all be pretty even and above this. Give the engine a good cranking with all plugs out and throttle wide open - once you've got a dry reading put a couple of squirts of oil down the bores and see if it makes a difference.
Hopefully you haven't bought one of the cheap compression testers off eBay - they're a bit crap:(
 
Hi Panky,
Thanks for the advice.
have never done a compression test before.
Evenness is what i'm looking for it seems.
have been given an old british crypton set.
Will surely let you know how it goes.
thanks very much indeed
 
I fitted a new distributor from accuspark, less than £70 and no points or condenser to worry about, simple to fit. Red wire to + on coil black to - on coil, set the timing and that's it.
 
Panky said:
Any luck Granville
Click to expand...

Hi Panky, and all those other splendid souls who gave advice.
A massive thanks for all the help.
Sorry for being ages in responding with my findings.
Work weld work weld….

Here we go. did a compression test (worried about head gasket):
pistons ranged from about 152psi to 158psi (pretty good id say)
With oil in the bores, all were dead on 160psi. So head gasket is OK.

Everyone mentioned that the old girl sounded like she was running lean (air leaks).
You were all spot on. Took manifolds off and they were WAY OFF.
Carb joints bad too.
All skimmed and back on.
Runs way, way smoother.

On the overheating thing.
Not the timing.
But I'm guessing a stuck thermostat (so there's no water circulation).

The rad has an electric fan (converted in the 70's, and runs of a switch on the dash)!
And there are 2 mini rads for the interior heaters (blowers left and rt).

When running temp flies up.
Turn on heaters (both) and the temp dial flies down.
Turn on the main (rad) fan, there's not a blind bit of difference, showing on the temp dial, and overheats pretty quickly.
Water seemingly isn't making it to the main rad. Is getting to the heater unit though (so i assume that the water pump is ok)

Question- the 2 thermo housing bolts completely solid. I presume never undone before. Any tips? terrified of snapping them.
I'm so close.
Has anyone dismembered a thermostat through the waterway? and just left it permanently open?
Or is there a tip for undoing the pesky nuts?

Thanks all,
Granville
 
Housing bolts tend to corrode (ally against steel) and can be difficult. Softly softly approach, but they do snap off!
 
Excellent good work:)
Has it always been like this or just recently? Does the top hose of the main rad get hot? and can you see any agitation in the water as you rev the engine while its warm? If yes then the rad could be partially blocked:( If no then it could be the thermostat as you suspect. I'm also thinking if the two heater rads could be robbing the flow from the main rad, try closing the heater tap off and see what happens.
The thermostat bolts can be a pain so get plenty of release oil on the bolts, not WD40 some proper stuff, and repeat for a few days. You just have to bite the bullet I'm afraid, try tightening a little before un-doing - that sometimes works and maybe a little localised heat. When you eventually replace the thermostat cover be very careful as they easily crack as you tighten them down, don't use a cork gasket as these compress and make snapping the cover even easier. Check the faces for flatness and use a paper gasket with a little sealant and just nipped up should be fine.
 
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