General 900t overheating issues again

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General 900t overheating issues again

Hi Charlie
Your suggestions are more than welcome. I'm not a mechanic but I know my way around a Haynes manual. Basically, if it comes apart I'm happy to have a go... my first car was a Hillman Imp and there are a lot of similarities between that and the 900T mechanicals. The only real difference is 40 years elapsed time between the ownership of the two vehicles and its much more difficult to get parts now.

I've just checked the plugs and these are spot on for normal running, so I'm assuming the fuel mix is set up okay.

I've a second 9" electric fan on its way. I'll be fitting this behind the louvres on the radiator side, set to suck air in.

The fan controller I have can control two fans with the second one kicking in 10C higher than the first - its currently set at 90C which is about 3/4 of the way up the heater gauge. My thinking is to set the new fan (behind the louvres) as Fan 1 to kick in at 80C, this will suck cooler air in which in turn will be blown through the rad by the existing engine driven fan.

The current electric fan attached to the radiator under the cowling will be Fan 2 and should kick in at 90C as it does now. However, I'm hoping that with cooler air being sucked in from the outside fan 2 will rarely kick in, fingers crossed.

I'll report back once set up.
 
Hi Guys.

reading through the lengthy process so far i would consider setting both fans 10 degrees lower than you currently have them so 70c and 80c.


Our 900t runs with std rad and generally is good enough with our coupe engine and 900t carb set up although it was working well with an a112 1050 and saloon gearbox all off the std rad for a few months,

some really old thermostats used to have a small bypass hole 5mm or so in them to allow overall water flow even with the stat shut, this does allow the hot water to get to the stat and begin to open in advance, could be worth adding a small bypass hole,

is the heater matrix getting as warm as the rest of the engine,

annother thing that ive spotted before, if you take the water pump off at some point please check the water vanes are pushing the water into the engine block as ive seen the pump shaft from a clockwise engine in an anti clockwise water pump, (you can only see this by looking up the full length of the pump from the 4 bolt end).

hope this helps

Tim
 
With what seems like a large heat build up in the engine bay compared to coupes/spiders and yours having no hot air exit points, is there a way of propping the engine lid open by about 15mm at the top just to let out the excess heat/energy. its a shame the hinges are welded to the lower engine support as this would be a good place to be able to move the hinges slightly.

Tim

ps maybe even heat wrap the exhaust
 
Hi All

can i ask if its possible to post on here a photo of the underside of the radiator cap and post the dimension between the top of the cap and the rubber seal.

was it replaced at some point or is it one youve had on for while.

Thanks

Tim
 
Hi Tim
Thanks for the extra suggestions in answer to them.

  • The second electric fan arrived yesterday, I'll be fitting it this weekend and then play around with the temperature settings.
  • The heater matrix is certainly getting too hot to touch, so I think that's okay.
  • The thermostat and water pump are as they were when the van was previously on the road, I had her on the road for three years before mothballing her. Back then she was fine on a steady run (even motorway speeds) but over-heated when stuck in traffic or heavy load and if you had to pull in to refuel after driving for 100+ miles you had to wait 15 minutes with the engine cover open before she would restart. I think this was largely due to vapour lock in the fuel system. I've fitted an electric pump now which I hope will solve this - not had chance to test this yet but it certainly stops having to crank for ages to get the fuel through when she has been idle for a few days.
  • I took the van for a short run without the engine cover on and although still running hotter than I'd like the temperature gauge settled around 3/4 and without the need to have the cabin heater on. If the extra fan helps I'll see if I can get some louvres punched into the cover to aid heat loss.
  • The exhaust is heat wrapped - supplied by Frost.
  • I've fitted a new 900T radiator cap in the last few weeks. The one originally fitted was an old Unipart one with perished rubber seal. Water would escape from it and not flow into the expansion tank - it now does.
The only difference to the engine set up to the one before she was mothballed are the 4-branch exhaust, electric fuel pump, K&N air filter (no room to fit the old dustbin filter above the 4-branch exhaust) and 123-Electronic ignition conversion.

As noted, I knew she ran hot when stuck in traffic/under heavy load before but hadn't expected matters to get worse :confused:
 
Hi Gary.

Just check the rad cap you've just fitted is about 33/34mm height, this is important so the seals meet. There should be two rubber seals on the 850/900t cap system, so check your cap has both. Some cap manufacturers list the wrong types for the 850 so put a picture here if you want me to check.
In fairness the original system ran the fan full time so you may have to expect the electric fan to run full time too.

Tim
 
Hi Tim

Rad cap was as you described it, although forgot to take a photo.

9" Electric fan now fitted behind the offside louvres. There was very little clearance to get it into position due to having to get past wheel arc (forgot that bit when measuring up :bang:) - don't fancy my chances if I have to remove it. Fan is currently secured with cable ties, similar to how the fan would attach to the radiator. I'll use bolts eventually once I've managed to get hold of some bigger washers to fit over the louvre vents.

Took Connie out for a run approx. 45 minutes/20 miles.

Much improved but not perfect.

After a bit of mixed running, generally 30 to 50mph, the temperature gauge settled at 3/4. Still hotter than I'd like but when idling the gauge quickly comes back down to half-way (at which point the electric fans switch off).

The fans are set to kick in at 75C and with both fans running (along with the engine driven fan) the gauge settles at 3/4 when driving at 50mph. The readout from the 123-electronic ignition app reads a steady 95C dropping to 90C when idling and the gauge is half-way.

Incidentally, the 123 App shows 4,000rpm in 4th at 50mph. The 123-electronic ignition has a rev limiter at 6,000rpm. If my eardrums can take it, 60+ should be attainable - although once the interior is in and extra soundproofing added it should be much better on the noise front.

I suspect that there is still something not right with the cooling system. The extra fans are helping but delaying the inevitable strip down of all the cooling parts. I only really wanted to add an electric fan to help in traffic and heavy loads, not have to have them running all the time.

For now this will have to do as we are moving home in a few weeks and Connie should now be okay to drive the 60 odd miles to her new home. Then mothballed again while I work through the list of DIY jobs on our new home :(
 
I have literally this evening just finished installing an electric water pump and fan, I had a peice of ally machined to match the engine end of the original 4 stud water pump, once it comes of the block it finishes as a tube for a hose connecting to the elec pump, so far so good, I also upgraded to a more powerful alternator to handle the extra power. I have not driven it yet I just left it idling for ages and ages and it seemed ok, I will get some pictures once its tidied up and has had a good run out
 
Just on the off chance. Ate you certain the timing is correct(just querying incase the end pulley has done the wearing through the Keyway thing).

If you take out plug on 1 an carefully put a long screwdriver in there you can carefully feel when the piston is at tdc and check this corresponds to the marks on the pulley being tdc. Common 850 issue causing miss setting of the timing.

Tim
 
Hi Tim
When I first fired the engine up after refitting I set everything up to the timing marks, there was no play in any of the pulleys etc.(I also cleaned out the oil filter and there was nothing obvious out of sorts when refitting everything.)

From what I now understand I had everything set up at 0 degrees TDC.

However, when the garage did the pre-MOT I got them to check and adjust the timing and carburettor settings. They mentioned that the timing was out and should have been 8 degrees TDC/BTDC (not sure which way round he said).

I don't know where he got 8 degrees from. In the Haynes manual most engines are 10 degrees BTDC (static advance). In the supplement section there isn't a specific reference to the GF engine (as fitted) but for the North American Models it says the ignition timing should be 0 degrees TDC (static or idling).

Apart from the hot running the engine runs smoothly but I suppose the mechanic could have got the timing wrong - he wasn't a 'old Fiat' specialist (the one I used to use many years ago is now semi-retired and not easy to get hold of.)
 
Hi Powwow
Looking forward to seeing your electric water pump set up. In theory this should make maintenance and replacement much easier in the future - especially as most electric pumps are less than half the price of a standard water pump replacement.

Did you manage to get a bigger alternator off the shelf to fit? If yes, what was the make/model - the 65amp one I fitted some years ago (as unable to get a direct replacement at the time) took ages to find one with the same bolt pattern and then it had to machined to fit (to align the pulleys).
 
Hi Gary.

Most of my 850 engines are set at 10 degrees using a timing light at idle speed.

If you have a timing light you may wish to check you are getting an additional ignition advance of a further 28 degrees between idle and 4000 revs. So at 4000 revs you should have 38 degrees of advance.

Tim
 
I'll dig out my timing light and re-check the timing.
Incidentally, I've re-read the Haynes manual and the timing for the GF engine (as fitted to my 900T) is as follows:

Static: 5 to 7 (degrees) BTDC
Centrifugal advance: 28 +/- 2 (degrees) maximum.

One thought that I've just had is that the garage would have set the timing up manually i.e. by adjusting the dizzy. I've fitted the 123 Electronic ignition conversion which is able to set the advance curve. I haven't played with this yet but need to check if there is some default mapping already set which ends up being compounded with the manual adjustment. Probably not noticeable at tick over but gets worse at the higher revs.

I'll check the readout via the App (connects via bluetooth to my phone) to see if there is anything obvious - although it may already be thinking that it's set at zero baseline. The engine runs and pulls pretty well so I don't think there is anything too far out.

Thinking ahead, it might be a good idea to set the manually adjusted timing back to zero and then set the timing via the 123 App. There are some useful videos on their website that explains how: https://123ignition.com/support/

The video on setting advance curves shows a curve graph, not sure if one of these is available for the 900T - anyone?

In absence of the graph would I set the advance at 6,000 rpm to 28 degrees? Or at 4,800rpm which is where maximum horsepower is supposed to be achieved? I could increase the rev limiter if needed but I'm generally happy to keep it at 6,000rpm due to the age of everything.
 
Yes I would be happy with 800 to 900 revs. In fairness not many 850t/900t have rev counters so as long as the charge light is out and its smooth enough then as long as it's not wobbling around I would be happy.
 
I was having issues with overheating on an 850 sedan and what made a huge difference was using compressed air and blowing out the rad. I was getting minimal airflow through it and when I removed it I discovered it was caked solid from years of oily grime that had been blown into it. While I was in there I also blew out all the bypass hoses and anything else that may have been restricted. I also left the radiator sitting filled with a water/vinegar mix over night and then flushed it, the gunk that came out was sickening!
I also removed the thermostat completely to allow constant water flow. Some disagree with this but cooling was a weakness in these and tbh it on a warm day will climb to 1/4 on the needle. 2000 miles since March and it's still going strong.
 
Gary, one other thing to suggest, you mention an electric fan behind the louvres blowing air in, might you be better turning it so it blows air out thus expelling warm air out? How much air it will draw in as you are motoring along maybe limited, at least air can be sucked/blown out.
If the cooling measures I took in the above didn't work out, I was going to mount an electric van on the lower panel (after cutting it of course!) facing the ground underneath the waterpump to expell warm air out below. The sedan version hasn't got too many options for fans and that was one idea I'd had. If you are running a dynamo instead of an alternator you may need to look at the power draw as I don't think dynamos deliver the same amount of power.
 
Been having a play with the timing today - not my strong point, ended up running as rough as a bag of spanners :cry:

Fortunately, I had the sense to mark the dizzy position first so it was easy to set it back to what the garage set up - now running okay again.

Today is a lot cooler today (by a good 10C) than when I first discovered the overheating problem. The combination of fans (the one sucking air in through the louvres works really well) along with keeping under 40 mph keeps the heater gauge steady at 3/4 (the 123-ignition app reads 90C).

I've already flushed everything through both individually (when everything dismantled) and twice again when everything connected. So I'm pretty confident the waterways are clear.

As keeping under 40 mph seems to keep the temperature manageable I'm wondering whether the thermostat could be the guilty part i.e. not fully opening.

As a quick test to find out I'm going to remove it and try running without one fitted (as suggested in the previous comments by FR85). Like many others, I'm not a great fan of running without the thermostat fitted (as this also acts as a restrictor to slow the flow) but if this solves the hot running it's easy enough to get hold of a new thermostat.

Now to find where I've put my spare gaskets :bang:
 
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