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Old 13-10-2014   #1
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900t overheating issues again

unfortunatly our lill 900t is having over heating issues again, after a run of 20 or 30 miles we pull up and even though the gauge is only reading A on the WATER temp gauge the rad is bubbling and clonking, just done a full engine rebuild head gasket rings, seals the lot , head was checked and wasnt warped , reground the valves , did the stem seals big end and crank bearings, rad has been re cored
checked the water and no hydrocarbon reading with tester so no cylinder or head leak, new rad cap and thermostat, all the tin work is in place including making a new shield around the 4 branch manifold exhaust, all the airways are clear as well, when shes reved when at standstill she blows a hurricane of hot air out the bottom ducting as she should do

and still we get this issue

im now suspecting the the water pump, is there a conversion kit to replace the antiquated pump as i want to put an electric cooling fan in also to remove the one from the water pump

any other clues would be greatly appreciated

cheers

tim
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Old 15-10-2014   #2
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Re: 900t overheating issues again

double check for air-locks too,

no idea on pumps,
maybe look in the 126 section for pointers..,

charlie
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Old 29-12-2014   #3
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Re: 900t overheating issues again

Mine did this when I got it many years ago. What solved it in the end was fitting an under tray to the engine compartment, there were bracket's on mine which suggested such an item was fitted from factory. What the under tray did was ensure that COOL air was brought through the radiator from underneath (form memory had sort of a scoop it pulled air in from). Then the warm air was exhaled in to the engine compartment and on out through the vents. Did that and it went from being a chronic overheater to never overheating again... despite being run over BIG mountain passes etc. Hope that helps.
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Old 02-02-2015   #4
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Re: 900t overheating issues again

My 900T had a factory tray behind the radiator. It is important to stop the hot air recycling through the radiator. I regularly used mine going skiing and never had an overheating issue despite having put all the 850 sport bits on it.

Not sure about the electric fan idea. This van does not have ram effect of air when driving so fan likely to run continuously. Fan may have short life.
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Last edited by Maigretnz; 02-02-2015 at 21:12.
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Old 08-02-2015   #5
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Re: 900t overheating issues again

Is the timing definitely spot on? That can contribute if its not quite right. I tried setting mine with an ammeter (dwell angle) a while back but resorted to the good old main pulley/strobe technique in the end (once I'd painted the timing marks white so that I could see them).
The cooling on those engines seems to be only just sufficient so everything needs to be in good order, could be a combination of things. Have you flushed out all the waterways (including heater circuit), flush it in both directions if you do have a go.
Water pumps are easy enough to come by, just make sure you get a 4 bolt not 3 bolt type.
Hope you get it sorted,
Andy
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Last edited by chick850t; 08-02-2015 at 11:31.
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Old 08-02-2015   #6
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Re: 900t overheating issues again

Where are you getting the 4 bolt pumps from Andy as I seem to be struggling to get one for mine. Thanks
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Old 08-02-2015   #7
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Re: 900t overheating issues again

Quote Originally Posted by chick850t View Post
Is the timing definitely spot on? That can contribute if its not quite right. I tried setting mine with an ammeter (dwell angle) a while back but resorted to the good old main pulley/strobe technique in the end (once I'd painted the timing marks white so that I could see them).
The cooling on those engines seems to be only just sufficient so everything needs to be in good order, could be a combination of things. Have you flushed out all the waterways (including heater circuit), flush it in both directions if you do have a go.
Water pumps are easy enough to come by, just make sure you get a 4 bolt not 3 bolt type.
Hope you get it sorted,
Andy
The dwell angle which relates to points gap and the ignition timing via the strobe are two completely different things. Both important.

I worked my van hard on mountain roads and never had an issue with overheating. The tray under the motor missing is usually the culprit when people have problems.
phate316 hasn't got back as to whether this is the case.
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Old 08-02-2015   #8
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Re: 900t overheating issues again

Dwell adjustment http://www.howacarworks.com/ignition...he-dwell-angle

Timing with strobe http://www.howacarworks.com/ignition...oscopic-timing

A trap with this engine which caught me out once. The pulley on the end of the crankshaft only locates by a small amount with the key on the shaft. This can strip off and this causes the pulley to rotate a few degrees. This will not affect the operation of the engine so if working ok will continue to do so. However the timing marks will now be out of alignment. So if in doubt remove the pulley and check the location with the key. I repaired mine with a new key and brazing/filing the damage to the pulley
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Last edited by Maigretnz; 09-02-2015 at 00:33. Reason: quirks
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Old 09-02-2015   #9
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Re: 900t overheating issues again

Ref. the 4 bolt water pumps, just had a quick look on eBay and there's one on there at the moment:

http://www.ebay.co.uk/itm/Fiat-850-C...item487209dd5b

Ricambio also sell them:

http://www.ricambio.co.uk/69-fiat/54...fiat-850--900-

Hope that helps.

Cheers,

Andy
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Old 09-05-2015   #10
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Re: 900t overheating issues again

cheers for extra replys to overheating issues, timing was set and checked when rebuild was done and just strobed it again and is still bang on as per fiat workshop manual , also many thanks for info on pumps but im looking to get away completely from the mechanical aspect of water pump and cooling fan completely and im currenty exploring the concept having an engineering firm build me a hose connector to fit in place of the pump mounting and put an electronic pump and thermal switch fan to replace both as in modern engines, im also in the middle of testing the head to make sure its not warped
eg block test for co2, pressure loss test and compression test

will hopefully figure her out as shes looking very forlorn sitting in the workshop and not on the road

caio for now
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Old 13-05-2015   #11
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Re: 900t overheating issues again

Can you confirm the tray is in place behind the radiator?
The existing set-up has to be very worn not to work and actually works well. I did a lot of mountain work with mine and never had an issue.
Did you remove and check the crank pulley to see if the key is stripped? This will put the timing mark out of alignment.
The air is pushed forward in this vehicle so there is no ram effect when driving as with most cars. This means an electric fan would have to run continuously which nullifies the purpose of putting it on. The best option to upgrade cooling system would be a new radiator core and get the fattest one fitted that the rad shop can do. There is no point in pumping more air and water through your existing radiator if that is the limiting factor.
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Last edited by Maigretnz; 13-05-2015 at 01:34.
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Old 09-08-2020   #12
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Re: 900t overheating issues again

My 900t (Connie) overheats after just a few miles

I've checked through the advice on overheating, flushed rad/engine, checked thermostat, timing & carburettor, under trays in place (albeit ones I've had to make myself) and Connie is still hitting the red zone after just 5 miles.

I fitted a 4-branch exhaust so the new under tray doesn't cover as much area as the original, so I expect there will be more heat coming into the engine bay. However, I've lagged the 4-branch manifold to keep the heat down as much as possible.

Under the radiator side under tray I've added ducting to take the heat beyond the bumper - to help stop heat recirculating into the engine bay. (There are no rubber strips on the new under trays to make a flush seal to the engine.)

I had hoped to switch to using an electric rad fan but as there is no air-ram effect this was running continuously and didn't keep the heat under control in any case. I've put the engine driven fan and cowlings back, leaving the electric fan in place as a booster - Connie used to get very hot stuck in traffic.

The electric fan kicks in at 95C but even with the engine driven fan and electric fan running together they can't keep the heat under control. The airflow is working well and the additional ducting works well - you wouldn't want to stand in front of the outlet too long otherwise you would burn your legs.

The only way to keep the heater under control is to have the cabin heat on full - not great in this weather. Even then the temperature gauge is at 3/4 on a flat road. (As turning the cabin heater on helps I think the water pump is working okay, there is no noise from it either.)

I did change the alternator not long before Connie came of the road (14 years ago). At the time I couldn't get hold of a replacement so ended up modifying a different one (higher output at 65 amps). However, the spindle size was different necessitating a different pulley. The new pulley is smaller that the original with both sizes the same.

The alternator pulley diameter sizes are as follows:

Original pulley outer 8.5cm (drive belt from engine).
Original pulley inner 9.7cm (alternator to water pump).

The new pulley is 7cm inner and outer.

My thinking is that as the new pulley is smaller it will be spinning faster (driven from the engine). Therefore the loss of gearing to the water pump will be off-set by the faster spin. There is probably a way to work this out mathematically but I'm thinking that the water pump will be spinning roughly the same - or at least not enough difference to contribute to the over heating problem to this extent.

In one of the threads on overheating there was a comment about checking for airlocks. However, apart from pulling the pipes off to see if the water flows out there doesn't appear to be any bleed valves anywhere.

If you did this, which pipes would you pull off? and wouldn't this risk putting air back into the system if you did it.

Any other suggestions to cure the overheating would be appreciated.
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Old 09-08-2020   #13
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Re: 900t overheating issues again

A general viewpoint:

If the circulation to the heater matrix is good.. then its circulating fine.. with limited air pockets

Apart from admiring from afar..

I dont know much about your system


Have you got a bleed point on top of Rad?

Another trick is elevate the edge of vehicle.. so the rad filler point is tallest

Run up to temp with filler cap off..

It will 'burp' it self easily.. the level should drop as the fan cuts in
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Old 09-08-2020   #14
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Re: 900t overheating issues again

Thanks for the reply.

There are no bleed points anywhere (at least none that I can find), only the radiator cap. I haven't tried running Connie up to temperature without the rad cap on so will give that a try - the rad cap is the highest point of the cooling system.

Since my post this morning I've been trying out a few things, as follows.

Ran on idle to time how long it takes to get up to operating temperature (middle of the temperature gauge) - this took around 12 minutes. The readout from the 123-Ignition app showed the temperature as 60C at this point.

While still idling the temperature continued to climb until the gauge read just below the red line. This was 80C on the 123 App and 90C on the electric fan - cut in point for the fan. The temperature dropped 10C (fan cut off) and then yo-yo'd within this range while still idling.

I then removed the engine cover and took Connie out for a short run (5/6 miles). The temperature gauge settled around 3/4 to 4/5th with the electric fan cutting in and out - the 123 App registered 75C to 85C. This is about the same result as running with the cabin heater on full (without getting heat stroke) but obviously not a practical long term solution.

I'll try the 'burp method' later (once Connie has cooled down). If no joy I'll give it another rad flush on the off-chance that some gunk has released since I gave everything a flush through.
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Old 09-08-2020   #15
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Re: 900t overheating issues again

A few bubbles but no burp
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