Radiator overflow

[Nigel1967]

Hello all,
I have a series one Fulvia zagato which has a very minor weep in the top of the radiator so I added some Wynns rad seal to see if that works. In doing so, the coolant level in the radiator is higher than it normally is and so when it warms up is blowing some out of the overflow and the temperature gauge goes further over until the thermostat opens.
The question I can’t fathom is, would having too much coolant has these effects ?
Thanks for any thoughts
Best
Nigel

[lancialulu]

Without  knowing your specific situation I can  tell you that Fulvias "self level" when hot. Normally to around 1/2" above the core. People with Fulvias often make the mistake that the level should be higher and keep topping  up suspecting a head gasket or hose leak.... Maybe,  but generally the rad does not like being full.

Do you know if your thermostat has a c2mm hole that acts as a bleed before opening. Some thermostats are without this hole which should be vertically uppermost.

[Nigel1967]

Ah I see. That makes sense .
I’ve never had a problem before filling with extra coolant so I’ll see what happens next time out.
I actually don’t know what type of stat I have but I’ll see if I can take a look.
Not sure why the gauge goes further toward the hot than previous but once the level has sorted itself out maybe it’ll revert.
Thanks very much indeed
Best
Nigel

[Richard Fridd]

Am I correct in thinking that the space in the top of the radiator half an inch above the core is the tank for expansion?

  Richard

[Nigel1967]

Hi Richard ,
I think you’re right .in overfilling my rad I’ve removed the expansion buffer hence the water coming out of the overflow.
Still can’t understand why the stat seems to take longer to open.
That said , even with the gauge virtually at 100, the rad cap is fairly cool to the touch.
All very confusing
Best
Nigel

[Richard Fridd]

I would try another thermostat at this point. And use a suitable thermometer.

  Richard

[Spider2]

Would the rad seal have clogged up the stat? My 1.3 Zagato runs a needle's width to the right of 70 degrees. Rock steady.

[Nigel1967]

that did cross my mind but apparently it doesn't.
Mine always moves past the half way point until the stat opens then comes back.
It then repeats this process all the time the engine is running.
Maybe i have the wrong stat but it's never overheated even in hot Le Mans traffic queues.

[lancialulu]

Do you have a mismatch of coolant temp sender unit (do you have Jaeger instruments instead of Veglia?). Does your thermostat have a 2 mm bleed hole (should be at 12 oclock when  thermostat is crewed in)?

[Nigel1967]

i have Veglia instruments but i'm not with the car at the moment to look at the stat.
Can you see a bleed hole while its in situ?

[fay66]

i have Veglia instruments but i'm not with the car at the moment to look at the stat.
Can you see a bleed hole while its in situ?

Yes once the top hose is pulled off at housing.
Before I realised that there was no bleed hole I'd had no end of problems with overheating, and the temperature gauge reading very high, I came to the conclusion rightly or wrongly, that the sender sat in what had become a hot spot .
I had a spare new thermostat that i fitted to see if that cured the problem, not realising that also had no bleed hole.
A bit later, I accidentally left the rad cap off, and everything was as it should be so I took the thermostat out and suddenly realised that there was no bleed hole
As I was just about to go on the Fulvia Knights Rallye to Turin in 2013 for Fulvia 50 Anniversary , i decided to drill a 1/16" hole after determining the position for drilling by installing the thermostat to make sure the hole would be at the top.
I then refilled with fresh coolant.
End of story, I've never had the problem since .and my 2000 mile trip to Turin and back via Belgium was perfect, apart from a bonnet release cable breaking  on the way home.
Brian
8227

[Nigel1967]

Hi Brian,

Thanks very much. I've never had an overheating issue until the rad seal was added. I'll drain some out tomorrow back to the level its always been and re-asses.
My gauge is always floating between bang in the middle and about 2/3rd across the dial as the stat is opening and closing i guess.
2000 miles to Turin sounds a good trip.
Thanks again
Best
nigel.

[Richard Fridd]

Can the sealant block the bleed hole?

  Richard

[Spider2]

I think Richard has pinpointed the problem. Take the hose off the front of the housing and the stat is staring at you. My money is that the bleed hole is blocked.

[lancianut666]

Love it! remote fault sensing. I was thinking head gasket mischief.
Clarkey