Fiat X19 cooling system diagnostic with GC

[johnv]

The problem : cooling on my GC engine X1/9


It was hard to get this install right .. that is keep the temperature down to the
recommended 75 degrees with this engine, but I thought I had it cracked:

New high capacity alloy radiator
New waterpump
GC modified thermostat
Paraflu
Oil Cooler + thermostat
ThinkAutomotiveradiator fan + override switch
Modified engine lid and air intake ducts
Racetech capillary water and oil temp and oil pressure gauges

Generally speaking, the car runs at 75 degrees, rising to 80 on a hot day in traffic, but back down to 75
on the open road. Recently I have done a couple of longer motorway trips, and I noticed at first that
the temperature would start to creep up, then settle back down to 75.
The last trip this became a lot more pronounced .. the temp would sit at about 72 (at 4500 to 5500 rpm, do the maths!)
then it would rise quite alarmingly to above 80, I would ease off, and it would shoot back down to below 75 .. off I go again.

Call to GC ... could be the gauge, unlikely, could be the thermostat, unlikely .. Guy then hit on the answer. One
of the heater hoses was collapsing, probably one of the longer ones that carry the coolant to and from the pipes
that run under the car. These are probably one of the very few bits of the car that I have never replaced. The solution
will be to try to replace with aluminium if possible, or at least new, stronger ones .. suggestions gratefully received!


I think the large hose is the culprit, but there's not much room left in there!

[James Bowen]

John,

I don't want to turn this post into a guessing game of possible causes but...., I had problems of a similar nature with mine, but when running at track days. I never managed to put my finger on the exact cause but the below mentioned, or a combination of, worked.

1.) The water level in the expantion tank needs to be fairly high. At 3/4, or slightly more. I was running it at 1/2, and I suspect that the level was lower than the highest point in the system, and a possible cause of air locks, which travelled to the radiator.

2.) Making sure the rad. was bled when the engine was hot, and rad fan was kicking in. The switch to cut the fan in is around 90degC

3.) This probably won't apply to your car but, I had gotten rid of the heater matrix, and simply plumbed the heater inlet and outlets from the cylinder head together. I belive that this was causing a bypass of the water pump feed pipe, and caused the water to be circulated around the cylinder head, not allowing it to the thermostat, and hence rest of the engine.

On another note, your hoses look pretty good compared to mine, which are shot, especially at the bottom bend where they join the metal pipes running to the front of the car. The engine doesn't drop below 5,000 rpm on the track, and haven't, I believe experienced that problem. I'm not by any means disagreeing with Guy, and only offer my experiences to hopefully, assist.

Regards, James