JohnC wrote:gchristofi wrote:Well, it does open eventually. A boiling kettle won't do it and the pan on the stove is seriously bubbling before it moves. Considering 88c rating doers this sound off? Are they supposed to start opening at 88 or be fully open?
Of course it could be your new thermostat, but I would not give up on it just yet. Bubbling water does not indicate Boiling Water. Water will bubble long before it reaches boiling point (100 degrees C), In fact the chances of ever attaining boiling point in a kettle or pan is extremely unlikely.
The only true way of checking a thermostat is in a pan but with a thermometer reading the temperature of the water.
The fact that this stat does open in a pan of bubbling water is a very good sign that it is OK.
My take on this problems with overheating, as Lee touched upon, is that you hit the same problem that many GTA owners have had which is well documented on this forum of ineffective bleeding ….. consequently, there is a large volume of air trapped in the heads having refilled the cooling system. Add to that your stated 100 mile test run with less coolant in the system than there should be. Now when this happens the stat fitted at the highest point of the engine, does not get affected by the coolant as there is a large pocket of air trapped underneath it, until such time as the water vapour produced by the boiling coolant lower down reaches the stat which then, hopefully, opens. Now the stat is open, but there is not enough coolant in the system to maintain a steady engine temperature.
This, in GTA's, is mainly caused by the thermostat not having a jiggle valve … (610's do have them) … and that is why I have suggested a small hole is drilled in the stat to allow the trapped air beneath the stat to bleed through, but slowly. This, of course, is not he only reason these Alp's are difficult to bleed. There are other Golden rules like jacking the rear of the car up so the long coolant in the pipes under the car allow the coolant to push the air up the pipes towards the engine. The next is to fill the reservoir slowly to allow the air to bleed through the small hole in the stat to release the air trapped in the heads …. I decant the coolant into a 1 litre bottle for filling, and let it settle as I decant the next bottle. If you try and pour it in from, say, a 5 litre container you will stop the displaced air from coming back up into the reservoir bottle via the same small hose you are filling through attached to the bottom of the reservoir, which is its only way out other than the small stat hole. The bleed valve in the top of the stat housing is as useful as a chocolate teapot as it is above the closed stat and anyway, if you look at the hose fitted to the top of the stat housing, you will see that any air above the stat (where the bleed nipple is) will travel along the hose and bleed out into the reservoir via the small hose into the top of the reservoir as will the air passing through the small hole in the stat. My final trick when bleeding the rad, is to fill the reservoir up and remove completely the bung on the rad bleeding tube, to allow the coolant to “gush” out which will allow all the air to be picked up and forced down the tube.
In my view, that will get rid of as much air as possible while static. There will be other small pockets of air in the system, and to get rid of them, go for a short run at various engine revs, say, 2 to 3 miles, just sufficient to get a good of flow of coolant around the with the engine up to temperature …. not a long run, just in case …. leave the car to cool then top up. That should be it, but check the coolant level after the next few trips and top up if necessary.
Apologises to all the members who know about this, but it has been a long time since this problem has come up, so this is for our newer members who might have trouble bleeding the cooling system of these GTA's. I hope this might help them.
John
Thanks for the advice on bleeding. I thought I'd been doing it well enough but there's a few pointers that I had missed. I was filling from 5l containers and not jacking the back of the car. I did get clear flow from the rad bleed and the stat bleed, but as you say, with no jiggle valve, this might have not been effective as I thought.
For now, the car is running very happily without the stat, but upon reading your description of operation posted in the members section, I do wonder if I might be missing some important flow around the heads as controlled by the second lower disc on the stat. Was planning on getting a thermocouple / thermometer to test the simon stat I have to make sure It is actually faulty. A worthwhile investment I think to know exactly what was going on and what the solution should be. I did feel the spring of the stat become easier to compress as it cooled so that didn't feel intuitively correct. Also seemed like the water in the bubbling pan was getting as close to it's atmospheric boiling point as possible without the benefit of superheating...... enjoyed the sauna though! Will report back when I get the thermometer but in the meantime, going to enjoy fixing a few cosmetics
So, taped wires out the way for now.... hoping not to need the reversing lights on track.
