Cooling modification

Dr.Jeff said:
I'd suspect some other area of the cooling system to be the reason for hotter temps while cruising. Perhaps something like that RPM happens to be a speed for the water pump impeller to cause cavitation, or such?
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That might the case. I already ordered a new waterpump as the current waterpump might be for the 1500 injection and not for the turbo. Allthough I am not sure if there is a difference. Might be that the turbo has a smaller pulley and therefore a higher capacity.
 
If the radiator or fans were the problem then it would be the opposite, hot when sitting still and cool when cruising. If the coolant pipes (or other areas of the circuit) were partially blocked then I'd expect it to run hotter under most any condition (certainly more than just cruising). As I said (somewhat jokingly) if it was the design of the bypass T-stat then I'd expect more (all?) of these cars to have the same problem. So what does that leave?

Maybe there is something to the water pump idea? How old is it? Which type of impeller does it have? What's the gap on it? Are the pulleys (crank and pump) the same as other UT's? Just asking all questions that come to my mind.
 
A little off topic, but what engine RPM does it cruise at when 120km/h? That's a pretty decent speed, so depending on the gearing (most X's are rather low geared), the engine is likely spinning fairly fast?

I like to "brainstorm" like this. But gotta go, so will look back later.
 
Dr.Jeff said:
A little off topic, but what engine RPM does it cruise at when 120km/h? That's a pretty decent speed, so depending on the gearing (most X's are rather low geared), the engine is likely spinning fairly fast?

I like to "brainstorm" like this. But gotta go, so will look back later.
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5 speed 1500 standard gearbox. So 4000 rpm for 120km/h. To compare the UT gearbox is 3500 rpm at that speed.
 
Dr.Jeff said:
How would that affect the turbo cooling circuit? Not saying it would, just a thought.
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Not the turbo cooling circuit, but the whole circuit. I am not sure if it brings extra cooling, but it might.
Dr.Jeff said:
Another thought. Maybe the T-stat itself isn't opening all the way? What condition is it in?
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Good question. Together with the waterpump also a new thermostat arrives. I will know when replaced.
 
Mxgrds said:
Not the turbo cooling circuit, but the whole circuit.
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Understood, but I was asking could this also have some sort of unwanted effect on the turbo's cooling circuit? Just by virtue it involves the overflow tank, plumbing/flow to it, and therefore maybe the turbo cooling pathway.


Mxgrds said:
So 4000 rpm for 120km/h. To compare the UT gearbox is 3500 rpm at that speed.
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That shouldn't be significant.
 
Mxgrds said:
The return line from the turbo in now my only return connection to the tank. In my understanding the expansion tank is there to deal with the expansion of the coolant and keeping a certain extra available. Why should there be a flow through the tank?
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Having flow through the reservoir helps purging any air that might otherwise be accumulating in the system. Most cars don't use a pressurized reservoir like the X1/9, but an overflow tank open to atmosphere, and in this case there is no flow through the tank. As the radiator cap opens at its pressure limit, coolant/air is let into the tank, and when engine cools off, under-pressure in the cooling system draws coolant back from the tank.
 
Mxgrds said:
That might the case. I already ordered a new waterpump as the current waterpump might be for the 1500 injection and not for the turbo. Allthough I am not sure if there is a difference. Might be that the turbo has a smaller pulley and therefore a higher capacity.
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When you get the new pump, be sure to check impeller to housing clearance. Factory spec is 0.8 - 1.3mm, adjusted by moving the impeller on the shaft.
 
ng_randolph said:
Having flow through the reservoir helps purging any air that might otherwise be accumulating in the system. Most cars don't use a pressurized reservoir like the X1/9, but an overflow tank open to atmosphere, and in this case there is no flow through the tank. As the radiator cap opens at its pressure limit, coolant/air is let into the tank, and when engine cools off, under-pressure in the cooling system draws coolant back from the tank.
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purging from or introducing air into the system?
Post in thread 'Sucking air???'
https://xwebforums.com/forum/index.php?threads/sucking-air.24950/post-238161
 
Not to be argumentative, but I've always questioned the notion that air bubbles going into the overflow tank creates air in the system. Afterall where did those bubbles come from in the first place, it is a closed system? So the air may be moving around, and seen as tiny bubbles in the tank, but it was already there. In other words, the coolant going into the tank did not create a new source of air added to the system. If anything, the air going into the tank may allow it an opportunity to collect there and be more easily bled by venting the cap.
 
The only place in the system trapped air is a problem is in the rad. Therefor I installed an automatic bleeder on the rad. No problems since.
 
Dr.Jeff said:
Not to be argumentative, but I've always questioned the notion that air bubbles going into the overflow tank creates air in the system. Afterall where did those bubbles come from in the first place, it is a closed system? So the air may be moving around, and seen as tiny bubbles in the tank, but it was already there. In other words, the coolant going into the tank did not create a new source of air added to the system. If anything, the air going into the tank may allow it an opportunity to collect there and be more easily bled by venting the cap.
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These airbubbles are created IN the tank because the strong flow from the inlet stirres up the coolant so that it mixes with the air above the coolant. Especially when under pressure the air is easily solved in the coolant. Take a glass of clear water and stirre it up heavily. You will see airbubbles on the bottom of the glass While the water is in motion. The coolant system is not a vacuum system without air!
 
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Dr.Jeff said:
Please remind me what this is, as I'm sure we've discussed it but I don't recall.
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I extended the bleed screw opening with a hose to the left frontlight cavity. There I installed an automatic bleeder from central heating systems. It is a flooter principle. Air that arrives in the rad will go to the highest point. That is the bleed screw opening, through the hose to the flooter. The flooter will fall dry, opening, let the air escape untill it floats again on the coolant. Very efficient. Don’t need to worry when driving high speeds for a long time.
 
I think your plumbing approach is the problem.

You chose an easy way to plumb this rather than ensuring the turbo coolant goes directly to the radiator. I would recommend buying or making a transition for the coolant leaving the turbo to go around the engine to join the coolant going directly to the radiator. This could be placed inline into the rubber hose leading from the engine to the main hard cooling line.

This would ensure coolant coming from the turbo always bypasses the thermostat entirely and the resultant heat is properly dealt with in the radiator rather than mixing into the cooled water bringing the overall temperature up.

The thermostat never completely closes off the flow from the return line so there will always be flow through the turbo.

You could also consider a small coolant pump like many other turbo cars to pull coolant out of the cooled return flow to the turbo and back into the radiator hot side as an entirely separate system which shares the same supply.
 
Mxgrds said:
so that it mixes with the air above the coolant
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That's my point, the air was already in there. The molecules of air and water will mix just from the circulation. Agitation speeds it up, but there are a finite number of those molecules in the contained space and it cannot create more than already exists. In other words, it may distribute the existing air more but it won't make more of it. So eventually that air will come back to the tank - as the hot/cold cycles and circulation happen. That's why the air space in the tank doesn't keep getting larger (unless you have a leak).
 
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