Cooling modification

[Mxgrds]

My X Uno turbo’s coolwater gets pretty hot when driving 120km/h on the highway for some time. I posted that in a group on facebook and someone suggested to block the thermostat outlet to the tank in order to force that flow to go also to the rad for better cooling. I looked carefull to the thermostat and found that the in- and outlet are almost in the same chamber of the thermostat. So the overpressure will found it’s way through the inlet at the bottom of the tank. In my case the turbo cooling is now using the inlet on the top of the tank.
What do tou think? Usefull? Or does it just mean that the faster rad flow, cools down less?

 

[ng_randolph]

I don't think this would have any meaningful effect on cooling. What circulates through the reservoir is a very small fraction of what goes through the radiator. What is the condition of your radiator?

 

[Mxgrds]

I don't think this would have any meaningful effect on cooling. What circulates through the reservoir is a very small fraction of what goes through the radiator. What is the condition of your radiator?

It’s a new aluminium scirocco rad.
I now it is not a small fraction. I have watched it pooring in into the tank. That is a strong flow that stirres up the coolwater in the tank severely.

 

[Dr.Jeff]

Can you illustrate how blocking off the T-stat outlet would work? It doesn't sound right to me.

Naturally prolonged RPM running ("driving 120km/h on the highway for some time") with a turbo will generate MASSIVE amounts of heat from the turbo unit. I'd look at the turbo's cooling first. Not 100% sure I understand how you have the cooling circuit for the turbo configured ("the turbo cooling is now using the inlet on the top of the tank")? Also it may require a oil cooler (if you don't already have one, sorry I can't recall) to keep the hot oil from the turbo from heating up the engine and therefore cooling system.

And I'd consider managing the heat radiating off the turbo itself, away from all other components, to reduce the effect it has on raising their temps - which will increase the engine/cooling system temp.

In my opinion the VW radiator has a lot more cooling capacity (heat exchange) than any X1/9 radiator - stock or aluminum. And that seems to be supported by the fact the temp is good when in stop and go driving. So I doubt the rad is the problem. I'm sure all of the remaining cooling system is functioning properly?

 

[Bjorn Nilson]

I had the same problem on my UT engine, or even still have. I haven't gotten an opportunity to test the new alu rad in hot weather yet. If the new radiator doesn't solve the heating problem I am thinking of mounting the X1/9 thermostat housing that is different from UT. However, the x1/9 housing does not have the temp sensor that is necessary for ECU.
Return line from turbo must be connected to expansion tank to work properly and I don't think it is causing the overheating.

 

[Mxgrds]

First, driving 120 km/h doesn’t use the turbo at all. Turbo pressure is -0,4 bar. The turbo is only under stress at hard acceleration or driving over 160 km/h.
I have not installed an oil cooler on this X yet. Allthough I doubt if that makes a big difference. It has been pretty cold last month.

The route through the tank allows hot coolwater coming out of the engine to bypass the thermostat when open, to flow directly into the motor again without being cooled down by the rad. Cutting off this route forces more coolant into the radiator.

In the picture is the red line the flow through the tank. You can see the outlet of the tank goes to flow to the waterpump, bypassing the radiator. Blocking the red flow forces all coolant coming from the engine to flow to the radiator.

 

[Dr.Jeff]

Return line from turbo must be connected to expansion tank to work properly and I don't think it is causing the overheating.

Agreed, but he said "In my case the turbo cooling is now using the inlet on the top of the tank." I think that means the SUPPLY line to the turbo?

 

[Dr.Jeff]

First, driving 120 km/h doesn’t use the turbo at all. Turbo pressure is -0,4 bar. The turbo is only under stress at hard acceleration or driving over 160 km/h.
I have not installed an oil cooler on this X yet. Allthough I doubt if that makes a big difference. It has been pretty cold last month.

The route through the tank allows hot coolwater coming out of the engine to bypass the thermostat when open, to flow directly into the motor again without being cooled down by the rad. Cutting off this route forces more coolant into the radiator.

In the picture is the red line the flow through the tank. You can see the outlet of the tank goes to flow to the waterpump, bypassing the radiator. Blocking the red flow forces all coolant coming from the engine to flow to the radiator.

I disagree about the turbo not generating lots of heat when running at constant high speeds. But this only my opinion.
I see more what you mean by thermostat housing flow, but I don't see that as an issue...the thermostat only bypasses when the engine is not hot. I'm still not clear how your turbo cooling plumbing is routed?

 

[Mxgrds]

I had the same problem on my UT engine, or even still have. I haven't gotten an opportunity to test the new alu rad in hot weather yet. If the new radiator doesn't solve the heating problem I am thinking of mounting the X1/9 thermostat housing that is different from UT. However, the x1/9 housing does not have the temp sensor that is necessary for ECU.
Return line from turbo must be connected to expansion tank to work properly and I don't think it is causing the overheating.

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?

 

[Mxgrds]

Supply turbo: directly from block just behind turbo
Outlet turbo: to top inlet tank

 

[Mxgrds]

I disagree about the turbo not generating lots of heat when running at constant high speeds. But this only my opinion.
I see more what you mean by thermostat housing flow, but I don't see that as an issue...the thermostat only bypasses when the engine is not hot. I'm still not clear how your turbo cooling plumbing is routed?

At -0,4 bar the turbo does not generate extra heat. It is hot offcourse, because it is attached to the exhaust. The turbo itself start to generate heat when air is compressed, that is > 0 bar turbo pressure.

 

[Dr.Jeff]

Supply turbo: directly from block just behind turbo
Outlet turbo: to top inlet tank

Thanks, I misunderstood a earlier comment. That sounds like what I'd expect to work well.

I agree with your comment on the function of the expansion tank. So the only "flow through the tank" would mainly be the eb and flow of coolant as it expands and contracts. Therefore I don't see it as an issue here.

 

[Dr.Jeff]

At -0,4 bar the turbo does not generate extra heat. It is hot offcourse, because it is attached to the exhaust. The turbo itself start to generate heat when air is compressed, that is > 0 bar turbo pressure.

I missed the "-" sign. I'm surprised the system is efficient enough to not have any actual boost at that RPM. I'd expect it to be pumping out more energy just to keep the vehicle moving through the air resistance at those speeds. But I agree with the point that constant cruising can be a low load condition, and therefore less boost.

 

[Mxgrds]

I had the same problem on my UT engine, or even still have. I haven't gotten an opportunity to test the new alu rad in hot weather yet. If the new radiator doesn't solve the heating problem I am thinking of mounting the X1/9 thermostat housing that is different from UT. However, the x1/9 housing does not have the temp sensor that is necessary for ECU.
Return line from turbo must be connected to expansion tank to work properly and I don't think it is causing the overheating.

I have another X with an Uno turbo with standard X radiator and injection type thermostat housing. No problems with the cooling. Driven through Germany over the highway 130/140 km/h at 30 degrees celsius for hours. Heavy packed with tent on the back. Oil temp at 120 degrees celsius. Oil cooler installed, though.

 

[Mxgrds]

Thanks, I misunderstood a earlier comment. That sounds like what I'd expect to work well.

I agree with your comment on the function of the expansion tank. So the only "flow through the tank" would mainly be the eb and flow of coolant as it expands and contracts. Therefore I don't see it as an issue here.

Just rev your engine and look into the tank. There is a hard flow of coolant coming from the inlet. At high rpm it is so strong it makes air bubbles which can be sucked in at the bottom.

 

[Dr.Jeff]

Getting back to the question about blocking off the t-stat housing bypass. Remember that the T-stat is a dual diaphragm design; as one pathway is opened the other one is closed. So it only "bypasses" under certain conditions (i.e. when cold), and even then it is only a partial bypass as those diaphragms cycle partially back and forth. So there isn't much in the way of "short cycling" - hot and cold coolant intermixing - and virtually none when the engine is fully warmed up (or hot).

This should also reduce the flow into the overflow tank as the engine fully warms up. Unfortunately you cannot observe that when the engine is hot. But it should not be a hard flow like you see when it isn't warmed up (i.e. cold). So I still don't see this as a cause for your hot coolant temps.

 

[Mxgrds]

I missed the "-" sign. I'm surprised the system is efficient enough to not have any actual boost at that RPM. I'd expect it to be pumping out more energy just to keep the vehicle moving through the air resistance at those speeds. But I agree with the point that constant cruising can be a low load condition, and therefore less boost.

I was suprised too. My impression is that the 1300 turbo engine is stronger than the 1500 injection, even if the turbo boost is not used. Mine was a 1500 injection before converted.

 

[Dr.Jeff]

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?

 

[Mxgrds]

Getting back to the question about blocking off the t-stat housing bypass. Remember that the T-stat is a dual diaphragm design; as one pathway is opened the other one is closed. So it only "bypasses" under certain conditions (i.e. when cold), and even then it is only a partial bypass as those diaphragms cycle partially back and forth. So there isn't much in the way of "short cycling" - hot and cold coolant intermixing - and virtually none when the engine is fully warmed up (or hot).

This should also reduce the flow into the overflow tank as the engine fully warms up. Unfortunately you cannot observe that when the engine is hot. But it should not be a hard flow like you see when it isn't warmed up (i.e. cold). So I still don't see this as a cause for your hot coolant temps.

Yes it is possible to observe the flow when hot. Carefully remove the cap when hot.

The coolant flow will flow the route of the least resistance. Which is the short route through the tank and not the 6 meter route through the radiator. Lucky the diameter to the tank restricts most of the flow that direction. Pinching off that flow entirely forces all hot coolant to the radiator.

 

[Dr.Jeff]

Yes it is possible to observe the flow when hot. Carefully remove the cap when hot.

The coolant flow will flow the route of the least resistance. Which is the short route through the tank and not the 6 meter route through the radiator. Lucky the diameter to the tank restricts most of the flow that direction. Pinching off that flow entirely forces all hot coolant to the radiator.

So why don't all X's have this same hot cruising problem?