Coolant Flow Path '82 300TDT
 

Does anyone know the flow path of the coolant in the engine and most specifically the waterpump connections? I am in the process of retrofitting a VNT turbo that has a water-cooled center cartridge and want to do a hose routing that makes sense. TIA.

Andrew

The water pump forces "cool" water into the block. It returns "hot" via the head. From the head it can go one of two places:

1) Down the bypass hose which is straight out the bottom of the thermostat housing and back to the water pump.

2) Off to the radiator.

The thermostat determines which direction it goes. The thermostat starts off "closed" and all the hot coolant is sent down the bypass to the water pump.

When the thermostat begins to open, it simultaneously begins to close the bypass. Opening the thermostat allows the coolant to return from the radiator. With the bypass beginning to close, the coolant must head off to the top of the radiator.

Once the engine reaches 94C., the bypass is fully closed to the hot coolant exiting the head and the return from the radiator is fully open. All coolant from the head goes to the radiator and none of it goes down the bypass. All the coolant that returns from the radiator will then head down the bypass to the water pump.

So I gather that the pressure side of the pump only goes directly into the block. That kinda stinks. Hmmm, any recommends on plumbing in a water-cooled turbo?

Andrew

Here is the flow path.

Which turbo are you using?

GT2556V from an Opel 3.0L TD.

Thanks for the flow paths. For lack of a simpler path, I guess I will tie into the heater circuit (always flows). I'd prefer the cooler coolant, but I don't think I'll tap a fitting into the block. Anyway, once N.O.T. is reached, the oil should always be hotter than the coolant leaving the engine, so I guess it won't hurt. I don't really care for dumping extra heat back into the water-pump, tho. Hmmm.

Andrew

The heater circuit has a valve that stops flow when the heater is off.

Here is your thread in the VW GTD forum for those that might want to see what you are doing. (Didn't you mean GT2559V? Only BMW used the 2556.)
http://vwdiesel.net/phpBB/viewtopic.php?t=10365

There is a block drain connection on the exhaust side of the block. You might consider taking a line from that point (on a 240D it is just ahead of the starter bracket as I recall) and going back in to the thermostat housing somewhere where on the suction side of the pump, but on the impeller side of the thermostat proper. Jim

Yup, I meant GT2559V. I would take from the heater circuit prior to either valve, and return after both. I like the block idea that was just mentioned, tho. I'll investigate some more.

Andrew

Check out post 21 for my plan for plumbing a Water cooled turbo:

http://schumanautomotive.com/forums/showthread.php?t=4580

I really appreciate the post. Very good info.

Andrew

With regard to this project, I'm nearing completion. I still need to plumb in the water-cooling portion of the turbocharger. The two basic suggestions have been to take coolant from either the heater circuit or expansion tank circuit and return it into heater return. Taking coolant from the expansion tank would always be cold coolant and so would extend warmup times as opposed to the heater circuit. With the heater circuit I would be running hot coolant through the turbo and returning it to the engine uncooled. To me that's uncool (pardon the pun). Sooo, that brings me to asking a coupla questions. On the top of the thermostat housing it seems that there is a temperature sensor and also just a simple bolt head. What's going on with the bolt head? Could I plumb the return in there instead? If I could, then it would seem that I would be returning the hot coolant pre-thermostat and so it would be added to the mix and either be cooled by the radiator if the thermostat was open or add to the warm-up time by running back down the bypass. Sounds good to me. The other question then becomes where to draw coolant from. What is the small metal line that runs from the waterpump up to the head? Is it under waterpump pressure? Also, under the exhaust manifold there appears to be a large allen head plug. I assume that is the plug that JimSmith referred to. Can that plug merely be tapped for NPT in the center of the plug? If so, then I believe that would be the easiest route. I assume the plug merely unscrews from the block. Thoughts and ideas are welcome.

Andrew

Noone has any thoughts. Well, I guess I'm the smartest one in the group.:vbac47679

Andrew

That may not amount to much....but, the only caution I would have about mutilating the existing threaded plug is, you have no other really effective "port" for draining and blowing down the coolant system, so, don't make the threaded plug impossible to remove in the process. I would be inclined to just have a special part made with as large a hole in the center as I could fit so the intended flow rate of coolant is not choked off there. You can put an orifice in the line going back to the thermostat housing to throttle the flow if you get too much flow. Not enough and it costs you a turbo. Jim

how are you going to control the vnt turbo??

The I.D. of the holes into the turbo is 5/16" and so I'm sure that will be the smallest diameter in the entire turbo coolant circuit. Also, the turbo is pressure oiled as well and so I doubt even without any coolant flow that the turbo would be destroyed. It might wear out faster, tho, and so I'd like to plumb it in the best way possible.

The turbo conversion and intercooler addition is all being documented in the thread that Forced Induction previously linked to. In that thread are detailed descriptions of the vane control system I will be using and a link to a thread for a VW in which I installed a similarly controlled VNT. Here is another link for convenience:

http://vwdiesel.net/phpBB/viewtopic.php?t=10365

Andrew