more 306td questions

bad driver · Post by **bad driver** » 16 Apr 2004, 00:20

This time I am asking about the coolant system. To the radiator there are 4 pipes that I can establish, the top hose, the bayonet hose from round the side then 2 others, one comes from behind the fuel filter housing, the other comes from the oil cooler. Do both of these flow in the same direction? I noticed on some TD's that I have seen the oil cooler one goes direct to the radiator expansion tank. On another however it connects up to the top hose. My rad only has one fitting on the expansion tank which I know to be the pipe to behind the filter housing. The other concerns me. I want to T it into one of the other pipes but If I T it into the wrong one I may have a huge problem. On my n/a derv this went straight to the top hose so I actually have a hose ready made if it is this way around. If not I have loads of plumbing parts and sure I could make up a T piece. Or is there a way I can check which way they are flowing?

Dave Burns · Post by **Dave Burns** » 16 Apr 2004, 02:43

The small pipe from behind the fuel filter is the degassing pipe and its flow runs towards the radiator, even though it connects to the bottom of the rad, there is a tube inside the expansion tank that travels to the top, the water exits above the water level in the tank and any air is expelled, degassed.
The oil cooler intake pipe, if it comes from the radiator expansion tank to the cooler, goes then from the cooler to the waterhousing at the back of the engine, and flow is in that direction.
If the oil cooler pipe is spliced into the top hose, it then goes from the cooler to the thermostat housing, (which doesn't seem too smart to me as the cooler gets hot water going to it all the time) flow is towards the splice.
What you don't want to do is go from the top hose splice to the oil cooler and from there to the back of the engine, that would put another hot supply back into the block, there are allready two, a third may cause cooling problems.
Where does the other oil cooler pipe on your engine go to.
Dave

bad driver · Post by **bad driver** » 16 Apr 2004, 18:52

ok, This is how I've worked it out, start at the radiator and ther are two hose bottom left, one is the degassing pipe from thermostat housing, then thereis the big bayonet type pipe that runs to the pump, from the pump there are 3 external pipes, one to heater matrix, one to oil cooler and one to underside of thermostat housing, the heater matrix then comes back out to the back of the cylinder head, which in turn goes back through the block to the thermo house, which all makes sense. there is then the radiator top hose which goes from thermo housing direct to top of radiator opposite side to expansion tank. I am then left with one hose coming from the oil cooler which presumably is water coming out of the cooler as the pump is sending in on the other pipe. On my old engine this pipe went straight into the top hose between the thermo and the rad. Effectivley that would be putting it straight back to the radiator to then cool again. On the engine I have got now however it wasnt spliced that way and from what I've seen of pictures when it was in the old car (written off) the pipe went to the expansion tank but on its own fitting next to the degassing pipe. Stupidly enough I didnt realise this was a degassing pipe at the time and had originally t'd the pipe into the degassing pipe so it still flowed to the expansion tank, however this is putting a lot of pressure into the expansion tank even when cold and I think may of been the cause of the blown head gasket within a mile problem I had. I am really looking for a vote of confidence that putting it back to the top hose and effectively back to radiator makes sense. To me it sounds right as that way it is then cooled down again and makes a complete circuit, however the last thing I want is another problem occuring that may result in being more serious than a blown gasket such as buggered oil cooler, cracked radiator etc. Someone else has told me it makes no sense being in the top hose as it would create a back pressure to the thermo hoousing and effectiveley stop the water flowing out of the cylinder head, but I cant see it as the pump is still drawing coolant from the rad therefore creating a vacuum effect that will pull the coolant the right way??
Sorry if I went on one there but trying to give as much detail as possible to get a good accurate response.

Dave Burns · Post by **Dave Burns** » 17 Apr 2004, 00:58

Hehehe....well bad driver, you're a bad mechanic aswell, hehe no just kidding.
You F****D it up big time with the piping though, and that is deffinately why the head got cooked.
The water housing at the back of the block and all its pipe connections are under suction when the engine is running, so any pipe connected to it will have a flow towards it and into the pump, from what you write it is my understanding that you think the flow is in the other direction, which of course is wrong, the pump output is into the block.
What you did by connecting the oil cooler intake pipe (remember the other end goes to the water housing at the back of the block and so has a strong flow in that direction) to the degassing pipe was to supply a source of air directly into the engine, because as I posted earlier the degassing pipe exits inside the radiator above the normal water level, so any suction applied would simply pull air out and straight into the engine, bad luck.
Worst of all is that the air could not get out again but was destined to recirculate through the engine, lowering the water level in the block and head as its volume grew, the air would enter the degassing pipe (which is what its there for) but unfortunately you connected it to a suction source which simply pulled it back in instead of it getting out at the top (inside) of the rad.
And no you can't put the oil cooler pipe to the top hose either as it stands, because the flow is in the other direction (opposit again to how you perceive it) and doing that as I also posted earlier will simply feed another hot supply directly back to the block, which is bound to cause more grieff because that will make it three hot supplies back to the block.
For the turbo engine you really need the specific radiator that will allow connection of the oil cooler intake pipe to the expansion tank, when oil has been round the turbo it gets very hot, so a cool supply for the oil cooler is a must.
You could if desperate connect the oil cooler pipe to the top hose, but the thermostat housing outlet plastic moulding must be changed for the twin outlet version, one being the top hose and the other specificaly for the oil cooler intake pipe, this set up causes flow in the other direction this time which is towards the radiator.
Anything still not clear to you, shout up.
Dave

bad driver · Post by **bad driver** » 17 Apr 2004, 01:31

Well, I think that finall is making a little more sense. I blamee Mr Haynes and his associates for the lack of understanding on the water flow side of things!! there description gives lend to the notion that the cold water is drawn from the bottom of the radiator, into the water pump, then from there into the system as I described earlier. From what you are saying though it is the opposite way around? The twin block bit for the front of the thermo housing to top pipe is not a problem as I can salvage that part from the old engine. having just looked at it though the pipe from the extra exit on that particular section goes to the oil cooler on the side that the pump goes to on the new engine and the side I have currently got extra went to the top hose. So am I right in understanding you that the piece on the end of the thermo housing with 2 pipes, actually allows the coolant to flow in 2 directions?
I am getting more and more confused with this.
Does this sound right then, the water pump actually draws coolant through the large pipe of the bottom of the radiator it the passes up through the block and the head, around the matrix and the oil cooler 9via a thermo housing bypass on this extra piece)where it is then sucked back into the pump (where I thought it was pushing out) and recirculated back through the block etc, and then once it reaches optimal temp it is then allowed through the thermo house past the top hose and into the radiator to be cooled?
Sorry if that makes no sense at all but it sounds feasible to me.

bad driver · Post by **bad driver** » 17 Apr 2004, 02:01

OK I'll simplify what I was trying to say. Have a look at this and tell me if it is right. I know that pipes 1 through to 6 are in the right places on the engine as they were in place when bought and cannot go elsewhere due to sizes / shapes etc. But as I worked out pipes 2 through to 7 all went opposite to this diagram.
http://www.pgacnortheast.co.uk/flow.jpg

Dave Burns · Post by **Dave Burns** » 17 Apr 2004, 02:56

Hmmm....still not clear then...
"I blamee Mr Haynes and his associates for the lack of understanding on the water flow side of things!! there description gives lend to the notion that the cold water is drawn from the bottom of the radiator, into the water pump, then from there into the system as I described earlier."
Thats correct, water goes from bottom of rad and is sucked into pump.
"From what you are saying though it is the opposite way around?"
No I'm not saying that, I'm saying that only some parts of the system have flow in the opposit direction to what you think.
"The twin block bit for the front of the thermo housing to top pipe is not a problem as I can salvage that part from the old engine. having just looked at it though the pipe from the extra exit on that particular section goes to the oil cooler on the side that the pump goes to on the new engine and the side I have currently got extra went to the top hose."
It does not matter which side of the oil cooler the water enters or exits, the result is the same, the only thing that matters is where the water is sourced from and where it goes to.
"So am I right in understanding you that the piece on the end of the thermo housing with 2 pipes, actually allows the coolant to flow in 2 directions?"
No thats totaly impossible, because the small pipe forks of as it does, some of the water flowing towards it from the engine will naturally enter it and flow towards the oil cooler, the rest of the water simply goes along the top hose to the radiator, but because the other oil cooler pipe is spliced into the top hose, the effect of the water in the top hose as it goes past the splice is to also drag water from the oil cooler pipe into the top hose, thus the oil cooler's flow towards the radiator is further strengthened.
"Does this sound right then, the water pump actually draws coolant through the large pipe of the bottom of the radiator it the passes up through the block and the head, around the matrix and the oil cooler 9via a thermo housing bypass on this extra piece)where it is then sucked back into the pump (where I thought it was pushing out) and recirculated back through the block etc, and then once it reaches optimal temp it is then allowed through the thermo house past the top hose and into the radiator to be cooled?
Sorry if that makes no sense at all but it sounds feasible to me."
Nearly, hehehe were getting there, the reason for certain pipes leading back to the engine block is to provide rapid engine warm up from cold, in a cold engine the thermostat is closed preventing water being pushed from the head and along the top hose to the radiator.
The pump is still spinning obviously on the running engine and it gets is water supply by sucking water from the head and through the matrix back into the pump, it also gets a supply from below the thermostat housing, the water recirculates through these pipes back to the block untill the temperature has risen enough to open the thermostat, then the flow in those same pipes is reduced as water is allowed to go through the top hose to the radiator, and up until the the thermostat opens there can be no flow through the bottom hose or oil cooler (where the oil cooler is piped to the back of the block) except for the small amount getting into the rad via the degassing pipe [blue]
[blue]Better stop there as I think thats probably confused you enough for now[:D]
Dave

bad driver · Post by **bad driver** » 17 Apr 2004, 03:36

did you look at my diagram? I think from what you have described I now have it right on the diagram. If so then I'm ready to rock and roll tomorrow.

Dave Burns · Post by **Dave Burns** » 17 Apr 2004, 03:51

Oops just seen your diagram.
With pipe 5 (cooler to pump) inplace, you really need pipe 7 from the cooler to go to the radiator expansion tank, on a turbo engine.
Usualy when pipe 7 (Cooler to thermostat housing) is in place, the other cooler pipe (not shown) is the one spliced to the top hose.
The configuration of the oil cooler pipes as in the diagram is not one I have seen on any pug/cit diesel, that set up will put a 3'rd hot supply back into the block, with the potential to cause overheating at peak loads and especialy so in hot weather.
Dave

bad driver · Post by **bad driver** » 17 Apr 2004, 03:55

Thats what I thought but even when the oil cooler pipe was running back to the expansion tank it was just puting exsessive pressure into the tank, which doesnt make sense to me if the pipe is sucking water not pushing water??

bad driver · Post by **bad driver** » 17 Apr 2004, 03:57

is all the flow in the right direction on the diagram? If it is maybe I can work it from there into a circuit that doesnt put 3rd hot back in?

Dave Burns · Post by **Dave Burns** » 17 Apr 2004, 04:50

Yes thats the way it will flow if piped up like that, it will work but you must keep a close eye on the temp gauge, you will probably find it fluctuates between normal and hot much more than usual.
The actual routing of the pipes can not in its self cause pressure to build up more than normal, except where such routing had caused large amounts of air to be drawn into the engine, then you would have water periodically contacting the hot internal surface of the head producing steam and hence the excess pressure.
Make sure the degassing pipe is totaly leakproof where you have been playing about with it, otherwise air will again be drawn in when the engine is at rest and cooling down.
Dave

bad driver · Post by **bad driver** » 17 Apr 2004, 14:46

Thanks again, you must be the only person that has ever been able to accuratley describe the way the water flows!!
Anyway, one final question. would it work better if I can get the water into the oil cooler to come direct from a 'cold' water supply?
ie, pipe 7 from pipe 1??? I have dabbled in household plumbing beforer and live literally 20 doors from a plumbing suppliers. I could easily have a proper piece made up to take a feed from pipe 1. To me it sounds like it makes sense and would be much more effecient at cooling as it is putting cold over the oil since the piston rods are oil cooled on the turbo diesel.??
My concern with this however is until the thermo opens it is pumping more water into the block and head than it is allowing to flow out, or as I work it out will this be ok as any excess pressure will be released via the degassing pipe and in effect make the degassing more efficient as well?

bad driver · Post by **bad driver** » 17 Apr 2004, 18:15

OK, managed to get a pressure fitment from a local plumbers which is now in the expansion tank in a place to draw fluid from the tank, after cooling and not hinder any other flows. It is now technically the same as the expansion tank with 2 fitments for pipes so should solve the problem. I'm just waiting for the sealent to dry properly so I can test it works properly.

bad driver · Post by **bad driver** » 17 Apr 2004, 23:12

Tested, does this sound as though everything is correct, once the sealent had dried I filled the coolant up again, taking care to bleed the system via the two points on matrix and degassing pipe. I then ran the engine without the rad cap to make sure no water was backing up into the tank as it previously did. It didnt so looked ok. I then ran the engine at avbout 2.5 to 3k rpm to get the temp up. Got to about 55 degrees, the oil cooler pipes were warm, the pipe from under the thermo house and back to pump was warm and the rad top hose was cold. 60 degrees thermo seemed to kick in and top hose got warm, 90 -95 degrees the fanbs kicked in and cooled the temp back down to about 85 then shut off. At this point I let the system fully cool then checked expansion tank, fluid level had dropped about half way so presumably has pushed out any air left in the system and replaced with coolant as no signs of any leaks or white smoke from a blown gasket.
Does this sound like normal operation?? I think it sounds as though it is now running as it should, it took ages to get from 60 to 95 for fans to kick in so it indicates the coolant was working correctly to me and obviously once the car is moving the air flow across the rad should keep it under 95 anyway. Just ned a vote of confidence for normal behaviour before I dare to run it out on the roads again.