Club 80-90 Forums

I'm bringing my old thread on this problem over from Electrical (I originally thought the problem was with the radiator fan wiring)

https://club8090.co.uk/forum/viewtopic.php?f=39&t=133689" onclick="window.open(this.href);return false;

I have concluded that the fan is working properly and I now think that maybe the real problem is the coolant is not recirculating through the system.
The system has been thoroughly bled, new (tested) thermostat, new water pump, the radiator has been pulled and flushed (flow seems real good), and it does get hot (slowly) The cabin heating system is getting real hot, real quick.

So…what I'm now thinking is that the main hose from the head to the main plastic pipe might have some restrictions. I have read that there are inserts in the hose that restrict coolant flow to the expansion bottle and the oil cooler. I can feel these at the hose junctions.

My question is, if these are plugged can it restrict the flow enough to prevent coolant from reaching the radiator in an efficient manner?
It seems to me that if the main hose from the head has restrictions then more coolant would be forced into the smaller feeder hose which goes to the cabin heating system (which would account for the cabin getting so hot, so quick) and less would make it to the radiator and cause the hot engine problems I have.

The engine is getting hot enough for the Aux water pump and turbo cooling fan to run after even a short drive, but the radiator is not even warm. If I run the truck long enough the radiator does get hot, I can feel the temp rise across the rad and up and over to the return side.

This hose is very expensive and mine seems to be in good order, but if it is clogged at the restricters can it be cleaned?

I have ordered a new radiator and a cooler radiator temp switch: http://www.busdepot.com/25195948175" onclick="window.open(this.href);return false; and will drain (again) the system when they arrive, but wanted to ask for opinions before ordering a new hose. http://www.vwheritage.com/vw_spares_Wat ... tartRow=23" onclick="window.open(this.href);return false;

Well...I replaced all the hoses...still overheated!replaced the rad FIXED!! so.

When I replaced the head gaskit (over heating caused it to fail) I also replaced the rad and the thermostat with and the main front to back pipes as the rad was damaged and the inserts in the pipes were projecting from the nylon pipes.
All was good upon the start up but I could not get it up to operating temp the problem was the stat was not operating correctly, not letting the hot water flow to the rad (stuck closed) so I bought a new one directly from vw (so oem). As I had power steering it's a bit of a pain in the ass to change the stat having to remove the p/s pump taking a couple of hours rather than half an hour. Would be the first thing that I would change as it only costs about £10 for a genuine stat.
I would be very surprised if there were a blockage that could restrict the flow of hot water.
Neil

Well, here's a follow up on this problem.

Still running hot enough for the turbo cooling fan and aux water pump to come on after each drive.

Brand new Behr radiator and a new lower temp rad fan switch. I also removed the main hose from the block to the coolant pipes and checked all others, no blockage.

I'm at my wits end with this overheating! The next thing I'll try is diluting the coolant. I'm currently running about a 60/40 mix (where we live it gets down to -30) Maybe I've got too much coolant?

I will try to source an oil cooling setup. Unfortunately BW won't ship to Canada. Maybe someone could point me towards another oil cooler setup I can source here in Canuckastan?

Have you actually physically checked that the water pump is rotating in the correct direction? Several people have found that they overheat due to running the belt on the wrong side of the pulley. As far as I know there are no markings on the pumps to show direction of rotation so you have to take it off to check. (Or run it with a belt on the opposite side of the pulley to test it) I had 3 water pumps in my shed - 2 were one direction and 1 was the other and they were identical to look at externally.This catches people out quite often with an engine swap.

The truck has the V-belt pulleys and so needs a clockwise pump. The one I installed is a Seleri. It has the stamped vane instead of a cast one but otherwise is very well made. Seleri on the left, China made Meyle on right.

http://images.thesamba.com/vw/gallery/pix/1231395.jpg" onclick="window.open(this.href);return false;
http://images.thesamba.com/vw/gallery/pix/1231397.jpg" onclick="window.open(this.href);return false;

Not sure whether the different vanes make a difference but the truck had the same overheating issues before I changed pumps. (original pump has cast vanes in a clockwise pattern)

In this pic you can sorta see the setup.
http://images.thesamba.com/vw/gallery/pix/1229338.jpg" onclick="window.open(this.href);return false;

That certainly looks correct to me.
I have just read your other thread and it appears to me that your main concern is the running of the auxiliary water pump after a run - that is what it is supposed to do to remove the excess heat that would not dissipate quickly when the engine isn't running. It would run after a short journey also as the thermostat wouldn't have opened fully and all the heat will be contained in the engine. I can't see that you are having any problems with overheating as such in your posts like gauge going high, boiling coolant, etc. What exactly do you mean by "overheating"?

The turbo cooler/aux pump comes on even after an easy drive (long enough for the thermostat to open), others talk about their aux pump and turbo cooler rarely coming on at all. It seems to take a very long time for the radiator to get warm then hot and even with the new lower temp fan switch the rad fan rarely comes on.(why I was thinking blockage) I have a IR gun and have followed the hot water through the system. Pipes in the engine compartment are in the 90's + and the rad at 80.
Temp gauge is always at 5/8ths to 3/4 and the engine is obviously hot. The cabin temp screams heat!
I have been careful about driving it for very long or hard, I don't want to fry a fairly new engine. (brand new long block 2012)
If I had not just replaced the water pump I would think it's not pushing the water around the system adequately. Wondering if maybe the stock water pump may not produce enough head to move water around the Vanagons vast cooling system with sufficient pressure. There is obviously enough cooling capacity since the radiator is not getting very hot. Maybe an electric coolant pump?
Everyone talks about adding an oil cooler to AAZ's, maybe a aux coolant pump plumbed into the main system would be better.

E D I T: While looking into the electric coolant pump I came across this post, some interesting reading.
http://www.thesamba.com/vw/forum/viewto ... water+pump" onclick="window.open(this.href);return false;

There is some talk in there about the thermostat not getting a steady supply of hot water to keep it open. The diesel engine layout does have a hot return line from the header tank to the water pump?

From the post:
"- So here is my theory:
With the Audi water pump not having enough head (pressure at the pump outlet) at lower RPM, the engine is basically overheating at idle due to lack of coolant flow. Once the coolant temps reach 272F, the thermostat finally opens. However, the coolant in the system is stone cold and there is so much coolant volume that the thermostat quickly closes back up. This cycle happens over and over again when the engine is at very low RPM. At higher engine RPM, the pump creates enough head to keep the coolant flowing fast enough that the coolant temps in the entire system stabilize which keeps the thermostat in some state of open. This allows the coolant to continue to flow through the entire system, thus keeping the coolant temps in check. Once the engine RPM drops, the water pump can’t flow enough coolant and the observed engine temps start to rise. Only when the engine RPM is increased does the coolant temp start to drop due to increased flow. To prove this theory, I removed the thermostat, with the thinking that the thermostat adds some restriction to the system, even when open, and that without that restriction, the pressure drop in the system is reduced and the pump should be able to flow more freely. Sure enough! With the thermostat removed, the system never once showed the high temps at idle. Granted, without the thermostat in place and the ambient temps in the low 40s, the overall coolant temps were way down, so temps through the heater circuit were low as well. I think that proves that the culprit is the increased pressure drop (backpressure) in the system compared to the stock Audi system and the water pump’s inability to cope with it."