2.4DW in VW LT - Overheating on short runs - no load

[ngoma]

Originally Posted by v8volvo

The more conclusive, direct test you can do to confirm the integrity of the WP impeller (without having to take the whole front of the engine apart to remove the WP) is to remove the thermostat again and look in towards the front. From the tstat opening you can see the backside of the water pump visually (might need a small mirror), and with a screwdriver or piece of bent rod, you can also reach in there and see if the impeller is loose. If you are able to spin that impeller while the engine is off, then you have found your issue.

Brilliant! Could probably also see if the impeller vanes were corroded into nothingness.

[v8volvo]

Originally Posted by ngoma

Brilliant! Could probably also see if the impeller vanes were corroded into nothingness.

No credit here for that idea, it's a common (but I agree very clever) procedure in the TDI world on the 1998 and up engines that very closely imitate the old D24 block architecture with internal TB driven water pump and tstat located just behind it. Those all came from the factory with plastic impeller pumps and they suffer from spun off impellers all the time, very high failure rate, so those guys are having to worry about this frequently, hence the check procedure they came up with, which luckily for us works on a D24 too. It seems like the plastic impellers on those little pumps are especially fragile, the D24 design (plastic or metal) is much beefier.

I have only ever seen firsthand one D24 water pump with a plastic impeller -- which I installed as an experiment around 10 years ago in my 760 TD, still working fine now. Much more common seem to be stamped or cast metal ones. So I would be somewhat surprised if the OP's van in this thread ends up having a plastic one. But it's possible, especially maybe more so overseas where they could be more widely seen. I think Tom Bryant has found one or two with plastic also. Then too, as you say, it if's metal it could have vanes eaten up by corrosion, or in theory one of those could also spin loose.

[ngoma]

Originally Posted by v8volvo

Then too, as you say, it if's metal it could have vanes eaten up by corrosion...

That would be surprising to me now, after seeing the pristine condition of the original t-stat.

Currently we don't have enough data to make a good diagnosis. We'll know better after blix99 reports the results from:
Heater circuit flow test
IR temperature readings
Entrapped air purging
Impeller inspection

We also don't know the length of time of the reported testing-- may not have been long enough to even bring up temps to open the t-stat.

[blix99]

Hey guys. Sorry for radio silence on this for a while. I really appreciate your input. I have been trying different things to solve this. Taking out the tstat isn't the problem. It's continually draining / refilling the coolant, which is a real, time consuming pain.

So, I had intended to do change the WP and timing belt anyway but this issue forced my hand into doing it sooner than expected.
So, I started this yesterday.
The bad news is, the old WP seems fine and also had cast metal impellers, so not sure after all this that my overheating issue will be fixed.

However, I have encountered another issue with putting it back together. I can move this to a different thread if it's best but will mention it here first:


Timing the 2.4D DW engine 1983 - TDC and cam
So, regarding the timing belt change. I had to remove the front cam pulley to change the WP. I'm not sure it was set correctly to begin with so want to double check the alignment now - how do I set the cam to TDC when the crank is set? I've lined up the TDC marks on the flywheel for the crank but can't see any discerable way to accuratley set the cam. The only marks i can see is on the rear cam pulley, which drives the injector pump belt. This has a 'V' cut in it. If this pulley has a woodruff key, then I assume this V is supposed to also be TDC for the cam? Is this correct? The two front cam lobes (for cyl 1) are both at the top; symetrically opposed, at their furthest point from the valves, which seems right for TDC but I obviosly want to get it exact. The only mark I can rely on is the TDC on the flywheel.

This will also mean re-timing the IP, which I had done before. Just have to reaquaint myself with the procedure from my other thread : )

[blix99]

OK. I took the end sprocket off of the cam; the IP end. This end of the cam has an offset slot. This is where the VW locking tool goes. I made own just now and I assume when the crank is TDC, the locking tool should be inline across the top face of the cylinderhead (with the cover removed)
This seem to coincide with the no. 1 cyl cam lobes being symetrical at the top, so I hope this is all set up OK. A hand turn of the flywheel a couple of times and all seems to be OK.

Are my assumpations correct?

[ngoma]

Correct, very good, with one additional detail:

(From Greenbook) "Insert a 0.2mm (0.008in) feeler gauge beneath left side of tool 5190 to compensate for timing gear clearance."

By left side of tool 5190 they mean the IP side. The feeler gauge gets shimmed between the tool and the top surface (valve cover mating surface) of the cylinder head. At the "corner"

Camshaft front sprocket bolt torque is 45 Nm (33 ft lbs). Use the sprocket holding tool when tightening.

Keep your old WP as a a spare. Did you get the Audi 5-cyl (overspeed) version?

[blix99]

Hello. Thanks again for the reply and advice.

I actually followed my assumptions and have put it all back together and retimed the IP too. All seems to run like before and it didn't blow up on the test run ; ) which is always a plus

I think the new WP was just a standard replacement. I don't intend to do it again any time soon but a part number for the 5 pot audi WP would be useful, in case the memory of this job fades and i decide to do it again : )

Anyway, It didn't over over-heat but it still ran hot. I still need to get an IR thermomenter as I do appreciate this will help greatly with diagnosis. All pipes get hot except the large feed pipe from the rad to the thermostat. However, the top of the rad did get hot after a 10 min drive (which it didn't seem to before). This drive might not have been enough for total running temp but the gauge went way past the middle of the gauge, which is assume is around 90 degs (the middle, not where the needle pointed)

However, the part of the rad that was hot was the top right (looking from the front of the van) which is the opposite side from the feed and above the return at the bottom, which was cold.

I'm going to put some cooling system flush though shortly and give it a better run, then drain this and renew all of the coolant.

I'll let you know how i get on.

ps. Just something I noticed whilst timing the IP - the sprockets on the end of the IP and cam are the same but the cam one is the opposite way round, so the lip is on the inside, towards the engine. Is this right? Seems to run OK but also seems odd that it's not it's own part?

Thanks very much again for your wonderful help and insights.

[ngoma]

Originally Posted by blix99

I think the new WP was just a standard replacement. I don't intend to do it again any time soon but a part number for the 5 pot audi WP would be useful, in case the memory of this job fades and i decide to do it again : )

This is the WP with the slightly overspeed pulley:

https://www.brickwerks.co.uk/t4-part...t4-aab-96.html

Originally Posted by blix99

ps. Just something I noticed whilst timing the IP - the sprockets on the end of the IP and cam are the same but the cam one is the opposite way round, so the lip is on the inside, towards the engine. Is this right? Seems to run OK but also seems odd that it's not it's own part?

Yes you are correct, the rear camshaft sprocket and the IP sprocket are the same part, installed in opposite orientations.

[blix99]

Thanks for ther link. Out of stock on Brickwerks but I'll keep an eye on it.

OK. The saga continues to waste my time. I have so much other stuff to do on this van, the overheating is getting me down as i can't work it out

I've taken everything to bits so many times now. As mentioned, it's not the dismantling, it's the constant draining / refiilling of the coolant.

So, this is how the cooling system in my van works. The rad is at the front of the engine, more or less upright. It actually sits at an angle, with the bottom more towards the front of the van.

The expansion tanks sits directly on top of the rad, which is more or less the same level as the rocker cover.

The whole engine is at an angle, left to right, with the rocker cover more towards the left side of the van, when viewed from the front.

The only exception in this diagram is that the expansion tank (4) shows a dashed circle within the rad entry / engine return line. I assume this signifies the access to allow the coolant into the system. This isn't the case (unless it's there and completly blocked?). This tube in the ET is simply a pass through and the holes are actually in the other through pipe, returning from the heater (1 - I've marked with two red dots) Therefore, this is how the system fills up. These are clear when I've blown through them.

The rad return hose (marked with my wobbly red line) always stays cold. The rad seems to get hot at the top, mostly where I've marked with the red 'circle' (I'm not a good drawer with a mouse : ) but not at the bottom at all.

All other pipes / hose (to heater and around engine) get too hot to touch.



I bought some car rad flush / cleaner yesterday, which I added to the coolant then drove for maybe 30mins. Temp seemed to reach just below the overheat marker and, as mentioned, the hose to the tstat remained cold.

The cleaner seemed to make little difference - coolant is always clean and clear from the first time I drained it.

Any ideas? If it was air in the system, how much would this affect it? There only seem to be a couple of places it could sit, unless it's inside the block?

Thanks in advance for any insight.

[blix99]

Also, in the diagram above, No. 5 isn't there either unless it's part of the hose? This section is all one molded , rubber part.

Also, when filled up and running, all hoses seem to be full. They all seem to affect the coolant in the expansion tank when squeezed.