VW T4 Forum - VW T5 Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hi can anyone clear something up for me what's the deal with top dead center for removal of water pump?
I have seen people putting the crank into tdc using the tools and swapping the pump out from that position and reading the haynes manual they put it in tdc then turn away from tdc and say not to remove in tdc :unsure:
 

·
Registered
Joined
·
1,881 Posts
There is no requirement to set the engine to TDC on the 5 cyl engines. The pump gear has no alignment marks to replace it in any particular place either. Just take it straight off.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #3
That's what I was hoping for as I went for the suck it and see method when I swapped it , i was wondering why the haynes manual make the statement not to do it tdc. After I swapped it I noticed my bottom hose was cold after a long run in 27° ambient temps could this be an air lock at the thermostat ?the stat works as it should the heater is roasting no overheating issues but only top of the rad is hot and it's not blocked if the gauge is saying 90° and the bottom hose is cold the stats not opening. Don't know if this was pre existing or not.
 

·
Registered
Joined
·
1,881 Posts
Just out of interest I checked the bottom hose on my 2.5 when I went to a supermarket earlier. The air temp was 20 degrees and it was only 2.8 miles. When I arrived the van was only just showing 90 degrees and the bottom hose was stone cold. Another 2.8 miles home and halfway back it hit 90 again and stayed there. On arrival the hose was still stone cold. I was surprised given that the thermostat must have been open by the time I got back. Still, 5 odd miles isn't much for a big old diesel to warm up fully and these 2.5's are known for a bit of a slow warm up especially in winter.

After a very long run the top hose should be too hot to hold on to for very long and the bottom hose cooler (because the radiator will have done its job) but still quite hot. I must admit I never had reason to check mine before. I doubt if you have an air lock as long as the thermostat is opening correctly. Once the thermostat is fully open the whole system should flow freely. Sometimes air locks can occur withing a heater matrix if it is placed high up but it's not a known thing with T5's.

I'd say in summer if your bottom hose isn't very warm after 20 miles something is amiss. Perhaps the thermostat isn't opening properly but the cooling fans and maybe the secondary cooling pump (if it is still actually working!) are compensating.

Here is a link to a pic of the coolant flow and direction. Have a look first though at the pic of the gear train. You can see the the water pump gear is driven off the intermediate gear and that's it, it has nothing directly to do with cam/crank timing. The VW Erwin manual makes no mention of aligning the engine for that job. I think someone at Haynes has got freaked out by the site of all those gears! :ROFLMAO:

 

·
Registered
Joined
·
288 Posts
The W/shop instructions say to have engine away from TDC,
quote "It is only possible to bolt special wrench -T10225- onto crankshaft in one position.
To remove the coolant pump, the engine must not be at TDC."


I don't know why, but might be to do with that special wrench -T10225 - which I assume is to counter hold while undoing the water pump gear nut.

182404
 

·
Registered
Joined
·
79 Posts
Perhaps the gears that drive the camshaft can move a fraction and if the piston is at the top of its stroke there is a small chance of damaging a valve. I seem to remember a little play in the gear train before the pump gear "locked".

My bottom hose never gets warmer than ambient and usually somehow feels colder than ambient. Top hose gets hot quickly and the van never overheats.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #7
Thanks for the imput every 1
T5tdi it was hot and the run was mostly up hill fans could be cooling it down but the pipe should show some sigh of heat as stat starts to open at 87° there is a sizeable difference between what the gauge is saying and what the engine is doing but that's not too say the fans aren't compensating.I dont have vag com so cant tell the true engine temp thanks for checking yours though.

Osty that does make sense.

Benny I am probably being paranoid as I have never checked the bottom hose in the 15 years I have had the ermm pleasure of owning it😆

I have a lot of miles with near full load on next week;) so have taken the stat out and blocked part of the rad off with cardboard. I have an airlift vacuum tool on loan for next weekend then it's full flush stat back in and see what happens.
 

·
Registered
Joined
·
1,881 Posts
Well Mea Culpa! Thanks to Osty for pointing out that the manual does say that the crank lock tool sets the crank away from TDC and apologies to Haynes for poking fun. :p I think that Bennymassive has the correct reason for it. I confess that I have never used the crank locking tool for a water pump change and always used the old school 'brakes on 4th gear' version to undo the pump nut. This avoids the need to remove the under wing panel and other stuff. In my defence, my way does preserve the gear relationship so you aren't locking one part while allowing another to turn so you aren't actually taking much of a risk, although you must still tighten the pump nut properly if you are using this method.
 

·
Registered
Joined
·
1,881 Posts
Next time I do a longer run I will remember to check the bottom hose temp afterwards. I never have the belly pan on and still have one of those infra-red temperature guns so perhaps we can confirm some 2.5 numbers here rather than my crude hand hold test.
 
1 - 9 of 9 Posts
Top