unusual cooling tank set up req help

3500 VWt25 · Post by **3500 VWt25** » Tue Sep 08, 2015 8:26 pm

hi people,
im looking for some help ,
ive fitted a 3500 su into the back of my t3 <t25> vw pick up and am looking for help and advice on the cooling system
my rad has only two pipes coming from it one at the top another at the bottom I dont have the skinny pipe that goes to the top .. ie for bleeding

ive drawn a diagram of what I have can one of the gurus have a peek and tell me the best way to pipe its im running without a thermostat and without heater marix for now until ive gained trust the engines good
my rad has a bleed screw at the top

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Thanks for looking and I appreciate any help

kiwicar · Post by **kiwicar** » Wed Sep 09, 2015 10:02 am

Hi
I would not run without the thermostat, the system is designed to run with one and will have hotspots in the heads and block if you do not have one. you also need some form of expansion tank or method of relieving pressure but still getting water back into the system as it cools. A T piece in the top pipe and a small tank with a pressure relief valve will do the job. I would put a short bypass pipe in place of the heater matrix, don't just block the pipes, again this will stop hot spots forming. Otherwise looks like a good plan.
best regards
Mike

ChrisJC · Post by **ChrisJC** » Wed Sep 09, 2015 6:00 pm

You definitely need an automatic bleed at the highest point of the system. Otherwise you'll be bleeding it all the time.

Can you get the rad modified?, or maybe T into the top hose right by the top entry into the rad?

Chris.

v8250 · Post by **v8250** » Wed Sep 09, 2015 7:13 pm

OP, that will be one great conversion when done. As an aside, hope you're not going to keep that crankshaft pulley on your water pump? It'll muller the pump bearing...maybe try a lightweight alloy one from MGOC Spares, Clive Wheatley et al. Good luck with project...

SuperV8 · Post by **SuperV8** » Thu Sep 10, 2015 11:52 am

Looks and ace conversion.

Looking at your photo one point that might me useful is that the sierra cosworth oil filter fits the rover V8 which is a lot shorter, may help with your packaging.

Tom.

Eliot · Post by **Eliot** » Thu Sep 10, 2015 3:59 pm

There should be a small outlet at the top of the SU manifold between the two carbs - that should be connected to the top of the radiator to bleed the air.

3500 VWt25 · Post by **3500 VWt25** » Sun Sep 13, 2015 9:30 am

thanks for all reply and info ,
im running the van as is for now ,
ill be changing to the other type of water pump in a few months ,
and a remove filter housing

ive tried all sorts to get this set up to work with no luck

what's the best bet ?
a jap type header tanks or a standard type found on newer cars ,
im struggling with header tanks at the moment most are awkward shapes the best ive found so far ''laughs'' is a mk2 clio tank

obv with my rad been up at the front of the van and not having the bleed point
can some one show me a digram without the bleed point
cheers craig

3500 VWt25 · Post by **3500 VWt25** » Sun Sep 13, 2015 9:31 am

the small pipe that comes from the su's could it in therory be connected to the top part of the header tank ?
the header tank has two main pipes coming off it
and a smaller one at the top

ChrisJC · Post by **ChrisJC** » Sun Sep 13, 2015 12:17 pm

If the rad is at the highest point, at the front of the van, then I would put the header tank there too. I would use a pressurised header tank, with the bottom (5/8ths approx) pipe going into the rad bottom hose, and small bleed hoses coming from all the high points, i.e. a small T into either the top hose or the rad itself, one from the top of the inlet manifold, and maybe one from the heater matrix if that's at the front. I realise you will need a bleed from the top of the inlet running all the way to the front.

Ultimately you will have to experiment, but you definitely need all the high points going to the header tank which has to be higher up.

Chris.

Ian Anderson · Post by **Ian Anderson** » Sun Sep 13, 2015 4:13 pm

Chris
I would do the exact opposite as we do with GT40s

In your engine bay you have loads of space above your engine and to the side to put in a header tank and take the 5/8 pipe to the return from radiator side of the main coolant route.

You actually do not need to continuously bells the radiator. Trust me I have one and once a year I crack the bleed on the top of the radiator and coolant comes our - no air, but it does take a bit of bleeding to get everything out.

After that you have an engine bay like any other car and just connect up as normal. Remember any bleeds back to the header tank should be small so as to restrict water flow thereby forcing it all through the rad

Ian

3500 VWt25 · Post by **3500 VWt25** » Sun Sep 13, 2015 8:34 pm

Again appreciate all your help
The bus was originally made air cooled vw added the rad later on and sort of made it fit its got two main pipes coming off it on the same side one at the top one at the bottom and a bleed valve on the very top
theres no space up front for a header tank at all
Ive bought a new tank off evil bay
Can one some one tell me how to pipe it in please
ive bypassed the heater matrix on the back of water pump for now
I have 2 pipes on the engine two pipes on the rad and a header tank with two pipes

unstable load · Post by **unstable load** » Sat Sep 19, 2015 6:09 am

What about a Mini or SD1 header tank? They are quite small and unobtrusive and can be tucked in a corner.

Darkspeed · Post by **Darkspeed** » Sat Sep 19, 2015 10:09 am

I like using Volvo 240 740 etc. round or rectangular type expansion header tanks. Just two fittings a lower larger expansion connection and an upper small bore air bleed.

You plumb the bottom - expansion - outlet to as close as possible to the water pump inlet and you fit a small bore air bleed to a tapping at the highest point in the engine / inlet manifold. The engine must be fitted with a rise to the front to encourage air into the point where the bleed is taken from. I would fit a 74/75 C stat and drill a small 4mm hole in its upper edge.

This installs the expansion tank in the correct position of always being between the lowest and highest pressure points in the system ensuring the best air elimination.

ETA

If you wish 100% correct installation fit the tank at a level where the -MIN- line is at least level with the top of the thermostat housing and better a little above.

Darkspeed · Post by **Darkspeed** » Sat Sep 19, 2015 10:20 am

For a bit of extra info - the water in the system will expand around 4% volume in operation and being in-compressible you have to make room for it somewhere. So if you have an 11 Litre system you will need an expansion tank with a 440CC capacity.