Conversion coolant issue

[skids]

Hello,
I am currently converting my 300tdi Defender to ex perentie 4bd1t and am having trouble with my cooling system. I have kept the 300tdi header tank and cut the bottom radiator hose and teed the large hose from tank into it and obviously the small hose from tank too top of rad. As it sits now the top of my thermo housing is exactly the same height as top of header tank.
The air lock in thermo I can get rid of each time through the fitting on thermo block but comes back everytime I shut down. All hoses are hot except the bottom half of the bottom rad hose which is cool to touch between rad and tee. Fluid in header tank is also cool to touch. Both the water pump and thermostat are new, thermostat opens in boiled water.
Will I need to convert tank to a recovery system as I'm thinking as both header tank and thermo housing are the same height this is causing air to get into system. Also on a 20min drive at 90kmh temps on vdo mechanical gauge never got above 75deg, only after turning engine off did gauge go just above 80deg.
Any help appreciated, cheers, paul

[rijidij]

Was your 20 min drive in cool conditions, 75deg sounds pretty normal, even though the thermos are 82deg the Isuzus take a bit of work to get hot.

[skids]

Ye a pretty cool day in Perth today. I have noticed the fan sucks a huge amount of air back through radiator so I have a viscous fan set up ordered to put on later. I'm a bit hesitant to drive much further and pushtemps up until I can sought header tank/air lock issue out.

[Dervish]

My setup is exactly the same as yours except the tank must be higher? I fill the system via the tank with the thermo housing plug out then replace it when it starts to spill out and it works perfectly.

[Phil B]

I had a similar issue with my County with 4bd1t
I was using the plastic (Disco1?) header tank with the one large and one small pipes. Kept getting air locks.
I changed the tank to the copper single small pipe tank from a Perentie plumbed to the top of the radiator in the same way as the Perentie. Problem solved.
Sits on 82-85 deg all day now once it has warmed up.
Also I found that the header tank needs to be as high as you can get it so that the half way water level is higher than the heater inlet pipes.

[steveG]

My setup uses the 300tdi header tank, with the bottom outlet connected to the thermostat housing. No tee in the bottom hose.
Small hose from the header tank connects to the top of the radiator.
Its done some pretty hot/heavy work and never had an issue with cooling.
I'll grab a photo the next time I'm out in the shed.

Steve

[skids]

Cheers guys,
I took it out for over an hour today, same thing couldn't get it over the 80deg mark. All hoses except heater hoses cool to touch. I think I'll give Steve's suggestion a go, if no luck I'll try and chase down a perentie single hose tank.
Good news is egt's didn't go above 350 so plenty of room to play with when coolant sorted.

[steveG]

Photo as promised

https://uploads.tapatalk-cdn.com/20190810/ec0388cc59a453560b59b3c55ebbaa73.jpg

It's not a perfect setup, but has worked well for the last 7 years, 100K.

Steve

[skids]

Thanks Steve,
I bought barbed fittings this morning, so just have to wait for new bottom house to arrive and I'll give it a try. Does this set up allow you to run tank at half full to allow room for water expansion? My tank is virtually full to get coolant at top of thermo housing, which leaves no room for coolant expansion. Maybe only 10-15mm available to lift tank before it hits bonnet.
Cheers

[rar110]

Skids, can I get the part numbers for a viscous fan set up? Thanks

[steveG]

Thanks Steve,
I bought barbed fittings this morning, so just have to wait for new bottom house to arrive and I'll give it a try. Does this set up allow you to run tank at half full to allow room for water expansion? My tank is virtually full to get coolant at top of thermo housing, which leaves no room for coolant expansion. Maybe only 10-15mm available to lift tank before it hits bonnet.
Cheers

Yes, I just run the tank half full so plenty of room for expansion. IMO its not critical to have the tank coolant level above the thermostat housing. When I first converted mine I messed around with bleeding etc, but these days if I've broken into the cooling system I just remove the plug in the top of the radiator and fill the system up via the tank until it starts to come out the radiator, then refit the plug, fill the coolant tank to about half full and drive it! Check and refill again over the next few days until it settles down.
They are a dinosaur of an engine and not sensitive about the cooling system like a 300tdi etc.

Steve

[skids]

Cheers steve