v8 coolant system

[wooly350i]

Hi all,Can anyone throw some light on the use of a small coolant pipe connection on top of the v8 lump front nearside, at present mine is connected via silicone to one of the bottom header tank connections, I'm asking coz a mate reckons its connected wrongly to the tank, he thinks it just needs to be plugged off. Reason I'm in doubt is because the original temp gauge in the car does funny things when driving ,ie, suddenly starts to rocket up to 100 and even 120 degrees before falling back quickly to a reasonable 80 degrees and less Luke there is an air lock causing it.
As it is connected to the header tank along with two other pipes I'm thinking there could be flow through that pipe and dragging air in from the top of the tank, the engine is fairly modified but the cooling should be he same hopefully, thoughts welcome please.
Had a good blat out in the old git yesterday evening and the motorway cruising was fine, the temp gauge issue occurs when slowed own or in traffic, next week Im booked in on a set up session at Surrey rolling road so it would be good to get some views. Cheers for now,wooly.

Edited by wooly350i on Thursday 17th April 09:35

[wooly350i]

Morning Mark, I think you are correct about water jacket on plenum but mines been disconnected for a long time now, just unsure what to do with the block connection now, the temp rise us alarming although I don't think its a major problem as things seem to run fine and it doesn't blow water out the overflow.

[wooly350i]

So if one outlet from plenum jacket went to the block connection where did or does the other plenum pipe go to?

[wooly350i]

Can anyone else help with original plumbing layout especially around plenum water jacket pipe routes,?wooly

[wooly350i]

Thanks Jon, I was thinking that's how it was but wasn't sure, hence reason why my pipe goes from top of block straight to tank and cutting out the plenum. I may try just blocking it off with a manual vent and see if thermostat in car behaves differently.

[wooly350i]

I'm just wondering as the pipe goes straight back to the tank now there is obviously flow through it via the tank and maybe the pressurised air at the top of tank is getting pushed back down the pipe to top of block where it then creates intermittent air collections thus I get this occasional high reading on the temp gauge before it then quickly falls back after say 10 seconds give or take, its like flying an old Lancaster bomber having to watch the gauges all the time, makes you feel alive
I'm gonna block it off sometime over weekend and experiment.

[wooly350i]

Kenlowe fans and their control pack which includes two relays,fuses and switch temp adjustment screw plus I've got the over ride switch too, all of which are independent from the original temp sender unit and gauge, talking of high points on the block I'm assuming the air would be able to shoot up the main thermostat housing to the silicone/rubber elbow and with a bit of force to the swan neck cap/vent.
If plugging the connection works I suppose the alternative option to prevent backflow from the tank would be to pop a non return valve on that line so at least air would travel towards the tank.
Off to work now, so laters

[wooly350i]

Thanks for the input everyone, useful bit of info there as well martin,cheers. Wooly.