RODS build........

[andyrennison]

Its Alive! Great to see it out and running Rod

[ROD]

So bit of an update...
After succesful mot last week, Ive been holding off getting the road tax to save wasting 3 weeks of this month.Sunday being the first of the month, Im taxing it to be used from then.Been doing a few bits on it while I wait.
Testing of the new raised up rad set up will begin on Sunday with a few cautious runs round the town, returning after each circuit to check everything out.Then its driving the same route that I used previously down the bypass when it kept overheating.A bit hard to check it thoroughly as the weather is much colder, and I am only putting the first few miles on new barrels /pistons and bearings, so keeping speed down.At the moment , the temp hasnt climbed past a reliants normal running temp, so thats a slight glimmer of hope! Im praying it will keep cool and the coolant wont pressurise etc as it did b4.Will keep you posted.Ya never know, I may have solved the most expensive lesson Ive ever had in years of engine swapping.

[Manky Monkey]

So- to re-cap, the overheating & spitting coolant out of any available orifice was basically down to the radiator being mounted lower than the highest point in the water system on the engine? So raising the rad' has cured it? Have you still got the header tank fitted?
Presumably sealing the rad with a cap that doesn't have a sprung seating to allow water past when it reaches a certain pressure, & fitting a header tank somewhere convenient on the frame but higher than the rad would work? Or just fitting the rad as high as possible to start with.
I'm asking cos it sounds like Mr Twisted may have the same problem, but I've never had it on my own builds. I'm guessing that was more by luck than any shrewd engineering knowledge on my part. I genuinely do have a terrible memory, but I vaguely recall the Flapster doing it once or twice, always when slowing down after a long fast blast. So mounting the rad as high as you can is the answer?

[ROD]

The header tank set up was only part of the experimental process.I removed it cos it didnt make any difference, looked ugly, and yes I was running a blanking cap.i have now fitted the rad in a more vertical position, couldnt get it at exactly the same height as the orig reliant engine bay, so have fitted around an inch or so higher.have also fitted an expansion bottle so that I can see if it is throwing coolant out.I have commented on twisteds thread re this, cos im wondering if his rad is too low.i remember you said that one of your trikes did spit water after a run.yes, the rad was too low by about a couple of inches.when the coolant got hot and expanded , it dumped it out the overflow.there was no expansion (air)gap in the radcos it wasnt the highest point of the system.in fact the highest point was the back of the head.a filler in the top hose (highest point)would have helped, but it wouldnt have allowed a large enough empty area for expansion, hence I tried the header tank system.Ive also now fitted a couple of bleed areas in the system to aloow air to bleed out when filling, plus I use the fifer system for filling.
so in summary..coolant heats, expands, dumped out of overflow into exp bottle, bottle overflowed, dumped onto road(and my left leg!).loss of water caused high temps.on head removal I found strange(poss water marks)in one bore, but headgasket had no blow signs.

[kapri]

Only fill the rad to just over the tubes.  The water expands as it heats so will always try to push the cap if there isn't enough free volume inside for that to happen. The throwing water out after a run is the same thing but caused by 'heat soak' ie soon as the water stops moving all the heat in the block transfers straight to the water and it expands very quickly.

Once you've filled it run it up with the cap off to working temperature, top up to just on the tubes and you should be good to go ( hopefully!!)

[ROD]

Yeah, I agree with all that Kev.Fifers way of initial filling is to disconnect a hose from the w/pump andtop up down that tube, allowing air to bleed out.This is great and works fine on a normal system,but if the rad is lower than the thermostat housing, it will top up the whole block and rad, right to the top of the tube youre pouring it down.the whole system is full, but will start to drain at the lowest point (rad overflow) as the water expands.It will drain out and not be replaced , causing an airlock (poss steam pressurising ??)therfore high points of system (head etc) will only have water minimally circulating from whatever the water pump can throw up there.whew!...Hope that describes it.

[Manky Monkey]

I used to fill my coolant via the bottom rad hose too, then top up at the filler cap & run with the cap off until the engine was warm. The couple of trikes I built with rear mounted radiators needed filling with the rear wheels up on ramps, with the rad cap off. Eventually the air would travel to the highest point & burp itself out of the filler.
I had a bleed valve at the highest point in the system on my first green one, consisting of a motorcycle brake caliper bleed valve screwed into the side of a short length of steel tube. It was spliced into the top hose between the water pump & the back of the head & bled like a household radiator -run the engine up to temperature then crack open the valve to let the air out & close it when it starts spitting water. Worked fine. My red, rear radiatored Reliant, (try saying that after a couple of pints), had similar bleed valves in the top of each frame front down tube.
Never had this problem with my own builds, but as I said, probably more by luck than judgement. Flap's orange 'un did it very occasionally & always after rapid deceleration after a ..."spirited" ride. Maybe his rad was just on the point of being too low, but fine most of the time. I always mounted mine so that the top hose, from the rad to the 'stat housing, was horizontal, just cos it looked best that way. I guess that automatically set the rad at the right height.

[ROD]

Today Ive been testing, testing, and testing , up and down the bypass.I purposely didnt run the rad fan (bike type on front of rad), to try to match the conditions of the previous tests in 2013, when the weather was warmer.As far as I can tell, the temp only climbed(to 100degs) when I was in 4th gear climbing a gradient, when the engine was labouring, as it likes 3rd gear nearly all the time, due to larger diam rear wheels.Im guessing the temp would be slightly lower once the engine is run in.In any case if I pulled into a layby, the temp started to drop with the engine stopped.I generally travelled at 45/50 mph, a couple of times up to 60. No coolant ejected from the rad overflow at all.So my summary is it looks as though itsgoing to be ok, but I will do the same tests when the weather is warmer.

[merv]

That sounds like good news Rod, I'm really pleased for you 

[Manky Monkey]

That's great mate. Useful info for other budding builders then -keep the rad up high!

[hunter]

Sounds good Rod.

[scannerzer]

good stuff Rod ,glad it's worked out

[twisted]

great news rod. happy that it looks like you have got it sorted. done mine to and all looks good (see post on my thread  )