Backflush coolant system, changing thermostat:advice sought

[mikeonb4c]

V. sorry to be re-visiting this. I'm at work and dont have my password for the Members Area. Nor can I find the advise Peter Humphrey (Ithink) gave earlier. My questions are:

Given basic facilities (garden hose, Bongo on the drive), what is the exact procedure for backflushing the coolant system (to include radiator, heater matrix - front and rear? - cylinder block).

What about Radflush and stuff like that. I assume as a mimimum (and no doubt my Workshop Manual will tell me so) I should run nthe engine so it is nice and warn and coolant well circulated, then cut engine and promptly drain while sediment may be in suspension

I'm going to change the thermostat (though the old one seems fine, I'd rather do it while doing the coolant change). Will it need any gasket sealant on the housing (for insurance) or - assuming I find one in the replacement part box - will the replacement gasket suffice? If I do need sealant, what would the right one be?

Putting in 50/50 mix. Whats the simple way? Pre-Mix it 50/50 in a watering can then put it in using a funnel? Or find out the capacity of the system and tip in equal parts of water and anti-freeze alternately until it fills?

Thanks chums. I regard this exercise as my most challenging bit of Bongo maintenance yet and am bracing myself accordingly

[neil/di]

I am just about to have mine done and would appreciate something I could print off regarding the flushing of the cooling system
Neil

[mikeonb4c]

Neil - I've got a collection of stuff I put together from past threads and put into a Word doc. Would that help? PM me your email address if so and I'll send it - just saves trawling through BF. I've also sent the doc to Ozric for Bongoogle though whether hte poor bloke has found a moment to put it on there I'm not sure. I still have this mental note though to try and get 'guidance for absolute beginners' on the questions listed above. Sounds like you could use advice too (Peter Humphrey to the rescue?)

Mike

[dandywarhol]

Mike
I would do as you suggest - warm it up, remove the upper and lower radiator hoses and let the old coolant out. Then put the garden hose in the bottom of the radiator or into the hose and flush the radiator backwards - it'll be a bit messy

You could also flush water through the engine block - it might find it's way into the rear matrix - alternatively, remove the rear matice hoses from in below and flush it out that way.

Then replenish with fresh coolant mix and bleed thoroughly as per the manual.

I'd be inclined to leave the thermostat...............all you need is a seized bolt in the alloy to really piss of your day - if it ain't broke....etc.

[mikeonb4c]

Thanks Dandy - invaluable advice. Your mention of seized bolts is spot on. I had forgotten that my garage had had exactly this happen on our old Nissan Sunny. Only they have the tools to dig themselves out of the hole - I dont. I'd bought a new thermostat to put in but can keep it as spare. Is it worth me even trying by putting WD40 on, then using a 12-point ring spanner and sharp (but not excessive) tapping with a hammer to see if it bolts will start moving, or is even that pushing my luck d'ya think?

But with all DIY its always something like that that causes all the trouble (e.g dropping and losing my brake clip in the rai nand wind and spending 2hrs finding it!!)

Thanks again

Mike

[dandywarhol]

Don't even think of a 12 point - you'll only suceed in rounding off the corners..................better to use a 6 point flank drive socket

[mikeonb4c]

I know you are right . I've only got deep 6pt sockets and they dont fit in tight spaces - I'll have to get some shallow ones if the 6pts wont fit. But in principle then, with 6pt and moderate tapping, it might be OK to see if the nuts will loosen without risk of shearing the bolts? It's funny, but despite all the horror stories on tight stabilser bar bracket nuts, mine yielded without any serious trouble - its encouraged me to try again

Seems trivial, this debate, and yet this is what I call the 'real stuff' of working on (older) vehicles. They dont put this in the workshop manuals!

[clogger]

try a bit of heat an all but being ally be careful

[mikeonb4c]

Other thoughts:

If I backflush the block, any danger of crud messing up the thermostat so tha tit plays up after I've refilled the sustem and started using hte Bongo again.

Also, if I do get the thermostat off OK (and I have to admit I may chicken out along the lines advised by Dandy), should I use a gasket sealant (which? I know Dandy mentions Hylomar) when refitting the housing?

Great help all this- I can feel myself bracing to the task (I think!)

Mike

[francophile1947]

Mike
You have to remove the thermostat, and put the cover back on, to properly flush the system, otherwise it blocks the flow of water - just like it stops coolant circulating until the engine is hot.

[Peg leg Pete]

I removed the thermostat with no problems(apart from a little skin removal) perhaps I was lucky. Using Radflush, you should run the bongo for 20 miles, if my failing memory is correct, not an option when our bongo overheated after a mile. I ran a hose through the bottom drain on the radiator and did this several times. I did not need any sealant on thermostat, so not able to comment on that. I filled coolant through expansion bottle and then through bleed pipe, squeezed all hoses to dislodge any trapped air, did not rev at high revs, but that was due to ignorance of not having manual, and wanting my neighbours to still speak to me When the trapped air finally escaped through the bleed pipe it came out at a fair pressure, so be aware good luck Mike, I would be tempted to fit the new thermostat, but of course that is your choice

[mikeonb4c]

Excellent & thanks Peter. Plenty to think about, with Dandys (sensible) cautions. I knew there was a reason I'd have to take the thermostat out to really flush the block, just couldnt make the mental connection that was lurking just below the surface. Old age I fear. Now, where did I put me spanner