Back Pressure

David Edwards · Post by **David Edwards** » Sat Nov 26, 2011 1:01 pm

Just back from a great couple of days in london and went to see my poorly bongo, Problem with back pressure..starts and runs and sounds great but there is constant back pressure into the header tank from the larger hose, now the garage said they have bled her as per the three superb videos on youtube with, Kirsty, haydn and Ian, all pipes get hot as supposed to bu this constant pressure which is emptying the header the tank cannot seem to be resolved, so..any ideas guys, are they just not bleeding long enough or does it point to something else, thay said all pipes are fine as are clips etc.

dandywarhol · Post by **dandywarhol** » Sat Nov 26, 2011 1:46 pm

Back pressure sounds like it's getting cylinder pressure into the cooling system David.

I haven't followed all what's being going on with your van but I gather it's had major surgery.................

IF it's been bled properly, and it sounds like it has, if it's getting cylinder pressure then the best diagnosis is to have a dye test of a sniffer test to determine if there's any combustion gases present in the cooling system - any MOT station could use their 4 gas analyser to "sniff" for carbon dioxide.

gasace · Post by **gasace** » Sat Nov 26, 2011 2:58 pm

dandywarhol wrote:Back pressure sounds like it's getting cylinder pressure into the cooling system David.

I haven't followed all what's being going on with your van but I gather it's had major surgery.................

IF it's been bled properly, and it sounds like it has, if it's getting cylinder pressure then the best diagnosis is to have a dye test of a sniffer test to determine if there's any combustion gases present in the cooling system - any MOT station could use their 4 gas analyser to "sniff" for carbon dioxide.

I have a flue gas analyser that can read carbon dioxide should the probe go into the top of the expansion tank wit the engine running? or do I need to take a sample of water in a jar and shake it to release the CO2?

teenmal · Post by **teenmal** » Sat Nov 26, 2011 3:13 pm

Hi David,

Its a bit of a long shot but does, or can your mechanic do a Vacuum refill.

Cheers.

dandywarhol · Post by **dandywarhol** » Sat Nov 26, 2011 4:50 pm

gasace wrote:
dandywarhol wrote:Back pressure sounds like it's getting cylinder pressure into the cooling system David.

I haven't followed all what's being going on with your van but I gather it's had major surgery.................

IF it's been bled properly, and it sounds like it has, if it's getting cylinder pressure then the best diagnosis is to have a dye test of a sniffer test to determine if there's any combustion gases present in the cooling system - any MOT station could use their 4 gas analyser to "sniff" for carbon dioxide.

I have a flue gas analyser that can read carbon dioxide should the probe go into the top of the expansion tank wit the engine running? or do I need to take a sample of water in a jar and shake it to release the CO2?

It should be sufficient to let the flue analyser "sniff" for CO2 from the expansion chamber with the engine running

haydn callow · Post by **haydn callow** » Sat Nov 26, 2011 9:21 pm

You won't want to hear this, but my guess is a "blown" head.

David Edwards · Post by **David Edwards** » Sat Nov 26, 2011 9:57 pm

thanks guys, hope not Haydn it's a brand new blooming head.

dandywarhol · Post by **dandywarhol** » Sun Nov 27, 2011 11:40 am

But it sounds like its not sealing to the engine block properly and causing excessive pressure. Get the garage to attach a pressure tester to the expansion tank and start the engine, if pressure immediately builds up then theres a sealing problem. Couple that with sniff test and you'll have your (unwanted) answer.

gasace · Post by **gasace** » Sun Nov 27, 2011 3:27 pm

dandywarhol wrote:
gasace wrote:
dandywarhol wrote:Back pressure sounds like it's getting cylinder pressure into the cooling system David.

I haven't followed all what's being going on with your van but I gather it's had major surgery.................

IF it's been bled properly, and it sounds like it has, if it's getting cylinder pressure then the best diagnosis is to have a dye test of a sniffer test to determine if there's any combustion gases present in the cooling system - any MOT station could use their 4 gas analyser to "sniff" for carbon dioxide.

I have a flue gas analyser that can read carbon dioxide should the probe go into the top of the expansion tank wit the engine running? or do I need to take a sample of water in a jar and shake it to release the CO2?
It should be sufficient to let the flue analyser "sniff" for CO2 from the expansion chamber with the engine running

Thank you

David Edwards · Post by **David Edwards** » Sat Dec 03, 2011 2:08 pm

Hmm peeps they dismantled the engine again and a piece of metal has broken off the top of one of the pistons, never seen this before, so I need a piston, anyome any ideas where I can get one please, hopefully this will be it then, got to get a new gasket as well,lol.

helen&tony · Post by **helen&tony** » Sat Dec 03, 2011 2:15 pm

Hi David...
I don't want to be pernickety over it, but have they determined the cause???...I don't think I'd accept them doing the job without knowing WHY it happened...also...am I mistaken, or did you say it's in London?...is there not someone more local?.....
Good luck...
Cheers
Helen

David Edwards · Post by **David Edwards** » Sat Dec 03, 2011 4:26 pm

Hi Helen no its my local garage, they are looking into it for me, so will wait and see what happens, if it needs a new engine, don't know what I will do,lol.

dandywarhol · Post by **dandywarhol** » Sat Dec 03, 2011 6:46 pm

This sounds pretty drastic David - pistons don't break easily so there must've been a bit of butchery done at some time for that to happen. It's imperative the reason for the broken piston is found! I recall reading that the "garage" had problems timing the engine, on a diesel a tooth out can cause piston/valve contact - was the head skimmed??

The fragment of broken piston probably caused the head gasket to rupture and the effect is pressurising the cooling system. any chance of a photo of the damage?

PS - when you end in lol.......are you signing off as "lots of love" or "laughs out loud"?....................just curious

Northern Bongolow · Post by **Northern Bongolow** » Sat Dec 03, 2011 7:03 pm

i can find you a second hand parts supply david, my mate is breaking a diesel and v6 engine. and i think simon jones has an old engine he is prepared to break or is breaking.
but like the others i would want to know why and what else is damaged if anything before chuck more into this.
check the valves/stems/ rockers on the coresponding cylinder for damage.and if the piston is hit is the conrod/crank ok.

David Edwards · Post by **David Edwards** » Sat Dec 03, 2011 8:59 pm

thanks folks, I have told them I want a thorough investigation as to the cause, it is actually a bit of the rim that has broken away, I have looked at the new head I gave them and valves, they look fine, will find out more in the week. Just want this year over with now, not been the best for me, took the dogs out this afternoon, got back to the car and missus said, Oh dear cant find the keys, bloody lost em in the country park, what a shite day, traced our steps, nothing, so expense again now for spare key and alarm fob etc for the rover, electrics failed in the house yesterday, took the leccie hours to find the problem.

Back Pressure

Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure

Re: Back Pressure