Uh-oh - Coolant Woes.

[captain_badger]

Hi all,

It's that time again! Another newbie with an overheating Bongo. I'm currently at about "Stage III" which is "Oh cr@p, I really hope it isn't they cylinder head/gasket".

I had a trouble free motorway run on Friday night. Then yesterday during a quick round town run it decided to go nuclear. I quickly stopped and let it cool before crawling home. Unfortunately it was too dark and I lacked the help of an assistant to give the coolant system a proper look over, but I did attempt the simpler method of bleeding and topping off. I filled the header tank with the radiator cap off until it overflowed. Opened the bleed hose until all the air was pushed out and only water came through and basically repeated the above until everything was full with no air coming out of anywhere. I then bled off a little more so the header tank wasn't over-full.

After running the engine, feeling the heaters blow warm and then applying revs for a good while, the stat never opened and the bottom hose never became warm. Eventually the engine temp rose to 12 O'clock at which point I switched off and noticed a lot of coolant leaking from the overflow of the header tank. Not good. The radiator fans still fire up after a time of letting the engine run - I presume they are controlled by a temp sensor and the ECU rather than the same system as the coolant thermostat? As you can all tell, I'm really learning here. Being a child of the digital age, this is all a bit new to me but I have a decent engineering head on my shoulders so willing to soak up all the wisdom on offer.

Curiously, my heater blowers no longer work - I'm guessing all the water flying around has done that.

So I'm really hoping that I just need to replace the Thermostat, which I have ordered along with a new water pump since I may as well change them both at the same time. I'm planning to order some new hose clips too, and replace as many of those as I can get to. Can anybody please suggest anything else I might want to replace while I have a rare gift of a few days off work next weekend/week?

Cheers!

[mikeonb4c]

Squeezing/identifying a top hose that is not rigid before engine start but becomes rigid v quickly (i.e. before stat can have opened) after cold engine start is i think i've heard a 'kick the tyres' rough pressure test for a system that is being pressurised by a compromised head or head gasket. And there are plenty of things that can compromise effective flow and cooling of coolant. Apart from possible head issues, replacing radiator/thermostat/water pump/engine temp sensor could all be seen as a good investment.

[captain_badger]

Squeezing/identifying a top hose that is not rigid before engine start but becomes rigid v quickly (i.e. before stat can have opened) after cold engine start is i think i've heard a 'kick the tyres' rough pressure test for a system that is being pressurised by a compromised head or head gasket. And there are plenty of things that can compromise effective flow and cooling of coolant. Apart from possible head issues, replacing radiator/thermostat/water pump/engine temp sensor could all be seen as a good investment.

Thanks for the advice, mikeonb4c. Is that a top hose to the radiator, or somewhere else?

Looks like, after quite a lot of reading on here today, that I'll have it up on ramps asap to do a proper coolant bleed and re-fill while I wait for the thermostat to arrive - I think (HOPE!) I have an air lock in the cylinder head after some research. I did notice that the top pipe to the radiator was getting hot very quickly, which at the time I thought was normal but I have since discovered that it is not. I'll know more on Friday when I can have a full day in good light to investigate properly and use the seesaw method. Fingers crossed!

[mikeonb4c]

I think it'll be top hose to radiator. Although not about Bongos, this is a typical discussion:

http://www.peachparts.com/shopforum/die ... -cold.html

[captain_badger]

So after getting some help and doing a proper bleed of the cooling system, I fear the worst for my Bongo. Using the proper method of clearing air from the system, after a very long period, probably the best part of an hour with the front end up on ramps there are still bubbles coming up through the funnel. Curiously only when the engine is idle, no bubbles when revs are applied. The level in the header tank doesn't go down either. Certainly not enough to replace the volume of the bubbles I'm seeing. Coupled with the fact that, as mikeonb4c has suggested, with the cap on the header tank the thick coolant pipe to the top of the radiator gets noticeably firmer after a while. There's a noticeable build up in pressure to the cooling system.

Unless anybody can point me towards any other possible causes and how to check for them, it looks like I'm shopping for a new Cylinder head.

Is this the preferred option for a replacement, does anybody know?

Cheers.

Jack

[mikeonb4c]

Top will get firmer as system gets hot but if its getting firm v soon after start up it suggests combustion cylinder gases causing it. Strange these diesels - mine needed a new head at 20 years of age despite no overheating issues and best care but many have had no issues. I do a lot of short runs and i wonder if this might have aggravated a design weakness through lots of thermal cycling. No matter, that was 3 years ago and all forgotten now, plus engine is quieter as tappets etc all got adjusted as part of the process.

[captain_badger]

Hmmm. Not getting very firm immediately after starting. Only once engine temp gets to normal 11'o clock position. It does concern me that I've had to release a lot of pressure from the system after some runs. But then again if the radiator has leaked (which does seem to be the cause of all this after I've been messing about I have found a lot of excess water along the top of the radiator), the system has taken on a lot of air as a result to replace the water, and air expands more than liquid, there will be excess pressure. I guess at the end of the day I'll never know for sure unless I have it inspected.

I suppose the true test will be to replace the radiator, fix the coolant loss issue and make sure the whole thing is good and then if I continue to have issues, I'll have the head inspected.

[mikeonb4c]

Looking back, my radiator started to leak about a year before the cracked head symptoms caame out. Whether that was related or just age i'll never know!

[cutlass]

for correct check temp - i am install second temp sensor into hotest point of head - into back side cooling canal, near 4- cilinder and connect it "paralel" base temp sensor.....now - "normal temp" - "two o clock"!