Overheating. What's gone wrong with my bleeding technique?

patmckenna · Post by **patmckenna** » Sun Apr 01, 2007 10:59 pm

Hi Guys,
I had an overheating problem a few weeks back which was caused by a leaking hose. With the help of Peter Humphery, we managed to solve the difficulty of bleeding the system. This lasted for three weeks or so - including the Dent trip which combined motorway and country lane driving.

The problem reoccured on Friday afternoon - the reservoir boiled over, temp shot up, etc. I bled the system without success so I decided to fit a new thermostat in case there was an on-going problem with this unit. I managed to complete this fiddly little job this morning...

Here's where I need some advice. I went through the bleeding routine very carefully but keep coming back to the following scenario. Instead of air gently bubbling through the bleedhose (connected to a funnel filled with anti-freeze etc) we get great gurgling/gushing of water. When it begins this episode, we lose the water from the reservoir. If I rebung the bleedhose, it rapidly builds up pressure and can then be released as steam. Somewhere in my head, I hear the expression 'back pressure' but don't really know what it means.

I suspect I have a problem beyond inadequate or incompetent bleeding. The radiator seemed to be okay - I flushed it out, back-flushed it etc. and it flowed through freely. Is the next step to have the whole system pressure-tested? Have I blown a head gasket or worse?

Should I take a calming pill while I wait for some answers?
Pat

Harry · Post by **Harry** » Sun Apr 01, 2007 11:17 pm

Pat..why do you bung up the bleed pipe?

Warm up engine but not so its hot

Just keep filling up the reservior ..run the engine with the bleed pipe open...when reservior gets low..turn engine off...top up reservoir...turn engine on..repeat until you get no bubbles from bleed pipe. Turn engine off.. seal bleed pipe.

It worked for me!

cheers

H

mikeonb4c · Post by **mikeonb4c** » Sun Apr 01, 2007 11:29 pm

Pat - are you following the procedure in the workshop manual to the letter. Do you have someone with you to top up the reservoir while you are watching the bleed tube. I must admit I found bleeding the system on my own a bit harrowing, but by luck more than judgement I think, I got away with it. I'd want to be absolutely sure I'd bled the sytem following the workshop manual to the letter, before I started pulling things to pieces. Apologies if you've already done this.

Good luck

Mike

Harry · Post by **Harry** » Sun Apr 01, 2007 11:33 pm

Should point out that it is normal to get gouts of water mixed with air and lots of bubbles/hot air/steam/etct coming out of the bleed pipe until the system is full.

As mike says..its easier if there is someone else pouring coolant/water into the reservoir at the same time.

good luck

H

patmckenna · Post by **patmckenna** » Mon Apr 02, 2007 12:58 am

Hi Guys,
Thanks for the replies. Words get in the way of explanations at times. I need to clarify that I went through the bleed process with two of us working the system - one filling from the reservoir, the other at the bleedhose end keeping things working. We got to a point when we no longer had any air so I took it for a test run. Within minutes, the temp shot up and the reservoir overflowed under great pressure.

Subsequent attempts at bleeding, following the same methodical procedure, resulted in the strange phenomenon of the water gurgling and spitting quite rhythmically, in tune with the engine beat, with the temperature increasing dramatically all the time. Eventually I had to rebung to avoid a scalding.

I agree that I should expect lots of air/steam/bubbles etc and when that happened on occasions I was pleased because the process was obviously working. What I am trying to describe appears to me to be a stage beyond the business of bleeding out the air. I would like it to be a self-perpetuating error in my bleed procedure, but it just feels like something worse - the build-up to superhot when the system was open and being filled and bled seemed to me to be mimicking the overheating being experienced in the pressured system.

Harry and Mikeonb4c - thanks for the input. I mentioned the rebunging almost as an aside. When the coolant became very hot, we bunged it for a while to let things calm down. When I opened it up again, the steam produced was prolonged and (I think) excessive.

I'm knackered and deflated, so I'm off to bed. No doubt optimism will return by morning.

Thanks for the help and encouragement.

Pat

Taxiback · Post by **Taxiback** » Mon Apr 02, 2007 10:51 am

Sorry to say it but it sounds like your head gasket.
I find bleeding a bongo pretty straight forward, if you are on your own try placing a piece of mdf or plywood over the gap under the drivers seat cut to fit so you can rest your bucket there without it having to balance on the edge.
Get the bleed hose and place it through the bottom of the steering wheel and use the zip tie that normally holds it in place under the passengers seat to hold it onto the steering wheel.
Now with the hose pointing down into the bucket turn on the engine then go round to your expansion tank and remove the cap and top up the water.
To bleed a bongo properly and remove all the air you need to have it rev at 2500rpm for 6 mins to achieve this I use a piece of wood again cut to the right length and wedge the throttle down.
while it is revving you can stand at the expansion tank and keep the water level topped up.
On my bongo with a new radiator/thermostat and head I found that once bled I have a steady flow of water out of the hose on tickover.
Hope you find this of some help.

patmckenna · Post by **patmckenna** » Mon Apr 02, 2007 12:01 pm

Hi Guys,
It's daytime again, I'm at work and awake and ready to face the overheating Bongo again. Thanks Taxiback for your post, very precise details and extremely helpful.

I'll have another go in the next couple of days and see where that takes me.

Thanks for the help. Sometimes it's great to spread your misery a little wider than foul language underneath a wet, gurgling Bongo...
Pat

mikeonb4c · Post by **mikeonb4c** » Mon Apr 02, 2007 1:01 pm

Pat

I did all that Taxiback suggests when I did mine. I would still prefer to be able to relax and observe the bleed pipe close up, confident that someone else will top up the header tank as needs be. I remember I had underestimated the amount of 50/50 I needed to have premixed, so had to include that in my running around the Bongo. It wasnt fun, and I felt that if I had once been late and the level got too low, it would have undermined all my work. So relax, get a friend to help if you can.

Next question. You don't say whether you EXACTLY followed the workshop manual routine. I dont have it withe me at work, but it goes something like this:

Warm engine up
Run at 2500rpm for 7 mins
Run at tickover for 3 mins
Run at 2500rpm for 7 mins
Run at tickover for 3 mins
Run at 2500rpm for 7 mins
Run at tickover for 3 mins
Run at 2500rpm for 7 mins

Let engine cool then finally remove header tank cap and give it a final top up.

Throughout, there are reminders to check the bottom hose gets hot (interesting in view of the current BF poll), and that the temp gauge does not get hot. If either of these causes problems, you are to let the car cool andstart again.

It is more precise than that (and a little vague on when you should put the header tank cap on - I think I put mine back on at first then thought I shouldnt have - it must make some sort of difference if the system is pressurised or not - as I say I got away with, or appear to have). But I think you need to be sure you have done EXACTLY what the manual says.

Next, lots of stuff on BF about how easy it is to check water / get water checked for oil in in etc. etc. in order to confirm there is a head problem.

Last bit. You said:

strange phenomenon of the water gurgling and spitting quite rhythmically, in tune with the engine beat,

Not being able to sit watching my bleed pipe, I cant say if this happened in my case. But the 'in tune with the enginer bit makes it sound as though something like a head problem could be occurring, though I'm no expert. Where else might the rythm come from?

Cant think of owt else. Good luck & keep us posted.

Mike

patmckenna · Post by **patmckenna** » Mon Apr 02, 2007 1:36 pm

Hi mikeonb4c

Thanks for the detailed post. You stumbled on one of the difficulties I faced in trying to interpret the sequencing - i.e. when do I put the reservoir cap on?... 'Taxiback' infers that he keeps the reservoir cap off until the process is complete. I've got the manual - so I'll look at it more closely.
Thanks again for the input. I'll keep you informed.

Pat

Dannyboy · Post by **Dannyboy** » Mon Apr 02, 2007 1:57 pm

Hi Pat,

Sorry to hear of your troubles. I have had pretty much the same problem for a while now. You can read about it on another thread "Overheating Again!!". I have now bled my system on numerous occasions in the last month and I expect you are doing it fine. I think it likely that the reason it is not working is that you have some other problem.

As far as I can see the point of all the 2500 revs for three minutes etc is to purge the air from the system and to allow the thermostat to open to allow water in and air out of the main cooling circuit which returns from the radiator to the thermostat

You can check the heater circuits by feeling the hose leading from the thermostat to the side of the vehicle under the passenger seat, If the metal pipe that this leads to is hot on both sides and the heaters are blowing hot, the water should be circulating. I usually try to help the coolant around by blowing into the radiator at the cap and by blowing back into the bleed hose.

You check the main cooling circuit by feeling the lower radiator hose at the radiator. If it is cold. this, as far as I can work out, means the thermostat has not opened. When it is warm or hot the stat should be open.

I am finally coming round to the view that it is my radiator that has caused all the problems. It is over ten years old which is pretty good for a rad.

I removed it yesterday and flow tested it. Put a hand over lower pipe, filled radiator, removed my hand. Water shot out about 9 inches. Seemed not too bad. Laid it flat and filled it with hot/boiling water. Could clearly feel cool areas, mainly lower down and on the left side when looking at it from the front of the vehicle.

It is certainly partially if not completely blocked. It is ten years old so decided to change it. New one ordered from Dave at Vospers in Exeter. £126 + VAT, less 7% as a Bongo Fury member, + £8.50 postage. The best price I could find.

Hopefully it will arrive tomorrow or Wednesday. I am on holiday this week and will fit it as soon as it arrives, hoping it resolves my long standing problem. If you can wait for a few days to see if it works it may save you the cost of a tow to your bongo friendly garage.

It is not too difficult to remove the rad. I did it with the vehicle on the ground. If I were to do it again I would put it on ramps.

Drain system.
Remove air inlet gubbins above radiator.
Remove top and bottom hoses and feed hose from the header tank.
Remove black plastic air inlet for intercooler(?) below radiator.
Remove two feed pipes from the gearbox and plug them. I used 10mm drill bits and clamped them with the hose clamps already there.
Undo two or three electrical connections and move cables out of the way. Undo two bolts at the top of radiator.
Carefully lift radiator up and out for testing.

Not too difficult and shouldn't take too long if you are reasonably handy.

I'll let you know how I get on. I am reasonably hopeful this will will work. If it doesn't I'll be seriously scunnered.

Happy bongoing.......when you get it mobile again.

mikeonb4c · Post by **mikeonb4c** » Mon Apr 02, 2007 5:05 pm

Dannyboy - how did you find it getting the hoses off. They can be pretty tight once bedded in. Interested to know & thanks.

Good luck with the new Rad. - I'll keep my fingers crossed for you. On way to look at it is that it needed doing anyway etc.

Mike

Dannyboy · Post by **Dannyboy** » Mon Apr 02, 2007 5:55 pm

You're right Mike,

the new one should last another ten years. I didn't have much trouble getting the hoses off. I moved the spring clips with a pair of pliers, then using a small screwdriver eased it underneath the hose where possible, to break the seal between the hose and its pipe, then while pulling and twisting the pipe, eased/forced the hose off with a large screwdriver. A little bit of care and a great deal of brute force is often the answer.

Harry · Post by **Harry** » Mon Apr 02, 2007 7:50 pm

For a detailed description of how to change the radiator visit the members section...my one claim to technical fame last year!

mikeonb4c · Post by **mikeonb4c** » Tue Apr 03, 2007 12:11 am

My technique exactly Dannyboy. You know, when you re-read your posting it is ah....um.....er.......

.......easy to imagine you are talking about something else altogether. Ah happy memories

antique · Post by **antique** » Tue Apr 03, 2007 7:28 am

hi i think you will find you have cracked head ,try and get a dye test to confirm?