Overheating & coolant levels

[MikeHighlands]

Hi,

Please forgive me if this is the kind of post typical of Bongo owners who don’t know their engines and if some of you are rolling your eyes and thinking “inevitable” when reading! I have a 1996, 2.5 turbo diesel, 2 wheel drive, with 108 000 miles on the clock. I’ve had it about 15 months, I’ve done about 20 000 miles in it and I knew nothing about engines or car maintenance when I purchased. However, I now want to learn what is necessary to keep my van in the best possible condition for as long as possible. I have, for example, been taking care to treat the rust on the wheel arches.

Anyway, the other day I drove a few miles, picked up my son, re-started the engine and it cut out as if it had stalled. I was shocked as it has never done this before. I re-started and after about fifty yards I could see the temperature gauge rising. I pulled over as soon as it was safe to do so (a few hundred yards down the road). I lifted up the bonnet and coolant was spurting out of the header tank. After waiting for the engine to fully cool down I tried to drive it the 3-4 miles to home. It overheated again, after going uphill, so I stopped and waited (this time I had the sense to top up the header tank when it was cooled down) and then I got home with no overheating. I spoke to my mechanic on the phone (he is 34 miles away) and quickly renewed my RAC membership which had just expired. As the coolant level in the header tank now didn’t appear to be dropping, and there was no sign of any ‘white deposits’ in my oil and because my heater was working fine he suggested I drive it another few miles to see if it overheated again (he wanted me to drive to a place in town where they would test the header tank for emissions so we could ascertain if the cylinder heads had gone). It overheated again! After waiting ages I got it home without it overheating and the next day I called out the RAC.

The guy from the RAC tested for emissions in the header tank, there was no reading. He couldn’t see anything wrong with the radiator or any leak in the cooling system. I showed him the pipe leading into the head gasket (that I check after reading this article - http://www.practicalmotorhome.com/advic ... yers-guide) which was all fine, and there was still no sign of anything wrong with oil. We bled the coolant system (him assuming there was airlock in the system) and then turned the engine over, no overheating, we upped the revs, no overheating, I drove a couple of miles, no overheating. After three hours he left, happy that the van was at least OK for me to drive to the garage. I am booked into the garage on Monday (I need an oil change, a seat fitting and the underneath being re-sealed as well). I have driven the van twenty miles since. The engine is sitting at its normal temperature (just below half way on the gauge), the coolant level is not falling and the oil is showing no sign of any deposits or anything odd and the heaters are working fine. I suspect that when I go to the garage the mechanic will perhaps not be able to diagnose what the problem was, as the man from the RAC was also slightly perplexed. Also when I first bought the vehicle last year, it overheated once shortly after purchase – I topped up the header tank and it never happened again. I took it to the mechanic who checked it over, but was ultimately unsure of why it had happened, other than there was probably some air trapped in the cooling system. He was confident the cylinder heads had not gone after checking for emissions in the header tank. I checked the coolant level regularly, but it never again had dropped when I checked it. At the time of the overheating this week, I must admit I had grown complacent, and had not checked the coolant level in about four weeks.

The man from the RAC wondered if the cylinder heads had gone (causing a slow leak in the cooling system), but had gone in a place where it wouldn’t be causing emissions into the header tank or for it to show in the oil. He was just guessing though. He did say it would cost a lot to open them up and examine.

I see from reading these forums that a lot of people recommend fitting a coolant level alarm. I can see now that this is sound advice, but it does raise the question – Why would the coolant level drop other than the cylinder heads having gone? Why is it stable for a long time and then drops? If I fit an alarm and the level drops, do I just top up and watch, or do I take it straight to a garage? Should I learn how to bleed the coolant system (I watched the Youtube clips and at first I thought it looked too complex for me, but after doing it with the RAC man I realised it wasn’t too difficult) and do it every now and again? Should I ask the mechanic to take off the cylinder heads and check them even if we are still getting no emissions in the header tank?

Apologies for the overly long post by the way. Thanks for reading and cheers for any advice,
Michael.

[BongoBongo123]

If fluid level drops it means it is either coming out of a tiny hole in a pipe (rubber hose or pinhole in a metal rear heater pipe), a pipe that is not well clipped or steaming out of somewhere or through a tiny crack in the cylinder head. It is easy /optimistic to think "oh it is normal for it to lose a bit" but this is supposed to be a pressurized/normally sealed system (unless pressures become too high for some fault reason). And coolant loss tends to suggest a problem in the making if not checked out.

The coolant alarms and/or temp sensing alarm are essential on these vehicles as they inform of impending issues hopefully before serious damage is caused.

The un modified temp gauge on the Bongo dash is next to useless, by the time that is showing a problem and yourself seeing it is not usually a good situation for the engine.

What I can say through recent experience is a test on the coolant system for exhaust gasses is an indication and not a guarantee. After a new rad, thermostat and fan switch mine seemingly was working ok until it hit a specific temp during actual driving and then it blew out the expansion tank and pumped the hoses up with exhaust after certain driving conditions were met. Sadly my head was cracked and has just been replaced.

With luck this overheating you just have a tiny leak which results in loss off coolant and an overheat when it drops below a certain level. Hard to be sure but I know I would fit both alarms and keep a very close eye on it all and get it checked by someone who really knows what to look for and test for. Be vigilant and very careful.

To be sure the ideal would be a full cooling system check by someone who knows these vehicle's cooling system inside out. For no fault of my own (trying to prevent overheating I had coolant changed by an incompetent/lazy garage or as I personally suspect a bad decision delegating a task to a inexperienced junior) I ended up with a very big bill. There is a very fine balance between leaving well alone, keeping a good check on things and preventative maintenance.

It is a bit of a jungle overall with the cooling system.

[g8dhe]

The pipes are all getting rather old and quite often develop pin holes, which squirt out coolant when under pressure which then evaporates leaving little trace and then as it cools down sucks air in, do this for a few cycles and there is sufficient air in the system to cause an airlock and then an overheat. Once this happens and you fill up all seems fine again for a while until the air builds up again. Also slow leaks from the water pump are much the same.

[teenmal]

This is the symptoms that you can get with a Sticking Thermostat, the thermostat operation is vital ,if it is sticking in the closed position the engine Will overheat and blow out coolant. Worth checking or just replace it if it is intermittent.

[MikeHighlands]

Thanks for the replies! I'll collate all the advice I get and run through all the possibilities I am then aware of with the mechanic. Unfortunately, I don't know of anyone in Inverness with huge experience of bongos. I go to the mechanic I do, because he had the most experience with them that I could find. He seems to look after a few in the Highlands. I would appreciate some advice with what coolant alarm & temp sensing alarm to buy and if there is anything I should discuss with the mechanic with regards to the fitting of them.

Thanks, as always.

[BongoBongo123]

The popular ones used by people here are sold by Haydn alarms. There is a TM-2 temp sensing alarm which connects to the rear of the cylinder head using a bolt and a standard low coolant alarm (LCA)

http://www.coolantalarm.co.uk/shop/inde ... at&catId=8

There are others for cheaper but I use the TM-2 here and it works well. Given the costs involved of failure saving money seems a bit short sighted.

[Northern Bongolow]

ask your mechanic to do a pressure test on the cooling system, this should ensure that the system is pressure tight. this is done by fitting a bike pump to the pipe that is on the expansion tank(the thin black open ended one). fit your pump via a home made adapter to the open end and inflate the system when cold to no more than 1 bar, this allows you to take your time and look round for external pipework leaks. it will not always show up leaks that leak when the bongo is cooling down or some leaks on the water pump but will get most.

click the link below and look where the water pump leaks usually when at rest not running and hot, this is because the water pump seals can seal with the internal heat or pressure that is present when running, but can leak when the system cools as the internal pressure drops to zero. this leak on the water pump is very hard to see as there is a pulley hiding the tell tale hole at the 6 oclock position, not to be confused with the tell tale hole at the alternator side of the pump roughly at the 2 oclock position when viewing from the front of the bongo.

http://igmaynard.co.uk/bongo/forum/view ... ak#p572203