Overheating on climbs - V6

[Daydreamer]

I've had a search but couldn't quite find what I was looking for. Live in mid Wales so lots of climbs, the Bongo has always handled them well with no issues. It's a V6 with LPG and side conversion, I have a coolant alarm fitted but no temp alarm as yet. Anyway just before Christmas while driving home up a climb the temp gauge shot up 3/4 of the way so pulled over before it got any worse and coolant overflowed from the expansion vessel. Let things cool down topped up and got home fine, checked for leaks, fan working, cap holding pressure, etc with no issues

Few days later drove it to my nearest Bongo garage (40 miles) with no issues, garage did leak tests / compression tests / checked thermostat / rad / leaks / coolant cap / water pump etc ..... no issues found and everything worked well, they couldn't find anything wrong. On the way back tonight, Bongo drove really well on all roads but temp rose again while climbing that same section, on the flat spots temp dropped but then would rise again on the climbs.

Got home fine without loosing any coolant and not overheating. Not sure what could be causing the issues.....any ideas guys?

[the laird]

If the rad ain't blocked and all else is ok and you've no coolant. Loss could it be the temp transmitter at fault?
You say the stat n all has been checked,might be worth a try.take it that the coolant is not building up pressure

[Bob]

If the stats been checked was it bled properly?

My brother has just bought a V6 (from a motorhome dealer, not a Bongo garage) and when I mentioned the need to bleed he has been told, "No need to bother on the new ones, Mate, its all sorted out".

[francophile1947]

Is your gauge unmodified, in which case it doesn't go passed 11 o'clock until the engine has overheated, or has it been modified so that it actually moves when the coolant gets warmer?

[BongoBongo123]

Cannot add much but maybe have a look around the turbo If a petrol has a turbo, sorry not sure it does ?) as that is water cooled and I had a leak there luckily without any major damage being done. When mine went water was dripping from underneath around the front of the side door kind of area.

Incidentally if anywhere would cause some heat issues it could be Wales my temp alarm went off up a 500ft Brecon hill/mountain when we was in your beautiful country just for a single night. I saw a cement mixer on the same part of the road with smoke belching out of the axle ! It is hard going on those hills of yours. Hope you get to the bottom of it.

Just an annoying thought... can the cylinder head crack between the outside of it and a water way ? This may not show up as losing compression if there is no crack between the cylinder and the outside world so to speak. Not what you want to hear but I think 3/4 way up might be very hot. Maybe go round the block and look every where to see if there is any water (though it might evaporate quickly if the block is very hot) Maybe check all is dry and doa short run and check the cylinder head for any water before the engine has warmed up. Just a thought from a not too technical person here.

Good luck.

[Daydreamer]

Hi - many thanks for the replies and advice

If the rad ain't blocked and all else is ok and you've no coolant. Loss could it be the temp transmitter at fault?
You say the stat n all has been checked,might be worth a try.take it that the coolant is not building up pressure

Haven't checked the temp transmitter, but will do; as far as I know coolant is not building up pressure

If the stats been checked was it bled properly?

My brother has just bought a V6 (from a motorhome dealer, not a Bongo garage) and when I mentioned the need to bleed he has been told, "No need to bother on the new ones, Mate, its all sorted out".

.

The garage I use was initially found on the members club sheet and as fas as I know they know what they're doing, they last serviced it and I've done about 6000 - 7000 miles with no issues.

Is your gauge unmodified, in which case it doesn't go passed 11 o'clock until the engine has overheated, or has it been modified so that it actually moves when the coolant gets warmer?

I'm not sure if the gauge has been modified or not. Temp climbs to just under half way and normally just sits there, tonight I noticed it moving past the half way point and back down. As the engine worked harder temp rose but also dropped rapidly as soon as the road flattened out. The only time it got 3/4 of the way up I pulled over and that's when the coolant overflowed.

Could the thermostat be sticky in some way, I'm at a loss what might be causing this.

[Northern Bongolow]

try changing the rad they get partially blocked, and 18-840c in the drawing below, this controls when the fans come on to cool the system when working hard.
is it using any coolant ??

http://lushprojects.com/bongopartsmk2/c ... o=.html#11

[Daydreamer]

Thanks BongoBongo 123 - you must have posted just as I was replying to the others. I'm pretty sure the head is OK but will have another look tomorrow. We're really up in the wilds here too, love it

try changing the rad they get partially blocked, and 18-840c in the drawing below, this controls when the fans come on to cool the system when working hard.
is it using any coolant ??

http://lushprojects.com/bongopartsmk2/c ... o=.html#11

That's great advice too, no loss of coolant though. I'll pass the schematic to the garage and get the sensor ordered in.

Thanks guys for the great help all round.

[the1andonly]

Long shot
Do you frequent the road between Welshpool and Dolgellau ?
I Have a modified temp gauge and since first encounter with this road have added an additional gauge and modified the scavenger fan to come on with a dashboard switch.
No problems anywhere else in England or Wales.
Only on this road when towing ie real load have I had frightening gauge experiances but no coolant problems.
A slightly less than perfect system may be tested by this road.
In addition Ive travelled this road towing same trailer with an Audi A4 with nowt alarming (but then again never looked at gauge in same way as I do with the Bongo).

also noticed temp soon comes down ie no load and cooling on way down the hill, stopping would allow no cooling and possible increase in temp and pressure.

[Simon Jones]

My brother has just bought a V6 (from a motorhome dealer, not a Bongo garage) and when I mentioned the need to bleed he has been told, "No need to bother on the new ones, Mate, its all sorted out".

Oh how so very wrong. V6 needs bleeding in the same way as the diesel. The 2 litre however is self bleeding

[Daydreamer]

Long shot
Do you frequent the road between Welshpool and Dolgellau ?
I Have a modified temp gauge and since first encounter with this road have added an additional gauge and modified the scavenger fan to come on with a dashboard switch.
No problems anywhere else in England or Wales.
Only on this road when towing ie real load have I had frightening gauge experiances but no coolant problems.
A slightly less than perfect system may be tested by this road.
In addition Ive travelled this road towing same trailer with an Audi A4 with nowt alarming (but then again never looked at gauge in same way as I do with the Bongo).

I like the idea about the modified scavenger pump - good work. We're up in the hills south of Machynlleth......need to get to the bottom of this problem soon as I can't avoid the hills here.

[Simon Jones]

I read in one part of the thread that coolant came out the expansion tank but it was also mentioned no coolant was lost. One of these cannot be correct. Sounds to me like either the water pump is not doing its job, there is a blockage somewhere or there is an airlock in the system. Get an external temp sensor connected to one of the heads and you will be able to get a better idea of what is happening. On my V6 I think the hottest its got is about 96C on the climb to Applecross (Bealach na Ba), which if you know it, is basically like driving up the side of a mountain.

[Daydreamer]

I read in one part of the thread that coolant came out the expansion tank but it was also mentioned no coolant was lost. One of these cannot be correct. Sounds to me like either the water pump is not doing its job, there is a blockage somewhere or there is an airlock in the system. Get an external temp sensor connected to one of the heads and you will be able to get a better idea of what is happening. On my V6 I think the hottest its got is about 96C on the climb to Applecross (Bealach na Ba), which if you know it, is basically like driving up the side of a mountain.

Hi Simon, sorry it should have read no coolant loss second time around as I was coming home last night. First time there was a loss of coolant....sorry had a long day yesterday . If there was an airlock would it show itself in 'normal' driving conditions? This overheating seems to only occur when the engine is working hard getting up a longish climb, but I never push it hard on the speed and keep the revs low. I'll get a temp sensor and see what that says.

[Simon Jones]

Thanks for the update. Coolant coming out of the overflow can be caused by three things.

1. The cap has a spring loaded rubber disk that forms a seal on the neck of the expansion tank. Sometimes the rubber disk or the mating surface of the tank can become damaged or the spring weakens which can allow coolant to escape at less than the 1.1 bar pressure that it is designed to let go at. A visual inspection and / or replacement cap or tank would eliminate this.

2. If the coolant is not being cooled properly by a partially blocked radiator, a stuck/lazy thermostat, fans not running when they should or ineffective pump then the coolant will start to boil which increases the pressure in the system. Draining the coolant, flushing the system out with lots of clean water and refilling with correct strength good quality anti-freeze would be a good inexpensive starting point.

3. Excess pressure is being put into the cooling system. On a previous diesel Bongo, I had the head gasket fail which meant the combustion gases from the cylinders was escaping into the water cooled jacket that surrounds the head. The V6 engine is not known to suffer from this happening and I can only recall of one person on the forum who has experienced this. As the gas gets into the system it can cause an airlock such that the coolant does not circulate properly which then causes the engine to get hotter which increases the pressure in the system and coolant is forced out the expansion tank.

Even without any head gasket issues, if air gets into the system it can cause an airlock which can result in localised heating and then the temperature / pressure builds up. A damaged bleed hose for example can sometimes allow air to be drawn into the system as it cools down. Air expands faster than water so as the pressure builds up it forces coolant out the system which then perpetuates the overheating cycle.

When I bought my V6, I took it for a drive and it all seemed fine. Once I'd handed over the money, I was having a blast down the dual carriageway and I noticed the temp gauge went up higher than expected and then dropped as I slowed down. This was slightly unnerving as Bongo temp gauges are highly damped so you rarely see any movement once at operating temperature. First thing I did when I got home was drain, flush, refill and bleed the system and that solved the problem. I've since modified the gauge such that it more accurately reflects what is happening. Now it runs around the 12 o'clock position most of the time, but can rise to the 2 position after a steep climb when you get to top and you stop so there is no airflow to take the heat away.

My suggestion would be to check the coolant level this morning as it may have dropped a little when cold and then keep a close eye on things. A low coolant alarm is a great help. Check the cap while you're there and if the problem persists, change the thermostat with genuine Mazda part (about £44) and drain, flush, replace coolant. Bleeding system afterwards is vital to get all the air out. New radiator might be a wise investment too. Pattern parts start from about £60 to £100 while genuine Mazda rads are £250.

[rita]

"temp gauge shot up 3/4 of the way " doesn't really mean much with a doctored gauge unless you know what the actual temperature the cooling system is running at.