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[DaveyDavey]

Several days ago after a particularly violent downpour of rain I pulled in to get some fuel and noticed some steam coming out of the bonnet. This dissappeared after a minute or two and I wondered whether it was anything to worry about. As nothing further occured I put it to the back of my mind.

This morning though on the way in to work I noticed the  temperature gauge had crept up to just under the red and then carried on to illuminate the warning light. I duly pulled over and checked under the bonnet, couldn't see anything major and there was definitely fan noise.

I got back in the car and turned the ignition on and the temp had dropped a few degrees. Which I thought odd, as the total time elapsed was about 2 minutes and the warning light had gone off.

I carried on my way and noticed the needle creeping up again and as soon as the warning light came on I pulled over to the side and turned the engine off. Then put the ignition back on. Sure enough the temperature started to creep down again.

Having checked on here over the course of the day I am wondering whether it could be one of two things:

A) Fuse gone that controls one of the fans and therefore cooling power has been lost.
B) HBV has gone - which is why there was a little bit of steam coming out the other day.

First thing I will be checking is the fuse and all the coolant/water levels. Other than that, is there any way to tell whether the HBV has gone with a simple test?

Thanks in advance  

[FRE07962128]

Several days ago after a particularly violent downpour of rain I pulled in to get some fuel and noticed some steam coming out of the bonnet. This dissappeared after a minute or two and I wondered whether it was anything to worry about. As nothing further occured I put it to the back of my mind.

This morning though on the way in to work I noticed the  temperature gauge had crept up to just under the red and then carried on to illuminate the warning light. I duly pulled over and checked under the bonnet, couldn't see anything major and there was definitely fan noise.

I got back in the car and turned the ignition on and the temp had dropped a few degrees. Which I thought odd, as the total time elapsed was about 2 minutes and the warning light had gone off.

I carried on my way and noticed the needle creeping up again and as soon as the warning light came on I pulled over to the side and turned the engine off. Then put the ignition back on. Sure enough the temperature started to creep down again.

Having checked on here over the course of the day I am wondering whether it could be one of two things:

A) Fuse gone that controls one of the fans and therefore cooling power has been lost.
B) HBV has gone - which is why there was a little bit of steam coming out the other day.

First thing I will be checking is the fuse and all the coolant/water levels. Other than that, is there any way to tell whether the HBV has gone with a simple test?

Thanks in advance  

It is unlikely to be the HBV as this would not, and in my experience, does not affect engine temperature.  You would also see water gushing down from the back of the engine if this has failed.  It is more likely failure of the secondary fan as you indicate.

However, I personally would also doubt / check the thermostate first, and then go from there.   Is there any oil in the water; has it changed colour?  Are you indeed losing any water? :-/ :-/   Any sign of where the steam is coming from; sides / front / rear of engine?
 :-/

[DaveyDavey]

Steam was gently issuing out from the back of the bonnet, which is why I thought perhaps it was the HBV given it's location.

I've not looked at any of the water tanks yet, didn't get chance too after I parked up as the few stops I made to get the temp down on the way held me up and I had to get in to the office for 9:00 to see someone.

I will however be leaving in about 5 minutes time to go and have a look at the water and also the fuse situation.

[mark.adams]

Mine was doing this for a while, creeping up to 100 before the main fan kicked in and cooled it, i unplugged and replugged the air con fan, now it runs at 95 and never gets hotter than that.
Just moving the connector seemed to have cured it

[V8S]

Mark, you're not the chap who works on V8 engines are you?

Long shot but hey...

[DaveyDavey]

Update:

Right well after the original overheating problem I found that I had no water in the tank(that'll be the reason then). The fans were working fine. So promptly filled it up with some of the finest council pop Bristol has to offer, ran the car for a bit on idle and topped up what had dissappeared.

After I had driven home again, I checked the tank and refilled what had dissappeared. Now at no point on the way home did I notice any liquid leaking onto the road and there was no cloud of steam issuing forth.  I had to go out again that night and when I had parked up I noticed a "scalded water" smell, which was fairly noticable to my two passengers as soon as they got out of the car as well.

Now that was a week ago and I have dilligently checked the water level before every journey since and it remains the same. Also the smell has not reappeared either.

Any thoughts on what on earth has occured here?

[Marks DTM Calib]

Mark, you're not the chap who works on V8 engines are you?

Long shot but hey...

Lol, the (supposidly) legendary ECU man!

[Marks DTM Calib]

Update:

Right well after the original overheating problem I found that I had no water in the tank(that'll be the reason then). The fans were working fine. So promptly filled it up with some of the finest council pop Bristol has to offer, ran the car for a bit on idle and topped up what had dissappeared.

After I had driven home again, I checked the tank and refilled what had dissappeared. Now at no point on the way home did I notice any liquid leaking onto the road and there was no cloud of steam issuing forth.  I had to go out again that night and when I had parked up I noticed a "scalded water" smell, which was fairly noticable to my two passengers as soon as they got out of the car as well.

Now that was a week ago and I have dilligently checked the water level before every journey since and it remains the same. Also the smell has not reappeared either.

Any thoughts on what on earth has occured here?

Its possibly the heater bypass valve which can leak intermittently and is also dependent on the temp settings etc.

Also, NEVER just add water, you need to ensure you aheva  50:50 antifreeze mix or you risk damaging the head gaskets, heads, oil cooler etc.

[Hog]

Agree with above make sure you have some coolant in there too or the water is likely to just boil and solve nothing. You may have a faulty hose, or a partial block in the rad somewhere. Often with small leaks you see no water as it is evaporated due to heat. You may get white water marks though

[ians]

Try standing by the drivers side front wheel and shining a torch in towards the HBV.   Even if not wet, if its been leaking you will see staining in the vicinity.

As Mark says, the leak mode of the HBV depends on temp setting and whether AC is on or not - so if you have been fiddling with the AC controls that may well determine whether you have a leak or not.

Interestingly I have a similar thing that happens in hot weather, esp in any kind of slow traffic temp will rise towards the red.  Turn off and on within a short time and the temp will have apparently dropped down the guage significantly.   My fans are all working ok - come on at the correct temps, and also the fact it runs hottish even at motorway speed suggests its not a fan problem.  Could be stat not opening fully (I doubt it) or rad losing efficiency.

Sorry - didn't mean to hijack your thread

[V8S]

Mark, you're not the chap who works on V8 engines are you?

Long shot but hey...

Lol, the (supposidly) legendary ECU man!

I'm intrigued by the 'supposedly', old stick.

[DaveyDavey]

Update:

Right well after the original overheating problem I found that I had no water in the tank(that'll be the reason then). The fans were working fine. So promptly filled it up with some of the finest council pop Bristol has to offer, ran the car for a bit on idle and topped up what had dissappeared.

After I had driven home again, I checked the tank and refilled what had dissappeared. Now at no point on the way home did I notice any liquid leaking onto the road and there was no cloud of steam issuing forth.  I had to go out again that night and when I had parked up I noticed a "scalded water" smell, which was fairly noticable to my two passengers as soon as they got out of the car as well.

Now that was a week ago and I have dilligently checked the water level before every journey since and it remains the same. Also the smell has not reappeared either.

Any thoughts on what on earth has occured here?

Its possibly the heater bypass valve which can leak intermittently and is also dependent on the temp settings etc.

Also, NEVER just add water, you need to ensure you aheva  50:50 antifreeze mix or you risk damaging the head gaskets, heads, oil cooler etc.

Guilty m'lud.  

I put in the water as I had nothing else available at the time. I've got some anti-freeze in the boot now though having picked some up earlier. I'll pop it in there later when I get home.

[dbug]

Possibly leaking HBV, amount of leakage dependant on your temp settings.  Whilst leaking HBV won't directly cause an engine to overheat - the subsequent loss of coolant certainly will.

[yorkshire ripper]

hi guys
when is the hbv more likely to leak, with aircon on or off. mine looks bone dry but obviously i cant see when im in the car driving with aircon on/off.ive got no overheating either. think im gunna change it anyway..
lee

[DaveyDavey]

Recap: Ten days or so ago the temp goes off the chart and further investigation reveals nothing in the expansion tank. So I filled it up with water and did a few short trips and there was no loss of water.

At the end of last week I drained all the water out, flushed it out with a bit more clean water to ensure everything was out and refilled with 50:50 water:coolant. I took the car for a spin round the block and then topped up the level as it had dropped slightly. Over the weekend everything was fine, did a few journeys and the temp stayed nicely just below 95C and the level of coolant remained constant.   Happy days.

This morning however on the way in to work, the temp started to climb up and hovered just under 100C. As it didn't go above this level, I carried on the remaining 1.5 miles to the office. I popped the bonnet and there didn't appear to be any coolant in the expansion tank when I gave it a wobble.

I'm thinking that for such a large amount of liquid to go missing, I must have a leak of some sort. Although there is nothing immediately obvious under the car. Which leads me on to the HBV? Does this thing dump out coolant on the sly? And what's the best way to check for a leak since it's positioned in such an awkward place?