Does this sound like a head gasket problem?

[jimmo62]

My 1995 2.5TD Auto AFT Bongo dumps coolant out of the overflow pipe on the coolant header tank but only some of the time.

I'm pretty sure it is not leaking coolant anywhere else because I am catching the overflow and tipping it back in (coke bottle wedged in behind the leisure battery!) and the level looks OK - so I'm not losing much if any coolant. The pressure in the cooling system holds up well (still a noticeable hiss when opening the cap after several hours post driving). I had a new radiator, thermostat and pump fitted by a well known Bongo garage and the owner there who knows his stuff did not think it was the head gasket (none of the usual symptoms). I have assumed he has done a good job of bleeding as he is very experienced.

It only happens on very hot days - I would have thought a blown gasket would do it all the time on long runs? All 3 fans seem to come on OK. I have an aftermarket (not Haydn I'm afraid) head temp gauge which shows 85 on a run at speed, up to 95 on steep hills and at the weekend when it was very hot it hit 102 after I stopped and turned off the engine - all with no leakage. Sensor is bolted to the threaded hole in the head just behind the oil filler cap.

But the previous week when it was used by my better half in heavier traffic it dumped about 250ml.

So could it be a head gasket and if so why isn't it doing it all the time? Or could it be the fans are not coming on soon enough in very hot weather? Or a blockage in the coolant circuit? Something else?

I'm trying to catch it in the act so I can look at the fans and head temp but of course it won't do it when I am looking!

Any ideas of what to look at next to try to debug it? Is a head leakage detector kit worth a try (the sort which detect exhaust gas in the coolant)? Maybe wire up LEDs to the 3 fans to see when they come on? What's a logical sequence of investigations/tests?

thanks!

Jim

[Steptoe]

Jim,
What temp guage do you have? I'd like to install one myself.
Thanks,
Steptoe

[Gasy]

There is a few on the market
The ones I have heard of being used on here are

Haydn does a few models ( member on here ) search for tm4, well recommended on here.

I have this one of eblay not gave me any probs item number 111052553849

Well worth it

Do remember to occasionally look at the road tho when driving not just the gauge

[g8dhe]

Could be the wrong cap or a weak spring on the header tank cap?

[Bob]

If you're stuck try ADS in South Liberty Lane.

[Northern Bongolow]

im with geoff, try a new cap on the expansion tank.

if that doesnt fix it then replace the fan switch just above the starter motor. if the cap is blowing early and the fans coming on late then you could see your symptoms.

[jimmo62]

Great, thanks guys I will try both suggestions and let you know how it goes. Just need to hope the hot weather holds on for a bit longer!

[The Great Pretender]

My 1995 2.5TD Auto AFT Bongo dumps coolant out of the overflow pipe on the coolant header tank but only some of the time.

I'm pretty sure it is not leaking coolant anywhere else because I am catching the overflow and tipping it back in (coke bottle wedged in behind the leisure battery!) and the level looks OK - so I'm not losing much if any coolant. The pressure in the cooling system holds up well (still a noticeable hiss when opening the cap after several hours post driving). I had a new radiator, thermostat and pump fitted by a well known Bongo garage and the owner there who knows his stuff did not think it was the head gasket (none of the usual symptoms). I have assumed he has done a good job of bleeding as he is very experienced.

It only happens on very hot days - I would have thought a blown gasket would do it all the time on long runs? All 3 fans seem to come on OK. I have an aftermarket (not Haydn I'm afraid) head temp gauge which shows 85 on a run at speed, up to 95 on steep hills and at the weekend when it was very hot it hit 102 after I stopped and turned off the engine - all with no leakage. Sensor is bolted to the threaded hole in the head just behind the oil filler cap.

But the previous week when it was used by my better half in heavier traffic it dumped about 250ml.

So could it be a head gasket and if so why isn't it doing it all the time? Or could it be the fans are not coming on soon enough in very hot weather? Or a blockage in the coolant circuit? Something else?

I'm trying to catch it in the act so I can look at the fans and head temp but of course it won't do it when I am looking!

Any ideas of what to look at next to try to debug it? Is a head leakage detector kit worth a try (the sort which detect exhaust gas in the coolant)? Maybe wire up LEDs to the 3 fans to see when they come on? What's a logical sequence of investigations/tests?

thanks!

Jim

Does it dump coolant when running or when stopped and residual heat builds up? This should be noticeable from the ‘coke bottle’ if empty as soon as stopping.
If you extend the pipe from the tank into the bottom of the ‘coke bottle’ the dumped coolant will re enter the cooling system automatically as the system cools. Instead of letting air in as the standard system does.