posted June 23, 2007 00:19            

So here goes.

Does it lose water BEFORE any losses due to boil over? Yes. The Tractor blows water out before it overheats and starts to boil.

How quickly does it get up to boiling point? This varies to be honest. From under a mile on the road to a good 5 miles.

Does the engine show any signs of running a little rough? The engine is in near perfect condition having only done 4000 hours.

Blown head gasket? I replaced this and had the cylinder head reground.

Faulty thermostat? The tractor didn't have one in when I bought it. I have bought one since, but whether it is fitted or not, it still boils up.

Faulty water pump? I have fitted a water pump kit on the tractor.

Blocked radiator? Purchased a new one in the hope I could solve the problems!

Slipping fan belt? The fan belt has been renewed and is tightened correctly I believe.

Radiator cap not pressuring? The radiator cap has been renewed. I wondered if fitting a pressurised one would help matters, but I read that only export models had pressurised water systems.

Burnt valves not seating? I reground the valves when the cylinder head was off.

Brakes dragging? This is not a problem.

Do the answers to the questions help anyone identify a cause?

I ought to add the following. Two days ago I tested whether air was entering the system by sealing a thick plastic bag on the filler hose which came back showing that the system was not taking in air. The bag didn't inflate.

It's also worth noting that I have flushed the engine till the water runs clear at least 3 times.

Finally, the most recent "incident" is a strange scenario. I had successfully driven the dexta since the new radiator without a problem of boiling up, but water has blown out.

I then did a day's worth of topping last week and when it came to taking the topper back, the water started to blow out and the needle on the Temp. gauge started to climb into the red! Even though whilst topping I didn't have these problems! I was running at lower revs taking the topper back also, because it's a 2m cut heavy duty Bomford Turbo-cutter on the hydraulics and it doesn't half take the weight off the front!

After all this I am at a loss. Why does the tractor keep boiling up? Why does it blow the water out? And what can I do to solve it?

posted June 23, 2007 10:36               

You have replaced the radiator so that should have eliminated that.Did you fit a new radiator or a second hand one?

The radiator hoses cannot collapse internally there is not enough rubber in there to allow that. But they can collapse due to a faulty pressure cap and it can be seen as they all suck in. Yet you do not have a pressure cap. By the way it is not true to say that all export Dextas had pressure caps and all for the home market did not. We had plenty of ones around here with pressure caps fitted from new.

When you did your "bag check" did you seal the overflow pipe?

I suffered a similar problem with my Nuffield. It would loose water from the radiator yet there was no oil in the water or water in the oil. The radiator was clear and it had a new water pump. When I found the problem it was pin holes in the liners allowing pressure into the system but without the other normal indicators. Cracks and pin holes can also occur in Dexta blocks.

When you had the head repaired and did the valves, did you have it pressure checked?

Have you had the engine pressure checked? This can be done easily if you can borrow the pressure check tool from a local garage. It just fits on the radiator cap and inflates the system to a pressure and you watch to see if it leaks down.

You have covered most of the normal items so I would siggest that your problem is a fault in the bore or a crack in the head.

posted June 23, 2007 14:23            

In answer to your questions:

The radiator is brand new and not second hand.

The cylinder head. I wanted it crack testing but the owner of the place where I took it told me that he doubts it would be cracked. There also was no evidence of cracking.

For the bag test I had to take the actual overflow pipe and it's fitting off so the bag was sealed to the hose itself.

I think I may have to resort to removing the head again and have a crack test. It'll be a shame if the liners in the block are cracked as like I said, the tractor has done so little work the wear is minimal.

posted June 23, 2007 15:37               

Dan,
Its not the work the tractor has done its the time it has been "on this earth".

Your problem seems to be one that is building up over operation time when the engine gets warm/hot. That is why the crack/pin hole scenario is top in my book. It is opening under heat/load/stress. It would not be visible under cold conditions.

Failure in the head area is becoming a more common problem. You will find that Jos has had the same problem with an engineering shop. My man always tests for cracks before doing any work on the heads I take him. But he is an old timer like me!

posted June 23, 2007 18:08               

Let me start by pointing out that we are some 9 hours ahead of you here. So when I read your response sat morning, I had a better idea of your problem. My inital thoughts coioncide with Brian's and they still do. However, as I knew you were tucked up tight in your cosy bed, I decided to delay responding until I thought the problem through during the course of the day.

During that process, I was continually haunted by thoughts as to what happened to Jos when he got his (Dexta's) head job done!

I had been invited to go to some friend's place for a few "sherbets" and dinner and had to leave at 4pm. (Your 8am). I hadn't the courage to be the first to inform you about Cylinder Pressure to be the probable cause of your water blowing out. So I chickened out and left it to Brian, whom I was sure would say the same thing, but I was hoping that he had some other simple explanation and rememdy. I had read many threads about the Dextas having problems with cracked blocks but the way I had read them, they all seem to be leaks to the outside of the block and not to the Compression side.

The only other thing that I can contribute is to question about Re-Torquing the Head down. Did you (or whoever did the replacement) re torque the head down after running the engine until it was hot for a while?

It's now nearly 2 am here and 6 pm there and I hope you have a Saturday night as enjoyable as I have had!! (hiccup)

Now I must check in with the dear wife by phoning her in Bradford, Ontario, Canada some 15,500 Km away (and midday), and try my best not to slurrrrr my words

Cheers,

posted June 26, 2007 15:54               

While reading this , I could not get rid of something I noticed when I was re-installing the cylinderhead on mine.

When the head was off and at the "garage", I cleaned the entire water-side of the block.
The main reason is because I noticed that there was a lot of "mud"/"sludge" in the water in the engine.

I removed the water-tap at the engine side and started pooring in water in the different waterchannels at the top of the engine (with the cylinders closed by greased paper and the same for the oil-holes). That water was collected in a big bucket and from time to time I had to poor away the water. With a long flexible hose (6mm thick) , I scratched her inside and cleaned all channels around the cylinders while water was in. After about 2 hours and about 70L water, I got about 3 liter of rust, mud and other sediments in my bucket.
So,might be that your engine is full of sediments or in worst case, there is no circulation at all in the engine.
The engine may fill up but the bottom-hose is closed (inside the engine) so, at a certain temperature , the water gets hot enough to start boiling.
This higher temperature can not be measured by the temp-sensor above the waterpump as there is no watercirculation over the engine, so you will not notice.

My advice is
1) open the watertap at the engine side and see if the water is floating out.
2) Remove the thermostate, remove the bottom-waterhose (at the engine side,) try to close this hose and poor in water at the top of the cooler. The water should float through the engine quit rapidly. This would proove that the engine is clean or not .

Hope it helps.

rgds
Jos

posted June 28, 2007 01:53            

When I filled the system again there is definate gases getting into the system and bubbling out the top. The next step is to strip the tractor down and check both the head and the block. Sadly due to lack of workshop space, the Dexta will have to wait in the queue.

posted June 28, 2007 07:21               

Jos