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Topic: 24v RAD PROBLEM (Read 910 times) |
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Tobbe
Junior Member
4.1 litre 24v BOB
 
 
Posts: 93
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24v RAD PROBLEM
« on: Sep 1st, 2006, 8:13pm » |
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Continued from the scorpio list.
A little summery for those who haven’t read the mailing list.
My 24v suffer from the ballooned rad syndrome, I thought a new rad would do the job. But after when fitting a new one small drops of water was coming of the lower hose connection on it, thought it was the old clamp that was no good, but it was, it was the side tank that had come off, got a new rad from ford under warranty, inspected it in its box at the FMD, the side tank was already loose on that one, got yet another one, the tank came off after a 10 days, got another one that have not been fitted yet.
Confused about the problem I started to measure the pressure in the rad and in the vent-pipe coming from the housing placed in the V. The readings told that the pressure was variated due to my rpm…
First there is a “heat” pressure, approx 0.5 bars at normal working condition. And to this there were also a pressure increase of 0-0.5 bars depending on the engine revs, so basically the pressure is minimum 0.5bars and increasing to 1bars at full rpm, I would suspect that this variation in pressure causes the ballooning of the rads due to fatigue. The heat pressure is a bit depending on how hot everything is so it can be a bit higher or lower from time to time, but the “rpm” pressure was always the same.
The relieve valve in the cap is set to open at 1.2 bars, which it never have done, just to be safe I bought a new one. Still it never opens, i.e. the pressure in the expansion tank never exceeded 1.2 bars. Also the gaugers told this.
What can cause pressure in the system?
1. Heat
2. Flow restrictions
3. Blown head gaskets
These are the things I can come up with.
I think I can rule out number 3, no water in the oil, no white smoke, and if compression would leak into cooling system I would expect a higher pressure increase which would be a function of engine load and not just the rpm. So I don’t think this is the issue. But I must admitt that I have not made any sniff test in the expansion tank.
Number 1 then, if I start my car from cold, and rev it up as soon as it have started, there could not possible be that much heat transfer to create the variation of the pressure in the cooling system. So I don’t think this is causing the trouble either.
Then we only got one left… As it is today I have modded my cooling system a bit and now I got reasonable pressure readings in the radiator but still the pressure in the engine varies just as much as before.
When the side tanks have come of I have always put back my old balooned rad and after reinforced that one it have always worked ok, but it does look really nasty, I've used it for at least 30 000km when it was ballooned, and probably much longer, I've just haven't noticed it.
It would be really interesting if someone that has suffered from the ballooning syndrome could make some pressure readings and also from some on who hasn’t.
Any ideas what might be causing the pressure problems are very much welcomed, all hypotheses. Why the side tanks came of is a quality issue on the rads I think, when compared to my old on you can tell that it's not the same quality on them where they are pressed to the tanks...
I’ve took a short cut and draw the cooling system on paper, I’m not 100% sure but almost that it’s like this the 24v is connected.
 
I hope if I didn't draw it correct some one will correct me..
//Tobbe
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Geoff_W
Senior Member
98 Ulti2.5tdi Auto
Posts: 1340
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Re: 24v RAD PROBLEM
« Reply #1 on: Sep 1st, 2006, 8:39pm » |
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Tobbe,
Baz was troubled by several pregnant radiators and I also seem to remember that a number of people carried out pressure measurements when theirs popped, so there should be a swarm of folks along any minute.
Incidentally has anybody with a 12 valve experienced the same problem?
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The winding road goes on and on... or at least it does in Northumberland
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howiedintheplace
Senior Member
Based near Evesham
Posts: 1194
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Re: 24v RAD PROBLEM
« Reply #2 on: Sep 1st, 2006, 9:49pm » |
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Well done Tobbe.
There should be some pressure in the water system but what pressure is O.K I don't know?
I think the rads have a weakness personnally.
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Dave
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #3 on: Sep 2nd, 2006, 8:42am » |
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One would serioulsy think that if the pressure is kept below the relieve caps opening pressure of 1.2bars you would be safe, but you are not as it seems, at least not for me with new my rads.
What will could create that pressure variation? Is the pump characteristica all wrong for this engine, i.e. pressure vs flow? Maybe one should pay some attention to the pump, the gear ration on the transmission to it, the impeller diameter. Maybe checking theese things out and compare it to an 12v or maybe an BOA could tell if the flow is much bigger on the 24v, this might cuase the pressure variations I think. But it would be of big interrest to know if thoose who have not suffered from ballooned rads also got variation in pressure due to the rpm...
I did some pressure readings in a granny mkII 2.8 rad, in that car the pressure is constant 0.5bars.
As seen with these formulas you can so how big differ a little change in impeller diameter does, and also the rpm of the impeller. qv=flow H=pressure. As seen a change in impeller diameter got the biggest effect on the flow, a change in gear ratio got the biggest effect on the pressure, maby it would be worth to make a little bigger pulley for the pump in order to decrease the impeller rmps and lower the pressure,it will show on the pressure readings if it will have any effect... Well I've just got to test it, otherwise I will never know.
 
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howiedintheplace
Senior Member
Based near Evesham
Posts: 1194
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Re: 24v RAD PROBLEM
« Reply #4 on: Sep 2nd, 2006, 9:04am » |
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The pump ratio to the crank & impeller size is the same as the BOA & 12V engine.
What's different is the pump casing, in fact I think the above is also the same as the 2.8 but I am not sure on that.
I think the problem is with either the rad or the way it's all connected together.
Dave.
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Dave
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #5 on: Sep 2nd, 2006, 9:17am » |
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If I could get rid of the variotion of the pressure I would be happy, I must try something, a pulley could be made in just a few minutes so I will try that one and see what happends.
Dave, do you know how the BOA coolingsystem is connected? I'll have a closer look on the 12v cooling and se if I can hook every up like it is on that one... And also see if I can make some readings from some other cars and see if they also got this variation i pressure.... The hose running under the head really scares me.... I'll see if I can lathe and mill a new housing for it without that hose connection.
Besides, I am stuck with my new low quality rad, and the fmd told me this was the last time there would be any warranty replacement. So I need to sort this out somehow, but experimental is fun too.
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Baz
Moderator
Senior Member
S Reg. 1998 24v Cosworth S2.9 COS (Deceased)
Posts: 4009
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Re: 24v RAD PROBLEM
« Reply #7 on: Sep 3rd, 2006, 12:08am » |
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I just changed mine when they needed doing.... a lot easier than trying to work out why they break in the first place I guess!!
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #8 on: Sep 3rd, 2006, 7:04am » |
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Dave, thanks for posting the pictures.
Baz, with the quality on the rads I've got I would need the replace one every 10th day, I can't afford that  .
Maybe I should be satisfied with the modded system and just make a new hosing without the stupid hose running under the head. It won't kill my rad tough.
Bit still, it doesn't take much time to test a bigger pulley either..... It could be a good learing to see what happens with it...
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howiedintheplace
Senior Member
Based near Evesham
Posts: 1194
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Re: 24v RAD PROBLEM
« Reply #9 on: Sep 3rd, 2006, 9:22am » |
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Tobbe if you blow another rad I would get a 2nd hand one from either a 12V Scorpio, 24V BOA or diesel Granada & fit that.
Then just tap in the missing pipe join or re-route it.
Once water is heated & pressured it does funny things that are hard to figure out.
Also don't make the pulley too big else the water might boil in the head & then you will have a gasket problem.
Good luck.
Dave.
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Dave
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #10 on: Sep 3rd, 2006, 5:25pm » |
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Dave, I wish I knew that earlier, would have saved me some money I'll have a look for an used 12v rad then.
I discovered that the pressure on the "high" pressure side was getting almost 2,5bars now at max revs when the system is modded, this is not acceptable, the hoses will probably go, I did never measure there after the mod, I just watched the hose and could see that there still were variations in the pressure. I guess the vent pipe is to small but fitting a bigger one is no use since it will not allow the engine to heat up, so I will try a new idea on monday or tuesday, run the car without the stat and increase the expansion tank volume with 0,5 liters and 1,5 liters. Will try get the time to make a new cap which allows me to attach a pet-bottle to it and see what happens... Should be interresting..
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freddieboy
Full Member
Juan Sheet does Plenty!
Posts: 291
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Re: 24v RAD PROBLEM
« Reply #13 on: Sep 14th, 2006, 3:30am » |
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Looking at this from another angle. I have a 2.3 which blew a radiator completely. This happened on a very hot day,when I parked up and a couple of minutes later there was a loud thump and a lot of water on the floor.
I emptied the account and bought a new rad and and fitted it,but I was concerned to know why the original one had failed. After many tests I discovered that the nearside rad cooling fan was not working at all,and probably had`nt been for some time. After replacing the relevant fuse the fan worked perfectly and no problems since. My theory is that the excessive heat coupled with inefficient cooling caused the rad failure. The problem is that you cant tell whether the fans are working without a visual inspection.
Conclusion? a 20p fuse could have saved me £380 
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #14 on: Sep 15th, 2006, 6:25pm » |
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My faans works ok, did also check a recently OBD II scan, the CLT is also ok.
Dave, where do you get all these pictures from? I am starting up the BOB capri TT on sunday for the very first time, it's not close to be finnished but I want to hear it run with thoose pistons before I strip the engine down but I will take some pressure readings from it and compare it with my scorp.. This 24v have new gaskets and reworked heads so there shoudn't be an issue with blown gaskets. I've not yet tested with a bigger pulley to see what effect it has in the pressure, I hope I do some interesting findings on my other 24v...
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hellblue
Full Member
Ill have silver,it dries just as fast !
Posts: 210
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Re: 24v RAD PROBLEM
« Reply #15 on: Sep 15th, 2006, 10:36pm » |
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Dont know if you have checked this (or if its on/in yours)but i had trouble with the cooling system on a sierra it ended up that in one of the small hoses to the bottle is a piece of brass pushed up it with a small hole (about 1mm)to restrict the flow this was blocked ! ford did/do this on other cars too my old diesel escort had one too,just a thought?
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Gary
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sector-9
Senior Member
No scorpio anymore
Posts: 1069
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Re: 24v RAD PROBLEM
« Reply #16 on: Sep 17th, 2006, 2:02pm » |
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Looking at the layout diagram for BOB engine, why is there a small bore pipe connecting the bottom of the radiator to the top of the expansion tank? Perhaps it's just drawn wrong and different in real life, but I can't see the need for it being as there already seems to be a vent hose connecting the rad top hose to the top of the expansion tank. In fact, if you imagine the surface of the water in the expansion tank is a piston which moves upwards with heat, then you can see from the diagram that the radiator is being pressurised from both ends (we'll assume the cooling system is full of water and therefore incompressible) - bit like a hydroelastic suspension setup..?
My old Rover 620 diesel uses the same type thermostat (as do several Landrovers) with no problems, but I'm sure mine didn't have a hose connecting the bottom of the radiator to the top of the tank.
Of course, it's highly likely I'm talking crap but I suppose the only way to know will be to take some pressure readings with that hose clamped shut...
Darren
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pappa
Full Member
VM Diesel 2.5Tdi 90kW
Posts: 259
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Re: 24v RAD PROBLEM
« Reply #18 on: Sep 18th, 2006, 3:06pm » |
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Hi guys! A week ago just finished with my (1st & last ? ) balloon. I took my new balloon from the -91 2.9 V6 I recently dismantled. So far so good, everything have (I'm grossing my fingers here) worked out just fine.
The old one had a lower hose that had lead into the "pressure tank" and I just
re-routed my 24V Cossie's pipe into it, hoping it would work. And so far it have
done it's job!
Pictures available on demand.
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My cars are the best and the pigs and cows fly.
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Tobbe
Junior Member
4.1 litre 24v BOB
Posts: 93
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Re: 24v RAD PROBLEM
« Reply #19 on: Sep 18th, 2006, 5:21pm » |
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Papa, can you make some pressure readings from the vent pipes? Just hook up a guager to the connections on the expansion tank. These hoses are just for evacuating air so the engine won't run hot on you..... I got a brand new rad, and I want to use it.... But I can't, my old balloned one works ok.......
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