AAZ Thermostat issue?

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mrnickmuss
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AAZ Thermostat issue?

Post by mrnickmuss »

My Doka seems to be battling me! A long post but please read if you know anything about cooling systems and please then tell me what I am missing!
I thought I had it sorted after recently replacing the engine I have done a fair bit of chasing niggling issues that have driven me mad and have mananaged a fair bit trouble free motoring but have been stumped by an ongoing issue.
Under normal load and taking it easy it runs fine. If I put it under any strain it runs hotter than my old engine. (thought this migh have been the timing which was a tooth out but is now sorted) Replaced thermostat with lower temp one from .
Iast week after driving for around 40mins I watched the temp gauge climb beyond comfortable so I pulled over and checked the expansion tank which was at the correct level.
I then checked the tank directly above the engine and it was low. but the water in it didn't seem excessively hot. However I managed to get 1.5 litres of liquid into it. .The cab heater was blowing hot air. The radiator was warm but not hot.
I drove another ten minutes home without a problem.
I started it the the following morning and ran it up to temp checked the radiator which was warm throughout and then drove it steadily to work.
I got to work checked the radiator all fine, checked levels all fine.
At the end of the day I saw a small damp patch on the ground, got underneath and saw a pipe near the front was weeping.
So again checked water levels all fine. Drove home and just as I arrived home it started running a little hotter.
So yesterday I got it up on my friendly mechanics lift and replaced the jubilee clip. Checked the darlec cap which blows freely through one way but not the other.
I then ran it up to temp and bled the system. Very little air came out. the raditor was heated evenly and I topped up the expansion tanks.
Today I drove it 30mins to pick up some firewood. I watched the temp gauge move steadily upwards on the hills and then back off on the flat. As I was arriving at my destination I watched it climb fairly sharply. I jumped out of the cab to see steam gently rising from the back.
I discovered a hose was leaking in the engine bay.
I then felt the radiator which was stone cold! So were the return pipes.
I decided the only safe way forward was to take the thermostat out. I restarted the engine and all the pipes ran luke warm which showed I gad circulation. It ran very cool all the way home with a load of wood in the back up some quite steep hills.
I obviously cant keep it running like this but I am stumped as to why it is over pressuring and the thermostat is not opening even after bleeding?
Any suggestions?? It is probably something obvious but I am missing it!

windy
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Re: AAZ Thermostat issue?

Post by windy »

Sounds like you have had a series of hoses leaking which have likely lead to air locks.
These vans are a pig to bleed the air out of even without leaks!
See the wiki regarding correct bleeding & be aware that the AAZ really needs an additional oil cooler, although this probably isn't an issue at the moment
Mark.
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mrnickmuss
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Re: AAZ Thermostat issue?

Post by mrnickmuss »

Thanks Windy...
Wiki has become my bible. I have followed the proceedure religiously on a number of occassions and thought I had become proficient at it.... But my question to mechanic friend yesterday was: 'If the radiator is warm to the top and all the pipes are warm, surely its bled correctly? ' He said it was..... So I drove off feeling quite smug with myself... how wrong was I?
Yes I have resigned myself to shelling out for a cooler but the temperature here at the moment is pretty cold so thought I have a bit of time to save my pennies!

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Re: AAZ Thermostat issue?

Post by ZsZ »

Which thermostat have you used? The AAZ or the JX?
The AAZ has higher opening temperature.
Beside that it is not unseen that new thermostats are bad and stucking.
Try out with a known good thermostat.
Zoltan
1986 Multivan ex-Caravelle. Van since 2006, running mTDi 1Z since 2008 with Fiat Croma 1.9 TDid pump 2008-2019, custom pump since 2019
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mrnickmuss
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Re: AAZ Thermostat issue?

Post by mrnickmuss »

I have used a 80 degree one from brickwerks

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Re: AAZ Thermostat issue?

Post by MGP »

Which radiator is fitted? The aaz engines do need the one with the 44mm thick core, also how old is it? Radiators silt up over time, if yours is the original then it will have lost some of its efficiency.
As the water in the coolant expands it pressurises the system, the pressure is regulated by the pressure cap, as the water cools it contracts if any coolant has been pushed into the overflow tank then once cool there will be a partial vaccum in the system and coolant will be pulled in from the overflow tank through the valve in the darlek cap (the one you have tested). If the darlek cap is not holding the correct pressure (1.1 bar) then it will overflow the overflow tank and also allow the coolant to boil causing air locks whilst driving.
You say the overflow tank was still full but the expansion tank was low, as you will have noticed when testing the darlek cap it takes a bit of force to draw the coolant back into the system, if you have a leak in the system it is often easier for air to be drawn in through the leak than it is to pull coolant in through the darlek cap.
Do you know which water pump you have fitted? And which belt setup are you using? There are two water pumps fitted to these engines dependant on which belt setup you have, the each need to be run in different directions.
Check that the turbo is boosting correctly, if you are not making enough boost pressure then you will have higher than normal egt's which will put more strain on the cooling system, I have the 80 degree thermostat in my aaz, it will be being replaced for the 87 degree one when I get time as mine never gets hot and I want my decent heaters back.



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Re: AAZ Thermostat issue?

Post by mrnickmuss »

Thanks MGP for taking the time in replying. You have provided me with some great info for me to get my head around! It originally had a JX engine so I am guessing it has the right radiator. I have no idea how old it is. It looks in good order externally and warmed up evenly when I was bleeding the system. But I guess you cant know what is really going on inside!
I will check out what water pump it is running.... I know it was an earlier AAZ I still have my old lump (which is a later version so I may gave have some spare parts if required)
Are you running an additional oil cooler? If so which one?
just when I thought I had enough knowledge to keep my Doka on the road I now realise there is so much more to learn!

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Re: AAZ Thermostat issue?

Post by MGP »

Checking that the radiator warms up evenly isn't a reliable test as it warms too slowly, a more reliable test is to get the radiator hot preferably without a thermostat fitted, keep the revs up and bridge the fan switch, with the fan running now check that there are no cool spots on the radiator, you will most likely find that the lower 1/4 will cool off almost instantly, if this does happen it is due to low water flow because of partial blockage.
I am running an oil cooler, it is an Oxford hydraulic oil cooler fitted in the bottom of the d pillar, the air is ducted through the bottom of the tray out to the rear valance, I also have an intercooler fitted the same way on the near side.
I am also running a far more efficient turbo and a better flowing exhaust manifold which helps to keep temperatures down, as it is I am currently unable to get my oil temps to 100 degrees.


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boatbuilder
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Re: AAZ Thermostat issue?

Post by boatbuilder »

Maybe your dalek cap isn't working right. Even if you can blow through it, that's no guarantee it's working at the correct pressures.

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HarryMann
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Re: AAZ Thermostat issue?

Post by HarryMann »

Yes all good advice there [THUMBS UP SIGN]
Oil cooler is a non issue atvthe moment.. when you get to it 18 row up front minimum pref. 24 row Mocal style.

Messing about with thermostats prob. not a good idea. Just use the correct one (87C ?)... opening slightly earlier or later is of little import once its up to temp.
Temp gauge will always climb when working hard or stationary and fan stage 1 at least come on... stage 2 really only very hot and high climbs abroad.

Does sound like Dalek cap, another weep leak, head gasket or crack in head.
Don't overtighten those jubilee clips. Def check water pump !
Ih maybe check hose between the 2 tanks... mine nearly fretted through rubbing on something!


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Re: AAZ Thermostat issue?

Post by mrnickmuss »

Thank you to you all who have contributed. My Doka is also my workhorse. I run an organisation working with special needs and sensory impaired children and now refugees. We get them out of the classroom and out into the great outdoors. I have been building a log cabin today with a group of Deaf and Autistic young people....Without my Doka things would become very difficult. I have a sturdy Swedish electricity board box on the back so I can chuck anything in or on it. I would hate to give up my Doka. There just isnt a modern equivalent... If it had been a modern van it would have been long since scrapped as I wouldnt have been able to afford the bills as at least most jobs with a bit of help are doable on my Doka!
To clarify and to gain a consensus of opinion.....
Check pump... (however from reading earlier threads if it was running the wrong way it would warm up the radiator? Which it has when I was bleeding it, so mine is OK? can any confirm this?
Check Turbo.... Dont know how to do this but will ask my friendly mechanic...
Replace thermostat with 'normal 87degree one.... (although Brickwerks recommend otherwise? I would be interestested to hear others experiences of running either.)
Check pipe between the two tanks.... I know mine is a little suspect as I am unsure that the spring clip does seem relatively easy to release. How tight should this be? How are other peoples attached? Also what diameter is the pipe?
Darlek cap..... how do you test reliability?
Any opinions happily received!
Bleeding... Up at front, or back or both or on the level?????
Any opinions greatfully received!

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Re: AAZ Thermostat issue?

Post by ZsZ »

On my Tdi I lowered running temperatures (and fastened the heat up) by bypassing the aux pump with a piece of pipe. Then you have an always working oil cooler, not just when coolant is above 102C
Zoltan
1986 Multivan ex-Caravelle. Van since 2006, running mTDi 1Z since 2008 with Fiat Croma 1.9 TDid pump 2008-2019, custom pump since 2019
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HarryMann
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Re: AAZ Thermostat issue?

Post by HarryMann »

Maybe just try a known good Darlek cap. Never had to raise the front to bleed my AAZ out. But at least have nose up slope if there is one.

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Re: AAZ Thermostat issue?

Post by mrnickmuss »

Tested my 80 degree C termostat last night with a termometer and hot water .... question is how far should it open? only opened up about 5mm. even if I took it a few degrees higher.
Any thoughts????

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Re: AAZ Thermostat issue?

Post by MGP »

the thermostat, the temperature stated on the thermostat is when they start to open so an 80 degree stat won't be fully open until they are around 85 degrees maybe a touch more.

the water pump I forgot to mention before its not unheard of the impeller to loose it's grip of the shaft, so it will pump enough water to keep things in check when there is little demand on the system but can't keep up under load.
The pipe between the tanks needs to be perfect as does the rest of the system. The pipe between the tanks needs to be air tight not just water tight, I use 6mm silicon as it makes a good seal with no clips.
The darlek cap needs to be checked with a pressure tester with the issues you have been having it may be a good idea to pressure test the entire system.
Bleeding is simple, all you are doing is heating the coolant so that the water expands, compressing the air trapped n the top of the radiator and releasing it via the bleed screw, no lifting involved.


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