Coolant probs - solved (for now anyway)

[diesel dunk]

Today I swapped the hoses back to the stock set up (hot going in at the bottom of rad) removed the thermostat and bled the system really carefully - which I had done anyway. The coolant gauge takes about 5mins longer to get to the middle without the t-stat in place, but IT STAYS THERE!!!!! Hooray.... For the first time, whichever way I have had the rad connected, both pipes are hot and the rad is hot and doing some work at last. Therefore, I suspect that the gauge may be ok and now the system is working better. It may be that the water pump is warn, but there is plenty of turbulance in the expansion tank now, and although I tested the thermostat b4, without it blocking the circuit there now seems to be enough pressure to pump coolant up the front and round the rad.... I plan to leave it like this unless anyone strongly advises againts running without a t-stat. - let me know....

Cheers,

Dunc.

[myke_w]

perhaps the stat was in backwards? Also, cool (as in not at operting temp) engines run inefficiently. Sounds like the stat was either malfunctioning or in backwards to me..

[libbybapa]

Yup I'd fairly strongly suggest not running long term without a properly functioning thermostat. When working properly the cooling system does a very good job of regulating the temperature of the coolant entering the engine. Running too cool will not boil water out of the oil, will reduce the efficiency of the engine and will also reduce the efficiency of the radiator. Overheating is only slightly worse for an engine than overcooling. Your gauge may still be a bit funky 90 should be fine for water temp.

Andrew

[diesel dunk]

just taken her out for a spin to do tests and here goes - the gauge needle takes 10mins to get to the middle, it stays there or even goes down a bit if I am going fast (lots of air over radiator) stopped somewhere and removed expansion tank cap and measured temperature - 57max. I assume this is not right. It was 91max with the thermostat in and the needle went right top the top of coolant gauge. However, with the t-stat in there wasn't enough flow to push coolant right through the rad. system. So, I think next I will replace the t-stat, although, my dilema is that with the old t-stat - the temp measure ok at 90, but the rad circuit didn't seem to work, so I don't know what is at fault? If the new t-stat works better then it will increase the flow and keep the temp at 90 still, but this doesn't make sense, as more flow = cooler liquid, as I have proved with the t-stat out? Any help on this. PS is the temp at the expansion tank the best place to measure (the only place I can think of) There also seems to be more oil in the coolant (my thermometer was covered in it)

[stopping]

I don't think your done yet.

You have yet to prove you do not have a head leak.

Here is another (better) test as discribed by Fatmobile elsewhere on this site.(In my own words)

Start the engine cold or with no pressure in the coolant system. With the exp.tnk cap closed firm let idle for 15 to 30 seconds. Unscrew cap and listen to it carefully. If air hisses and rushs out you have a leak.

Did you say you had done the head gasket? If you have you may have a cracked or warped head. (Over heated and maybe over cooled)

Imagine taking a cast iron frying pan from a the icey temps of -15C and dropping it on the raging coals of a bonfire and tapping it with a hammer.
Even the frying pan cracks.

This what is happening (as a friend described to me) in you motor when you start it. You cannot rev it up cause it's like hot fire on one side of the head and colder than ice on the other.

Having all cold water all the time maks this problem more dangerous.

I think (again) your Thermostat was in backwards, malfuctioning or your impeler it screwy..... you may have a head leak or all of the above.

Is you expn.tank original?
May be you could also say (out of curiosity how far it is from the water level in your expn.tnk.(cold) and the top of the tank and ... while your at it ...how far it is from the cold water level to topside of the engine area deck. The tank should be as high or higher than the OEM tank.

Can your put the details of your engine and van in your footer signature please. And maybe what region of the world you are in. I don't understand how you can get that thing so hot at this time of year.

[diesel dunk]

Hi stopping, I didn't think that the t-stat would go in backwards. There isn't enough room in the elbow of the pipe. Anyway, the expansion tank is the highest point in the engine bay. I was amazed that the coolant temperature went from 91 to 57 without the t-stat. I thought that by removing it I was simulating what the system would be like when it was in place and fully opened, so a drop of over 30deg - wow! I might have lots of problems with the engine that are harbouring under the surface, but it only has to last another year b4 replacement for something more powerful, and it actually sounds quite healthy, I just suspect it is running too hot and couldn't understand why hot was getting to the rad and freezing cold coming from it. It didn't sound right. Removing the t-stat has reversed the problem. I have just ordered a new one. If the coolant temp should be around 90deg C and the gauge needle should be in the middle at this temp and the expansion tank is the right place to measure then the gauge is faulty - or the wiring. The fact that it runs cold with the t-stat out tells me that the water pump is doing it's job too.

[stopping]

Touche.... sounds like your pump is working.

Isn't it cold across the pond this year?

More powerfull?.... if you know anyone who can translate german there is the best descrition of an AAZ swap avaliable.

You can find through
http://www.bullisurfers.com/

This is what I used... but I used a Google translation if you can believe that...... very difficult mental space in which to be consumed.

Maybe if you find a version in your research you could you culd post it for everyoe else. Those guys are great.

About your van....

Sounds like your tank is good. What about the leak? Anyhow Thanks for doing this research for all of us. It's interesting. You should refer to the Bentley manual for temp/ gauge specs.

You can tell how good the motor is when you (try to) start it.

[libbybapa]

87 deg thermostat is what really ought to be in there. That thermostat will only start to open when it is immersed in 87 deg water. You were measuring 91 at the exp tank. At that temp the thermostat will stil not be fully open, as the water in the exp tank still flows down and mixes with that coming from the radiator and then that water flows around the thermostat. It will not be full open until that water and that coming from the radiator is both at 105 C. Without the thermostat open fully your flow was reduced and your flow slow through the radiator circuit and rightfully so.

As I said before, I would still say that your gauge is funky, either the sensor, guage itself or wiring. It really shouldn't have been high on the gauge at 90 in the exp tank.

Andrew

[diesel dunk]

Thanks guys - I will put the new t-stat in as it is only cheap, and see what happens. Libbybapa, I agree now that the gauge must be wrong (or wiring) because everything now leads to that I have a new one on the way. Stopping, it is snowing one day over here and the next it is lovely spring sunshine - very wierd at the mo. not really the best for carrying out tests on coolant. Libbybapa posted a really good set of pics on an earlier post I started on this forum about fitting AAZ into a vanagon and I will look at that site of yours too. Cheers people. Will let you know how I got on.