Does water normally boil on the outside of the headgasket ?

[stopping]

Yes that's me Mr Waldon.

It might well have an air lock somewhere but man is it persistent.

I thought it was an engine issue at first and that's why I posted here. Maybe I will try asking over there at the Vanagon forum if my fishing trip doesn't yield results.

[theman53]

*quote*
Thermos were tested. I am now running (trying to run) with a Saab thermostat that opens at the same rate as the VW fully blocks the by-pass and allows more cool water to pass when it is open fully due to a larger orifice. *quote*

I don't know if this isn't the problem. I did something different like this once an had horrible trouble. I cut the center out of a vw thermostat once in my old rabbit. I drove it maybe 3 miles and the gauge was almost pegged and the water only was boiling in the coolant res. I know not to run no thermostat, but we used to do this trick in our mud toys all the time, but they were ford and chevy gas. If you ran no thermostat they would overheat, but if you cut the center out it restricts it enough to cool properly....just no heater. Not so for vw rabbit. I put the new normal vw thermostat in and it worked fine.
    Might try going back to the original, just a thought.   Jimfoo also had a modded thermostat in one of his engines, but you'll have to go to the faq or ask him on that. Hope it helps Lucas ><>

[stopping]

the Saab thermo is almost the same as jimfoo's mod. It has the small spring and the slghtly longer travel... the bypass disk is smaller than stock but it still blocks it fine.

The only difference the saab thermo has made since trying it out yesterday afternoon, is it has prevented the engine from overheating for a bit longer and it comes back cool sooner so I thinkn it is better...  I will of course go back to stock to see what the difference is... later today maybe. I am still chasing air and blockages for the moment.

My latest thought is that water around the per-combustion chambers is producing air pockets enough under load and that it air locks the rad as soon as you get to high rpm.

[stopping]

So I think the problem is related to the coolant manifold I made combined with not quite the right thermostat for the van.

I copied what was there almost exactly but the issue could be that I have a bleeder from the top (head) hose out (the highest point) to the expansion tank that is too restricted. The size of the tube is slightly larger than the restricting orifice in the stock hose but it is longer. The engine produces more heat than the 1.6 and has the vanagon specific cooing needs... meaning the there can a lag in the system since there is so much water to heat up. I think what is happening is that the thermostat is getting cooled by either the heater water or it is cooling too much in the expansion tank. The thermo opens too late due to the slightly cooler water circulating over it despite the influence of the by-pass.

The solution should be to enlarge the tube to the expansion tank and be sure it remains the same temperature as the engine. The restriction is seems is only for the efficiency of the heater.

[stopping]

yup... problem solved.... for you folks out there driving AAZ's with the stock 1.6 system with the restictor in the hose to the expantion tank... change it!

The engine temp is on the pin now after heating it to peak temp and driving uphill at 120km/h for ten minutes! Head temps at the pre-combustion chambers are equallized and do not see more than a small difference compared to water temp. I have the AAZ thermostat. In the future I think I would recommend the Saab(2.0T 9000) one for the larger opening and softer bypass blocking spring only for working it really hard.

I will mess with this more in the future ... after I get to Newfoundland.

Thanks for all your help and support through this trouble.

[zukgod1]

I have the AAZ thermostat. In the future I think I would recommend the Saab(2.0T 9000) one for the larger opening and softer bypass blocking spring only for working it really hard.

So you have the Saab t stat or the AAZ stat?

What year is that model of Saab produced?

[stopping]

I can't say.... it was my buddy's Saab stat.He just had it lying around so we tried it to see the difference. The real difference in my system now is not the stat, it's the control I have over the opening and cooling temps of the stat. I am running with the AAZ one. but you could do it with any thermostat. I think the Saab would be better because it has a larger opening It opens at exactly the same time as the AAZ and the same travel to the by-pass too. If your able you could swap the by-pass blocking disk so the Saab has the AAZ's larger disk. The Saab's blocks the by-pass fully but it does it by actually entering (slightly) the by-pass before it's completely sealed. Oh and don't use the Saab washer... it raises the stat too much and it will not block the by-pass.... use the volks o-ring.

So just a technical note: Since I am driving everyday, most of the day and I am now geeking out about the cooling of these crazy machines, I have been playing with getting the optimum temperatures. It seems like an orifice, to the expansion tank, just over 3/8" is right to control the stat so the expn. tank temp effects the stat with the most cooling with the least lag time. Disclaimer: under the conditions I am working with.... new rad, AAZ engine, Van and it's weight. I had a 3/8 line before and that proved to be too small. 1/2" is too big (too much diversion of coolant from the rad). My temperatures are being measured from the by-pass while driving and range from 87degC to 94C on a long hill at highway speed.

Oh hey... did you know how much the heater effects the engine temperature and how?

If you are over heating because of this wrong temperature in the expansion tank thing and you use your heater you are sure to see an increase in engine temps while trying to cool it down. The reason is that cool water returning from the heater blows over the thermostat cooling(closing) it causing the engine temperature to go up. I think they did this to get more heat to the heater in the winter. This is a good test too to see if this might be your trouble. If you over heating while your heater is on but not when it's off you might consider increasing the temp in the expansion tank. A few degrees C increase is fine but not if your temps are too high to start with.

Please correct me if this sounds way off base ok? Andrew, Fats, Vince, smog.

[stopping]

Sorry for raising this old post but this is for those folks with overheating AAZ in Vanagons. 

About the coolant system,

In the last post I was experimenting with different sized restrictions to the expansion tank. I took some time to get back to this post but here goes....

While I did have a few issues at the same time and possibly a cracked block I have learned much about the way the system works...... and what it's limitations are.

While opening the flow to the expansion tank will shorten the thermostat response time and  keep the temps low in the first 10-30 min. it is not the best way to cool the engine on the highway. It is not about flow to the rad IMHO is it still the 1-2 degree difference of cooler the water from the expansion tank closing the thermostat.

The best way to get accurate cooling is to reduce the flow to the expansion tank further than the the stock 1.6 restriction. It kind of a no brainer but the best set up is the one in the AAZ cars for the AAZ engine.

I think the expansion tank from the donor engine should be swapped with the engine. The smaller restriction in the matching bottle is the small hose that fills the tank. The fact that the bottle is smaller allows the engine temp to be accuratly controlled sooner.

I am running the AAZ van with the original bottle for now with an approx. 3mm/ 1/8" orifice restriction. Temps are high at first but drop 3-4 deg once the bottle heats up and the engine is cooling nicely.

Just a note: The thermostat mod for AAZ in Vanagons might work but it does not truly address the issue.


 

[jtanguay]

i would also make sure the rad itself is nice and clean... mine had a nest in the middle that really restricted airflow and cooling.  also after using prestone heavy duty flush, i got a lot of brown crap out of my engine.  probably rust and other buildup.  my cooling after that was greatly increased, and so was my cabin heat

[the caveman]

Steve, you made it !! I was bummed when i saw the post but then i noticed the date. Just back from New Brunswick, i kept checking my temp gauge thinking of you but never went past 1/2 even climbing the big hills with my foot to the floor [ boy were those guys on the 3 Hayabusa's mad when they got stuck behind me on the longest hill just before Riviere-du_Loups].

[Luckypabst]

Is this true? I had mine "reversed" (hot in bottom, etc) and quickly boiled my coolant and warped the head on my first hill in the summer desert heat. No issues now with the more conventional coolant flow.

They should be installed according to the Bentley and AGAINST logic.  On the vanagon the COLD coolant hose from the radiator to the water pump should be attached to the TOP of the radiator.  The HOT coolant from the cylinder head should enter the BOTTOM of the radiator.  That is reversed from most cooling systems but is correct for the vanagon.

[stopping]

Thanks for the reminder about rad flow direction. Mine is and always was the flow as marked the Bently.

This is a thread started about this time last year but I wanted to post to this again to continue with the idea of response time of the thermostat to real engine temperature. 

Now that I have a good thermo set up I can read real temps at the engine head so I have been thinking about tapping into the water pump (andrew's idea) and trying the reverse flow through the oil cooler. I have a sensor for oil temps so I could monitor head temp and oil in real time and be able to play with the flow rate of that set up. (not to complicate this thread) I will start I new thread if I get around to starting that experiment.

Andrew, my old block might have been cracked or I might have had a combination of bad IP (Internal P too low), not enough restriction to the expansion tank......
I built a new engine and it is performing famously. I do want to rebuild a pump with a new head now though.

Caveman.... I made with very few problems. And great fuel econmy..... no concrete numbers yet but it only cost about $110 to get to the boat. (1400 k)

Stv