92 EcoDiesel boils over

[Garfield]

I have a 92 EcoDiesel with a boil over problem. Have had this problem from the day I bought it. 
The temp gauge gets to about the 1/4 mark, then coolant boils out of the expansion tank.
I have changed the water pump, t-stat, had the rad flushed, replaced the head gasket/bolts.
The temp gauge gets to about 1/4 mark, this is just before the t-stat opens, then boils over.
The upper rad hose was patched together when I got it, but I did not think this would cause it to boil over.
When you rev the engine, there is a steady stream of coolant coming out of the little hose going to the expansion tank.
When idling it kind of comes in spurts.  Any thoughts would be a great help..
Bought this thing a year ago and have put a massive 4 miles on it..

[theman53]

I don't know for sure, but it sounds like a water pump, but you put one of those in. I would take the T stat out and drill a small hole in it say 3/32 or 1/16 so it for sure can't trap any air. While you have the t stat out make sure it opens by putting it in water on the stove. Watch a thermometer to see when it opens so you know that it isn't 230 or something. At worse case if the upper rad hose was pinched and the previous owner ran it like that maybe the head gasket could have went and then you will start another thread, but try what I have suggested if you have time to.

[Garfield]

Drilled the small hole in the t-stat.
Checked the t-stat, it opens around 195 and full open at around 212.
Upper rad hose is not kinked but runs over the top of the alt bracket.
Looks like the point where the rad hose runs over the alt bracket is the high
point. Have replaced the head gasket and bolts. Sill boils over at the 1/4 mark on the temp gauge.
Had head shaved as it warped a bit, (also had detected exhaust gas in the coolant).
Did not have the head pressure tested, thought the warp in the head caused it to boil over.
Thought the rad was blocked, but it boils over just before the t-stat opens. If the temp gauge was
around mid point and this started, I would suspect the t-stat and rad.
Question.. while the car is idling, is the stream coming out of the small hose suppose to be a constant
stream or come in spurts??

[Rabbit on Roids]

constant stream on all the ones ive ever messed around with. sounds like your gauge is either goofy, your sender is goofy, or your head has been doing crack. take the wire off the temp sender and touch it to a grounded object (ie bellhousing since its close) the reading on the gauge should be MAXED OUT. also, if you can afford it, install a real temperature gauge that reads in degrees instead of the stock VW gauge. i hate stock temp gauges, i will never trust them again. But honestly, i think its time to pull your head again and pressure test it or something. every time i get bubbles in the return to the over flow tank, ive had to replace the HG shortly after seeing the bubbles. you might get lucky and not need a head, but we will see...

[Garfield]

Thanks for the reply Rabbit.. I am going to try removing thee t-stat to see how long it takes for it to boil over..I am guessing that head may have a crack in it like you suggest. Will plan on a new head but hope that it is something else. Not sure what..Have not done a compression check as the bores looked good during the first HG replacement.

[Rabbit on Roids]

its also possible (hope like hell) that its just a head gasket... ive heard of brand new head gaskets failing right out of the box before.

[theman53]

I wouldn't run it with no t stat. I have done that and they usually boil over faster. Not idling, but running down the road. I think it is because the water isn't in the engine long enough to pull the heat out so as soon as you run down the road it is fine. Then you come to a stop or idle and it heats the water real quick and it will boil...at least that has been my experience and with more than just the VWs. The way you said it isn't a constant stream leads me to think the water pump. That is the only way I know when mine go bad for sure. All of the new ones I put on always have a stream even at idle.

I hope for you it isn't the head.

[Garfield]

Theman53.. Thanks for the warning about the t-stat. Will try another water pump first before condemning the head gasket. Could there be a blockage in a hose? I looked for blockage when I was replacing the water pump the first time did not see any, but then I was not looking specifically looking for a blockage