Coolant issue, maybe?

[Jettagli16v]

Good afternoon, GTD!
Long time, no talk!
(damn Diesel has been jut running like a top...!)

Now I have a curious one....
I'll try to give all the relevant data I have, and see what you guys think.

Car: 85 Jetta TD, rebuilt engine last year, MLS HG & ARP studs, EGT pre-turbine (Aircraft spruce / VDO),
Radiator less than a year old, all new hoses at the same time..

-Started my car after work, went to a gas station, and let her idle for like 5 minutes while I went inside.
When I came back out, found a puddle of coolant under the car, coming out of the cap.
(Reservoir full to the top, and it was not overfilled before).
Drove it home, pissing coolant the whole way.
Temp gauge went over the LED within 10 minutes, and was pegged on top, with the red LED flashing within 20.
(At this time, I am getting really nervous, but I kept checking my EGT, thinking it cannot be overheating too bad with EGT ~ 450, so kept driving)
When I got home, I left her running, and got out to inspect, and found:
Coolant still coming out of the cap, upper and lower Rad hoses very warm, fan not running (temp still at the top of gauge) and the driver's side of the radiator is appreciably cooler than passengers side...

Diagnosis: T-stat stuck, hose collapsed (not likely as they are all new), clogged radiator (again, < 1 yr old), or combustion pressure getting into water system...

Repairs:
Replaced T-stat as I have never looked at it.
Re-filled with G12, and started it to check. Within 5 minutes at idle, temp is 75% and climbing... Shut her off. Not a bad T-stat.. (also tested the old one I pulled out, and it tested fine)
(After the fact, my VW tech friend asked me if I fingered the impeller on the water pump while I was there.... I did not)

Checked head stud torque: warmed the engine up, checked at 110 lb/ft, got maybe a 1/16 to 1/8 turn out of two studs, and then checked again at 115 lb/ft, no movement. Started the car up again to test this theory, same results (boiling in 10 mins or so)..

Then, one of my other VW friends says check the overflow into the bottle to see if the h2o pump is moving water.
No coolant pissing into the top of the bottle..
I felt the overflow hose (from the upper rad hose to coolant overflow bottle) and it has great pressure behind the nylon reducer, but no pressure after.
Cut the hose off, pulled out the nylon reducer, and found it completely blocked (very tiny hole: 0.5 mm?).
I removed it, re-attached the hose, and VIOLA! (good flow now pissing into the overflow bottle) BUT,  Now the car will not really even warm up to temp!!

Feeling confident I was on the right track, I went for a drive, and after 20 mins of beating on it, was unable to get the temp past say 25% on the gauge (very cool), but rad hoses are reasonably hot to the touch, rad fan cycling, and both sides of the rad are now hot...
After a day of driving, I found the car to run almost too cool.
It never gets into the normal range (indicator covering the LED in the gauge), always stays cool.
And now, if I get her warm, and let her idle for 10 mins, it will begin to lose temp on the gauge, where it used to maintain temp in the "normal" range until you shut the car off...

SO, I thought I had it all figured out, I will make the hole in the nylon reducer a tad larger, to decrease the likelyhood of future obstruction, and get her back up to temp..

Drilled a 1/32" hole in the nylon reducer, installed it, and it has made almost no difference:
Temp gauge will hardly go past 25%, unless you are mean to her..


So, the question is:
Could that stupid little reducer make all the difference in the world for cooling,
could it being stopped actually keep water from moving across the radiator for cooling?
Could enlarging the hole just a little keep the car from getting up to temp at all?
(Or, am I still looking for an intermittent issue, and this was irrelevant...)

I had always heard, just take that thing out and you will run cooler,
but if it is as severe as this, that would not be good advice..


Thanks in advance!
-Brad

[R.O.R-2.0]

running with the needle covering the LED is a little warm for my tastes.. usually 25-35% on the gauge is perfect.

[Jettagli16v]

Hmm,
If this is in fact a universal truth,
I suppose I would be fine with it.

But, since I have had the car,
It warms up to the bottom of the LED,
and then will float from the bottom to the top of the LED,
occasionally going a little over the top if I keep the EGT up at 1000 for a while..

Maybe I am worried about nothing?

-Brad

[Powered by Spearco]

The clogged restricktion could be sediment from the heater core or the radiator. The fan swt. and thermostat should be matched for proper cooling.

Sounds like your radiator is partially clogged and is what is causing the over heating issue. Its weird how all of a sudden it happened, but can happen.

If the water pump impeller gave way and is free spining, that could also cause the rappid over heating too.
But you said its flowing back to the bottle well now after removing the clogged restricktion.

Hmm?

[R.O.R-2.0]

he has no cooling problems now. just thinks it runs too cool..

but it was probably just ALWAYS running too hot..

[Jettagli16v]

Thanks for the reply, Powered by Spearco!

The coolant system has been a bit troubled for most of the time I have had it,
I have been unable to remove an orange colored gook from the inside of everything,
despite doing 2 thorough rad flushes,
and using nothing but VW G12 & Distilled since I have had her.

Clogged rad is still on the table,
but it certainly got worse and now better,
(I could see a clog only getting worse, but could it get better in time?)
and the rad is less than a year old.
(Flushed 2x with a rad flush product, and then ran garden hose through everything for like 20-30 mins, before replacing it)

Good flow through the overflow hose,
so I am thinking not a spun impeller, unless it is totally intermittent.

The weird thing is that it went from normal, to overheating, to too cool, and the only thing that made any difference is the small nylon reducer!  (New > Clogged > removed > drilled out)

R.O.R-2.0 - quite possible,
but what I know of the VAG family is they always set up cooling systems to be in the dead nuts middle of the gauge.
The mk4 chassis has a 30 degree temp swing before the coolant temp gauge moves a mm in either direction.
They do that so drivers always look down and see happy info, unless things are really screwed.
I still don't believe in my heart that they sent these out from the factory running 25-35% on the coolant temp gauge.

BTW, who is running the nylon reducer in their overflow hose?
R.O.R - do you have one?
I think it may be that w/o the reducer, we will run 25-35%, and with it will keep it in the middle?
Is that the function of the reducer, to account for the inherent temp differences in gas vs diesel?

As always,
Thanks!
-Brad

[R.O.R-2.0]

none of my cars have a reducer..

all of my cars run below the half way mark, every single VW ive ever owned with a good cooling system atleast.

my 85 golf used to run a little past half way, then i replaced the radiator and flushed the system and it ran below the half mark like the rest.

like i say, all my VWs, and most other VWs that other people own, have all ran right around the same place on the gauge.

i always started to worry when any of my cars got up to half way on the gauge and wouldnt come back down..

[Jettagli16v]

Hmm,
seems like we could effectively correlate the reducer with the mid range temp average then?

And, at the end of the day,
if a plugged reducer makes temps skyrocket, and no reducer makes it almost never leave the block at the bottom,
I should probably rest easy with a 1/32" hole, and cool temps, good flow,
and both sides of the rad equally warm.

-Brad

[R.O.R-2.0]

i really dont think the restrictor matters.

it just allows air to leave the system, and the coolant in the expansion tank to circulate..

one of my cars didnt even have an expansion tank.. it still ran below the half way mark on the gauge..
and because it didnt have an expansion tank, it didnt have the return line, or restrictor..

radiators can have cloggs and still flow great. but flowing great, and being able to cool great are 2 different things..

what if all the coolant in your system is just going thru like 5 or 6 tubes in the radiator? instead of all the cooling tubes?

its still going to flow fine, but wont have nearly the cooling capacity it should.

being that you said your cooling system was way dirty at one point, im gonna say that your radiator is still plugged.

[Jettagli16v]

Thanks, R.O.R.
While I am still keeping that on the table as a possibility,
the curious thing is how suddenly this happened.
(went from perfect, to boiling over rapidly and consistently)
and the fact the removing the reducer alone caused the temp gauge after 10 mins of idling to go from
90% to 20%....
Radiator clogging / loss of good flow should be slow and progressive, correct?
(assuming no trauma to the coolant system, like throwing in a qt of permatex)

Also, I am always gunshy of the theory that VW (or any of the Germans, for that matter)
do things that are completely unnecessary.
Every time I thought I could better engineer a VW, it did not work out well for me.
Seems as if the Krauts have their stuff together after all, and unnecessary components are not generally their style.

-Brad

[R.O.R-2.0]

Thanks, R.O.R.
While I am still keeping that on the table as a possibility,
the curious thing is how suddenly this happened.
(went from perfect, to boiling over rapidly and consistently)
and the fact the removing the reducer alone caused the temp gauge after 10 mins of idling to go from
90% to 20%....
Radiator clogging / loss of good flow should be slow and progressive, correct?
(assuming no trauma to the coolant system, like throwing in a qt of permatex)

Also, I am always gunshy of the theory that VW (or any of the Germans, for that matter)
do things that are completely unnecessary.
Every time I thought I could better engineer a VW, it did not work out well for me.
Seems as if the Krauts have their stuff together after all, and unnecessary components are not generally their style.

-Brad

well, when the return line gets clogged, air can not escape the system. that small return line is where 99% of the air trapped in a cooling system escapes from.. clogged line = over heating car.

and when the whole top of your cooling system is full of air, it can not cool. thats why it puked all the coolant, and then it was fixed when the return line could actually function again.

drain all the coolant in your engine and fire it up if you dont believe me, i bet it warms up about as fast as when you had a clogged return line.

the head, top of the radiator, rad hose, and heater core were probably all filled with water.

you can hypothesize all you want, but ive dealt with a fair amount of VWs with this exact problem. and a clogged return line is the culprit 90% of the time.

and your radiator is still  partially clogged i bet. that flush-in-a-bottle hardly works.. only if you got mixing of fluids (like oil in your coolant) its basically just some semi-powerful soap. simple green would prolly work better..

[DCC]

like i say, all my VWs, and most other VWs that other people own, have all ran right around the same place on the gauge.

Just for the record: Every VW I've seen or driven around here (including my previous mk2 GTi and my current mk2 GTD) have had the temperature gauge in the middle when driven. Every one of them. Doing some tests with an infrared thermometer showed that's the case when the water temperature is around 80ºC.

[R.O.R-2.0]

weird..

cause all mine run below the half way mark. mk1s and mk2s.

my GTI would get to the top of the white area, about 25% on the gauge..

sitting in a drive thru would bring it up to half way, and kick the fan on.

same scenario with my diesel rabbit, it runs at about 3/8 on the gauge. usually right around the 4th tick mark on the gauge.

my gas jetta, same deal. half way between the white mark at the bottom, and the red light. again, maybe 3/8 on the gauge.

maybe i have just solely owned cold blooded VWs..

[DCC]

my GTI would get to the top of the white area, about 25% on the gauge..
same scenario with my diesel rabbit, it runs at about 3/8 on the gauge. usually right around the 4th tick mark on the gauge.
maybe i have just solely owned cold blooded VWs..

Not that weird. I don't think your cars worked that cold. Let me put it in perspective:



It's the typical mk2 cluster. I was told somewhere (I think it was the guy working at spare parts in our local VW stealership), that the gauge tops at 110ºC.
In my owner's manual it tells you to wait for the first line before "accelerating hard and putting the engine into stress". That makes me believe that the first line can't be that far away from the operating temperature. On the mk3s the gauge says "70-110", and it works exactly like mk2s, so they can't be that different.

[TITan]

As far as I know the LED is at 90°c (the position on the scale... NOT that it comes on at 90°c), so it probably is the same as the mk3.

Now I come from gas engines, but 90°c is probably the ideal temperature for the engine as far as eficiency and lubrication vs. risking running it too hot when the load increeses.