Overheating Investigation, Crud in Coolant System

[Thomas M]

1991 Jetta Diesel, non-turbo; 275,000 miles, original owner

I may as well confess, I have never cleaned the cooling system.
And this may(?) have contributed to the problem.
My heater core exploded due to over heat (I guess) and I have developed a minor fluid leak on the at the front, left corner of the head gasket.
The car runs fine. I won't drive it over a mile. Normal temps at that distance. No smoke, i.e., barely visible. None detectable on acceleration.

A few months ago, I notices that my fill bottle had a lot of this junk in it. It looked like little, 1 mm sized, pieces of cork floating. I sucked it out with my antifreeze tester. I did mean to take the car in and have the system cleaned. I bit too late for that I would say.

Short term goal, get the cooling system up and running.

Here, I only want to present and address the crud that you see in the photos.

What is this stuff?? Am I in for a new radiator??? I installed a new heater core, which I will not hook up until I get the system cleaned. How would you approach this problem.


This picture shows the blown up heater top, looking down into the passages, see the crud. Only a few passages are blocked like this:



Here are some details of what I picked out of the fill bottle and the heater core. Most of the junk in the fill bottle looked like very small grains. Same stuff, though, I think:

[82vdub]

Interesting issue. I'm racking my brain to try to "think" of what would be in a cooling system that would yield results like this. There's the engine block, all cast iron, no issues there. There's hoses, shouldn't have issues there. There's the coolant jug, shouldn't have issues here. There's the fittings etc, shouldn't have issues there. Then there's the radiator and heater core, once again, shouldn't have issue here. I can't think of anything cooling system related that would have parts that would desintegrate like this. The one item that's missing is the product that's put in the cooling system. Was water with a high minearal content used, was a coolant product used that had some "plugs small leaks" type chemical in it, or was there someone along the way (service ship as your the original owner) that put some stop leak into the coolant system? Then, there's the possibility that by virtue of oveheating the coolant, did some chemical gel on you?

At a minimum, I would pull the radiator and use some industrial cleaner and hose and back flush the radiator. You may have all sorts of junk in the radiator that needs to come out. Once that's done, flush the entire coolant system, repull the radiator and clean again, and then run the vehicle for a while and see what this gives for results.

[Prairieview]

I'm guessing the anti-freeze that is in this engine is the anti-freeze that was in it when it left the factory.
Hiring someone to try to clean this radiator is probably as much or more than a new radiator esp. if this guy is not interested in spinning his own wrenches.

[ad]

Pieces of a plastic water pump impellor?

Explains both the overheating condition and the debris.

[Thomas M]

Yeah, I've been bad.......never drained the cooling system. I am the sole owner.

NO additives added by me. I can't speak for what a shop may have done. I've read somewhere (correct me if I am wrong) that VW G12(???) coolant, if mixed with the green stuff, could gum up the works.

Various domiciles, so probably high mineral content water along the way and, for sure, at this house. Say 10 years without and 10 with high minerals.

I've decided to take the car in to a fairly reputable shop where I have done business. Although I replaced the heater core with little trouble, I don't want to get in over my head pulling the steering pump, water pump and who knows what else if things don't go right.
I've get to get this car back in to service asap.

Step one: clean up the cooling system. I've spent so little money on this car over the past 22 years that I am willing to bite the bullet and get things right. New radiator, thermostat, water, pump, hoses??(all current hoses original except for one), fluids......none of these items are out of the question.

Getting the system thoroughly cleaned out takes some trust on my part. Do they have the patience to listen???

Although I try to take good care of the beast (all 52 hp; I love this car) I can say that this mess has resulted from neglect. That's why I am willing to spend the bucks to fix things right.

As I said, this is only one part of the damage that surfaced with the overheating. The head gasket, which has only leaked the nominal amount of oil, is leaking antifreeze at the corner just to the rear of the vacuum pump.

I'll get to this in another posting, except to say that now all gauges and lights working(praying to crows seemed to help as all else failed), starts right up, no smoke on start or acceleration, comes up to temp(4th bar on gauge) after 4 miles of driving; just that nagging little leak at the gasket.

PS: just noticed, when hot, a slight hissing, bubbling leak at the 2-hose flange on the cylinder head. Very tiny leak. Could this be seeping over to the gasket???????
Also, no dripping on the pavement after driving.

Thanks for the info,

Thomas

[82vdub]

One other item that should also be investigated is that you have coolant flowing out the small hose into the overflow jug. This is crucial for proper removal of air from the system. There's a small orifice in this line, close to the coolant jug. If it's still in the line, it's probably plugged. You need to remove the oriface and make sure coolant flows into the overflow jug. If you don't, then the air must "burp" out through the bottom hose into the jug, and this will result in higher engine operating temps, or even possibly overheating.

As for the coolant leak at the head, you'll need to decipher whether it's coming from the head gasket or elsewhere. Nobody can determine that through a forum. You may have warped the head a bit, and the head gasket could go as a result from this, or it may not. I've had the antifreeze leak at the corner of the head before, and just let it go. You could always do a retorque of the head bolts to make sure those are snug.

[Thomas M]

Thanks again, 82vdub !!

That hose you mention, from the top radiator hose to the fill bottle seems to be plugged. I pulled it off, engine cold, of course, and tried to blow or suck from it. I could not get any air to move either direction.

I put my tongue on the open end of the hose and squeezed the upper radiator hose and could feel no pressure change, like it is plugged.

Also, I can press it flat with my thumb until I get to withing about 8 inches from the bottle to where it starts to feel almost solid. Feels plugged up to me, although I do not know where the orifice might be. There does seem to be and especially hard spot near the bottle.

I might mention that observing the level in the fill bottle as the engine cooled led me to think that air might be getting trapped. This was before you mentioned the above situation.

Are these tests valid to confirm what you suspect is going on?????

Thomas

[82vdub]

The orifice is about 8" from the end of the hose, if I remember correctly. It's hard plastic, so it's not compressible at all. Cut that upper small hose short and remove the orifice from the line, and any debris before connecting it to the overflow jug.

You can probably save yourself some repair work if you just remove the radiator and flush very well, reinstall and then flush the coolant system, then flush the radiator again. If you really want to do it, go get a $100 radiator, flush the old system first then install the new radiator and hoses etc and you may be good to go. The coolant age may have been the issue, and no other parts were failing. At least that's what I'm thinking. 23 year old coolant? You're probably lucky you didn't freeze the block with this nasty of a winter we've had here in the US.

[surfcam]

While you have the coolent out I would check the top plastic flange on the head for cranks (real crap compared to the old aluminum ones, conversion is possible). If you take the o-ring out and look very carefully you might find a crack near the bottom stud hole in the flange. I've had this happen more than once. The last time it happen I lost a sale on my 89 Jetta. I told him it's probably a hose leaking but insisted it was the head. So I said bring her back. Real nice guy sold me it back for $100 less for my trouble he said. I never said a thing. Then I thought maybe I can sell it 25 time and make 2500 ah ah. Not. Then two weeks later two Mexican Menanites show-up and just about clean me out. They bought my not running 91 Jetta, running 89 Jetta, dead engine and four snow tires. yippy. Wifey says I can buy more now. Wagon's, Eurovan's and Golf's is what I want.

[Thomas M]

Surfcam,

Your message is validating. I've gotten a little hopeful that I may NOT have warped my head.

This is what I interpreted as a sign of a warped head. No other water leaks detected after inspection with flashlight and crawling under the car and looking at the back side.....just some light oil seep. You see that it is right behind and below the 2-hose flange on the head. The water could be seeping from the flange and slithering around the gasket in the air flow. I hope so.



I took the car out around the block, now that I can monitor temp on the gauge, and got it pretty hot.
Pop the hood. I could smell hot water/coolant. Something was making a hissing noise....But here's the clincher: I jiggled the radiator hose attached to the flange and I got a little, tiny spritz of hot water and steam leaking from around the flange !!!

I hope that is the extent of my "warped head" fear and that the engine is ok. Gasket and flange will be replaced......maybe the one on the side of the head too.

Your reply was quite on the spot.

[82vdub]

So what have you done to address possible cooling system issues, or are you still on the theme of bringing it somewhere. Do you have coolant coming out of the small hose into the coolant jug?

It's not 100% foolproof, but a really easy to test to see if you likely have a cracked block/head or bad head gasket is to let the car sit for 8 hours or overnight. Start it up, and if you've got pressure in the coolant jug, combustion gasses are getting into the cooling system.

[Thomas M]

82vdub,

The car is in the shop for new T-stat, water pump, hoses, radiator, antifreeze.

Oh, and a flush, I stressed that I wanted it cleaned out really well......."Yeah", Tom said, "I overheard you
talking to Debbie"!!! I think he got the point.

So, I don't have it at home to run the test, but will do so when I get it back.

[82vdub]

Hopefully the shop finds out if the head gasket/block/head is or isn't bad before you just have them fix it then have to kind of start over. Maybe have them check for combustion gas going into the coolant system before they just change parts. Maybe you've got them on that track...........

[Thomas M]

82vdub,

They are going to only renew the cooling system components at this time.
I'll drive it around the shop for a while, return to the shop and take a look at the engine.

The two-hose flange on the front of the cylinder head may have a leak.

If the engine is cool and coolant pressure has diminished, I could try your simple test and
check for pressure build up in the overflow bottle.

If anything suspicious, I'll leave it.

The next thing would be to think about looking at the cylinder head, block, gasket, etc.
I was about 10k miles from a belt change, so I would have them do that at the same time.

They are very busy as 2 other VW shops in the area have recently gone out of business.
I doubt they have gotten to my car yet so I will drop in on Monday and talk with Tom.
I told him earlier that this is just stage one and that are more issues which have to be addressed.

I am not adverse to leaving it there to continue what needs to be done.

[Thomas M]

Just a reminder....I am the originator of this threaed.......

The car is back from the shop. All new radiator, hoses, water pump, t-stat, heater core (installed, not hooked up yet), v-belts, side and front head hose flanges, pressure cap. I purchased a new fill bottle to install myself. It's in the parts bin for use at a later date.

I did a quick cold pressure test to see if any combustion gas might be leaking into the coolant. I used a rubber glove over the fill bottle neck and it remained limp, no gas pressure detected. I'm going to check it with the U-View Gas Tester when I get one. Which I did. I'll skip the details which I will post under separate heading. The results were negative for combustion gas leak. This confirmed what the shop tech told me.

Apparently there was no head damage, at least at this assessment. The new flanges stopped the leak that I though might be the head gasket. Good and dry now. The drive home was uneventful although the temp gauge acted flaky. It didn't register what I expected (only about one bar off the low point while driving on the freeway. Then it dropped way low .....??? Of course, that made me a little anxious. But on arrival at my place the engine seemed fine, the hoses were not extremely hot to the touch and everything looked A-OK.

I replaced the voltage stabilizer which supplies working voltage of 10 volts for the gages and, I'm guessing, the idiot lights. All gauges and lights, except the glow plug light, working normally. I'll cover some details in another posting.

Now for some revealing photos.......of the prime suspect in this adventure, the small diameter hose that runs from the top radiator hose to near the top of the fill bottle. Yes, it was plugged and was probably the cause of the overheat/heater box disaster.

Here is the hose, sliced and diced. Right thumb near the orifice in the hose and left thumb near 23 years of sludge buildup!!!!! Wow!! and more down the tube, I suspect. This shows what so many have written about in this thread and what I felt as hard lumps down the hose.



Here is one view of the orifice which was about and 1 1/2 inches from the fill bottle:


Another. Notice the crud. It could plug the small hole by itself if it wasn't for the pressure:


It makes me wonder why they have that orifice in there at all????? Maybe there would just be too much flow into the bottle.
And, as you all have pointed out, that little hose now just gushes fluid even at low idle.....nice and juicy. It makes a good "canary in the coal mine" for the presence of coolant crud. I intend to keep it clean.

Thanks for all of the tips.