Coolant Over Pressure Issue, Head Gasket, Therm, ...???

I have a 2001 Jetta TDI ALH that is having major over pressurization of the cooling system. I have replaced the water pump with a metal impeller style water pump as well as the thermostat about 30k miles ago. I had also changed out the head gasket at that time as well. The reason being that the previous owner couldn't keep oil in the engine and spun a rod bearing and bent the crank but that's another story. The block had been replaced at that time as well. Back to the issue at hand. I can't keep coolant in the engine long at all. I can drive maybe 10 miles up the road and then I have a puddle of coolant under my expansion tank and on the ground. About 2 months ago, I hooked up a garden hose and ran it through my system to see if I had any blockage and it seemed to flow well. At that time, my car still produced heat through the heater vents and I could get many miles without filling up the coolant. As I stated earlier, I can only get about 10 miles or so before it overpressurizes and blows the expansion tank. I do not have any heat coming from the vents at all at this point. I was thinking possibly the head gasket was allowing gases in to the coolant causing the overpressurization but now I'm not sure. I have the gasket in hand and was ready to tackle the head gasket this weekend but I do not want to jump in to that and it not be the issue. What are your thoughts? Possible blockage somewhere like the radiator or heater core or even the head? Is it likely to have a bad water pump with the updated metal impeller? Bad thermostat? Any thoughts or suggestions are very welcomed. Thank you all in advance

Also, if there is any kind of load on the engine at all, forget about it. The system pressurizes immediately. I drove through West Virginia this summer and had to continuously pull off the side of the road due to the temp gauge climbing quickly. I always managed to pull over before the temp gauge pegged but the fans have come on several times. Thanks

The over pressurization of the system under boost is most commonly head gasket issues. The no heat from the vents is more likely a plugged heater core. Perhaps some previous owner tried a stop leak in a bottle to try to cure the problem you are experiencing.

Sound like the head is coming off, but I would be checking for how flat it is before slapping it back on again, especially if the engine has over-heated. Try and determine where the breech is when it's apart.

When the heater hoses are disconnected, try running water from a hose through the core backwards and forwards to see how it is flowing. I would replace the thermostat too.

compression test may be in order

I have had the car for about 30k miles and the heater was always cooking. I do not have any leak from the heater core itself. The only discharge comes out of the expansion tank. I have no loss of power at all from the engine. It runs like a top other than the pressure. I will run water back and forth through the heater core this afternoon. So you don't think it could just be a circulation issue?

The no heat issue could be related to heater controls too you know. If you can circulate water through the core and the radiator, then with you nice new water pump, circulation should not be an issue.

Unless there is a blockage somewhere, which is what I'm thinking (hoping).

Any suggestions on how to approach this?

maxmoo said:

compression test may be in order

Click to expand...

....

You know it's a headgasket issue

You are hoping it is not. Pressurize the cylinders and watch for bubbles in the coolant tank

Dimitri16V said:

You know it's a headgasket issue

Click to expand...

And the head must be resurfaced. It probably was not done 30k ago and may have been a problem since, now to a point the car is not drivable. In order to resurface the head the valves must be removed, best to rebuild the head or have it rebuilt. Head bolts are stretch bolts, must be replaced.

Forget the blockage issue, unless the PO and you have been running straight water causing tons of rust. Otherwise, I cannot imagine what would cause a blockage.

Is the coolant (hopefully the right stuff) nice and pink/orange, or, is it dark? If it is dark, combustion gasses most likely getting into the system via a blown head gasket.

Was the water pump absolutely for an ALH engine? There is a minor difference in pumps for the gasser engine vs the diesel engine. Did you use a quality brand T-stat?

The one real mystery in your comments is that you say there is no heat now. Have you felt of the two hoses going thru the firewall to the heater core to see if they are warm/hot?

Can you tell if coolant is circulating by watching the inside of the coolant expansion tank with the lid off?

I did have a higher concentration of water in the system throughout the summer because the car would constantly need it added. Now that the winter has decided to show up early, I have been using 50/50 mix using g13 coolant but I can't afford to keep putting coolant in it every 10 miles. I am not completely convinced it isn't a blocking issue as of yet. When the car is at full operating temperature, the upper radiator hose is warm but the lower radiator hose is almost ice cold.
I believe that the non heating issue is related to the lack of coolant in the system at the given time? The water pump was definitely for an ALh motor and came from a reputable source. The t-stat came as a part of the timing belt kit as well an was a good brand t-stat.
It is hard to judge if there is any discoloration of the coolant because it doesn't stay in the system long enough. When the engine is running with the cap off of the expansion tank, I pulled the hose off the tank and watched as the coolant came out of the hose. The flow isn't that great at all and there also seemed to be small air pockets.

Classic head gasket failure.

I agree with VeeDubTDI.

For informational purposes: The ALH engine will purge air from the system in short order. I've never had an issue with "filling up" the cooling system after a TB change, etc. So, thinking there is an air lock is highly unlikely under normal circumstances. .... since you are having to add coolant, obviously there is some air moving thru the system.....every 10 miles (not normal circumstances).

The coolant flow thru the small hose to the expansion tank is slow at idle.

The top rad hose that enters below the IP is the return hose from the rad (actually comes off the bottom of the Rad) .......... unless it is a hot day in July, etc., that hose will seldom be HOT. In fact, on a cold day, the T-stat may open just a smidge but that hose will still not get hot as the coolant from the rad out front is cold......

Flow of coolant

Excluding the Rad out front, there are three routes coolant flows: 1. from the coolant flange on the end of the head, it flows into the EGR system and Heater core (summer or winter) then back to a long black steel pipe parallel to the block below the IP which terminates at the housing on the block containing the T-stat and water pump. 2. The small pipe from the end of the head Ts to the small pipe coming out of the EGR cooling system then returns to the coolant expansion tank then from there it flows to the long black steel pipe via a T close to the Dip Stick tube, and 3. Off the coolant flange a hose takes coolant to the oil filter housing for cooling the oil. It returns to the long black steel pipe via another T. Those three loops of coolant are always in motion if the engine is running.

The returning coolant via the long black steel pipe eventually gets hot enough to cause the T-stat to open and blend some cool coolant from the Rad out front. Only during extremely hot days does the T-stat fully open!

(A dead T-stat generally defaults OPEN which explains why the engine fails to warm-up on cold days.)

There you have it!

You probably need to do a compression check ... The longer you drive it the greater the possibility of damage to the engine....over heating, coolant can destroy rings, coolant can destroy cylinder walls, gases between cylinders can erode the head and/or block surfaces, etc.

Thank you everyone for your words of wisdom. I spoke with a shop yesterday on the phone that could get my head in for resurfacing this week. I am going to remove the head tonight and possibly rent a car for the next couple days. This TDI is my only means of transportation and I have been driving it back and forth to school (~30 miles round trip) every day. Hopefully the shop can get it back to me in a timely manner. Do you think I will have to go to the next thicker size of head gasket?

First. Make sure the shop understands that if the head needs to be milled to make it flat, that the stack height of the valves needs to be adjust back to match. You can't just mill the head surface without matching the original valve seats relationship to the head surface.

The head gasket thickness is another matter entirely, and has nothing to do with whether the head has been milled. You could cross your fingers and just use the same thickness head gasket, but the way to do it correctly is to measure piston protrusion above the block deck. This measurement will dictate the thickness of the correct gasket.

Are you planning to pull the head youself, or will you farm the job out?

They are a very good shop and will do a great job I'm sure. I have all three head gasket sizes on hand so that I can be sure I have the right one. I will measure the piston protusion. Thanks

About four years ago (long story short), I helped a guy that had the head milled beyond spec. (Hint, key words: long story short).

So, we ended up cutting valve seats, cut valves a very small amount and then shaved off the ends of the valve stems........... I do not recall the head gasket thickness, but I'm guessing we went with the thickest.

Today, over 4 years later and about 75k miles that engine is still running just fine!

Make sure the block surface is cleaned up good. The surface of the head must be milled slick ......... no grooves, otherwise the gasket will leak (part of the long story above).

EDIT: Point is, there is room for error! My guess is: the head is probably no more than about 0.006" off straight, if that is the problem. On the old 1.6 and 1.5 IDI VW diesel engines, spec is 0.004 off straight. Keep in mind, your head may not need resurfacing.... just clean up and a new gasket, bolts, etc. The shop should have a straight edge to measure straightness and should know how to do it!

Thanks Andy. I have never had a head resurfaced before. I would imagine I have to tear down the head for this to be done?

You would remove the camshaft, injectors and the glow plugs before dropping off the head at the shop. Put the cam caps back on their saddles in their original positions. If you are experienced enough to evaluate the condition of the cam fine, but if not, take it to the shop for evaluation.They will do the rest.

You sound like you have a shop you like, but allow me to recommend a shop in MO (Franks TDI). Frank Irving uses Franko6 as a handle on this forum. TDI's are all he does, and he knows the idiosyncrasies of these engines well. You would contact him, and Frank will tell how to package the head up and send it to him. He will provide a shipping label so it's easy.

Thanks Yblocker. I knew that I would have to remove the cam, glow plugs and injectors. I wasn't sure about the valves. I've heard so many good things about Frank but this being my only means of transportation. I need the turn around time to be a day max and my shop said they can do that. I appreciate the help as well. I'll probably start the disassembly in a couple hours after I finish a physics lab report. Gotta love juggling school, work, and now the tdi.

Well the head is removed but the number 4 glow plug seized up and broke spinning the hex around the electrode. The threads are still fine down below and is like to try to avoid drilling the oul out and inserting a helacoil. Any suggestions on how to get the broken plug out? Thanks

You are bringing the head to a machine shop anyway right?
Let them deal with it.

I took it there this morning and dropped it off that way. I was just curious for future knowledge.

Kurt13rager said:

Well the head is removed but the number 4 glow plug seized up and broke spinning the hex around the electrode. The threads are still fine down below and is like to try to avoid drilling the oul out and inserting a helacoil. Any suggestions on how to get the broken plug out? Thanks

Click to expand...

The trick with removing glowplugs is that the maximum removal torque is 25 ft-lb. Set your torque wrench to 25 and try to loosen the plug. If it doesn't break loose, apply penetrating oil, heat and repeat. Exceeding 25 ft-lb almost guarantees a snapped-off plug.

Thanks for the tip RacerTodd. I will keep that in mind for the future.