ALH Engine overheating except with heater on

[karlaudi]

I have a 2002 Golf GLS TDI (ALH). Always dealer serviced since new and almost always within a few hundred miles or less of recommended intervals.

About a week ago, on the eve of it's 160k service, my wife and oldest daughter noticed it starting to overheat during a typical SF Bay Area commute. Resourceful, my daughter accessed the internet via her iPhone and quickly deduced to run the heater on full and the engine never got above three-quarters on the temperature gauge, according to them. As long as the heater is on the engine operates at normal temperature; performance is normal. It has been this way for a week.

My dealer has had it for two days. Initially they confirmed a failed radiator fan thermo-switch. Now they are saying, after conferring with VOA, that though there is coolant flow through the radiator and the system is not being pressurized by exhaust gases and there is no evidence of coolant in the oil or oil in the coolant, the head gasket is blown and maybe the head is warped because the upper radiator hose is hot and hard and the lower radiator hose is cool and soft.

Any comments or experience to share?

Note: Water pump was replaced at 80k during the timing belt change, but I need to check my records on a thermostat.

Thanks for any and all input and suggestions.

 

[Ski in NC]

With engine idling, verify the plastic coolant bottle has a dribble of coolant entering from the little hose near the top.

Also, how strong was the cabin heat? Good hot heat coming from the vents, or semi-lame weak heat?

 

[karlaudi]

Good hot heat.

 

[Ski in NC]

Check for bottle dribble, but that is probably ok based on "good hot heat".

Probably next thing would be to swap the thermostat. Not likely for tstat to fail closed and cause heating, but it could happen and is not expensive to change.

 

[karlaudi]

Thanks Ski, My thinking too, but.... the dealer thinks they need to pull the head. They put all the old parts back on the car, so no working fan either. I am off to get the car. Will keep this thread updated as to the results.

Thanks again!

 

[saturnhacker]

Run the engine from cold with the overflow cap off and see if the coolant wants to push out of the bottle. A blown head gasket pressurizing the cooling system will normally force the coolant out, if its a bad leak it will happen fast and forcefully, a smaller leak might only evidence itself after some driving and at higher speed. There is a chemical test that can be done to detect combustion gas in the cooling system. Couple other things to look for, bad pump withsh loose/cracked impelled, thermostat stuck shut. Absolutely don't pull the head without pulling the thermostat first.

 

[saturnhacker]

Recently had a b4 similar deal, owner driving around blasting the heat to keep it from overheating, new stat and everything good

 

[karlaudi]

Well, the car slogged home in San Francisco to East Bay stop and go Friday commute traffic after we pick it up from the dealer. I escorted my wife most of the way with our 2012 Golf TDi. It took about an hour to drive about 15 miles. My Wife driving with the heater and A/C on. My wife called to say the car ran cooler with the heater and A/C on than when we brought it in with the heater and A/C on, before she stopped by a local store prior to coming home. Coolant level very low, it should be noted, after the dealer tested it. More about this later.

[saturnhacker, thanks for the tips. I have a college degree in automotive technology and I'm graduate of BMW NA's first ever class of their STEP program. I am no longer in the trade and have no time to service my own cars. I am aware of the chemical test you refer too. It has been around since I was in college (for cars) in the early mid-1980s, as I recall.]

The dealer confirms that there is no "classic evidence" of a blown head gasket, though the car will eventually overheat at idle with no fans running. They believe all related and associated relays and sensors are correctly preforming to specifications. The car refused to overheat (ten minutes at idle) in my driveway after it returned home this evening, after a brief stop at the aforementioned grocery store near the end of the commute.

More a little later....

 

[saturnhacker]

So does the cooling fan come on? Running the a/c should activate the fans but also increases the heat load on the radiator somewhat although obviously its not very warm where you are right now. As far as the dealers description of your hoses, normally the upper (inlet) hose is warmer than the lower (outlet) hose but more extreme temperature variation shows lack of flow through radiator. The very first thing I would do is replace stat, if that doesn't fix it I would investigate a bad pump. The plastic impeller pumps would have erratic operation due to a cracked impeller. Problem usually seen at higher rpm, less at idle. How quickly did the car appear to overheating when you picked it up? When the pump was last done do you know if the replacement was metal or plastic? If you know the pump impeller was metal you can probably rule it out for failure.

 

[migbro]

Unbelievable. But typical dealer malarkey. Let's just take the head off for....no reason.

Have you ever had a fuel leak from the injection pump on this car?

Replace thermostat. If no fix, replace lower radiator hose. Better yet, do both at the same time.

 

[csstevej]

I would change the thermostat with am new OEM one and change the plastic stub pipe that it's in. While the t-stats out you can access the WP through the hole. See if it spins with your finger or screwdriver, also see if it's plastic. Do as Saturn suggests. If the fans don't spin give them alittle shove, maybe there are hanging up/dead spot . If I Rember right there is a fuse on top of the battery that controls the fans, might be wrong , I Rember messing with this on my sons car in the summer. My .02.

 

[karlaudi]

saturnhacker,

Both fans come on with the A/C. The cabin heater alone seems to be the principle means to keep the engine cooler. I concur with your most recent comments. The ambient temperatures have been very cold here in the Bay Area and Northern California. It got cold and very overcast overnight, but rather sunny and warmer yesterday when we picked it up from the dealer.

When the timing belt was replaced the water pump was too, with all VW approved parts at the Dealer I bought the car from in Marin, but I have switched to the San Francisco Dealer for the last two repairs.

[The SF Dealer's shop foreman and two of their top techs hold recent international VW/Audi AG Tech competition top awards, so I do not expect worse service than the Marin Dealer who recently dropped the ball so much that I filed a complaint with VOA/AOA. (VOA gave me a discount toward a new car which led to my purchase of my 2012 TDi.)]

The timing belt and related parts where the latest, 100k interval upgrade, at the time and a very good friend was my service adviser - who understands my expectations very well - at that time, as well. But at this point I have no idea if the impeller is metal or not. Such a pump failure is not out of the question, regardless.

Last night I reviewed the events that led to this problem and now believe that the engine never overheated while my wife was with our oldest daughter, but merely got hotter than normal before they switched the cabin heater on, reduced speed, and watched the temp gauge indicate a reduction in engine temps. The engine coolant warning light came on twice at nearly the exact point on the San Rafael-Richmond Bridge. The first time traveling westbound and the second, eastbound - on an incline section of the bridge. The warning light indicates either overheating developing -OR - below minimum levels in the expansion tank. I knew the coolant was near or slightly below the minimum level in the expansion tank, but the 160k service was scheduled. So this is my theory for the warning light coming on and so far, only at those times.

So I think at those points on the bridge, a bridge we travel daily, the coolant level, engine load, and incline of the bridge all contributed to the coolant warning light going on in both directions of travel.

I am glad my wife and daughter reacted quickly and correctly when the problem arose and monitored it as they went and have safely driven the car for a week now.

My father-in-law, in the same situation, would have, absolutely, no idea what to do - lol.

Current plan of action is to purchase a new t-stat and related parts from VW and install them next week sometime. The Marin Dealer is booked two weeks in advance and the SF Dealer believes according to their tech that every thing is OK, but we cooked the head.

Dealers, like independent shops, are really independent businesses and VOA/AOA has only so much clout in affecting how they conduct themselves on a daily basis. I learned this back in the late 1980s when I was with BMW-NA.

The car is too valuable to us at this point, so if it needs a head at some point, well..... it is mostly original. I still have the original clutch, starter, brake discs, cooling system, etc. Regular maintenance and a new timing belt, plus any updates and recalls are all it has had in its eleven years as a SF Bay Area commute to work car.

 

[karlaudi]

Further note: If the water pump is bad, I will plan to have the timing belt replaced, as it is due at 180k.

 

[csstevej]

If you do make sure it's metal.

 

[saturnhacker]

Well I would definitely start with the stat and like steve said with it out you can see/feel the pump impeller, you just want to be sure it isn't spinning free of the drive hub. A lot of replacement pumps are plastic, even OEM VW.

 

[karlaudi]

Thank you everyone for the input and feedback! I will update this post once the thermostat and related parts are replaced.

Happy New Year too all!

 

[karlaudi]

Completed the thermostat replacement, this past Monday, along with the flange adapter, bolts , o-ring and a gallon of coolant mixed 60/40 with distilled water. Confirmed the thermostat failed closed from 87 too over 100 degrees C in water on the kitchen stove. All parts, but the water, are Genuine VW and the problem is resolved.

However, the ambient temperatures, during the week so far, have been in the 3 to 6 degree centigrade range for most of the day, so I have yet to knowingly cycle the fans, though hot coolant reaches the radiator pass the new thermostat. My Wife is able to have stable indicated coolant temps without the heater on and the car runs well during her commute of about 30 miles each way in stop and go traffic.

I have yet to take it for an extended test drive, but so far so good.

 

[spleecho]

Before you did the t-stat change was the hose on it hot or warm? I am having same issues as you did and my hose is pretty hot

 

[Lug_Nut]

About a week ago ... it starting to overheat... my daughter... deduced to run the heater on full and the engine never got above three-quarters on the temperature gauge, according to them. As long as the heater is on the engine operates at normal temperature.

My dealer ... are saying, ... that though there is coolant flow through the radiator ... the head gasket is blown ... because the upper radiator hose is hot and hard and the lower radiator hose is cool and soft.

The bolded statements are contradictory. You have a working water pump. It's trying to put coolant from the engine into the radiator (hard hose), and trying to suck coolant from the radiator (soft hose). The top hose is hot because the coolant isn't flowing, the bottom hose is cold because it isn't flowing.
The thermostat isn't opening to let coolant flow through the radiator, or the radiator is plugged.


<edit>

Confirmed the thermostat failed closed from 87 too over 100 degrees C in water on the kitchen stove. ....the problem is resolved.

I should have finished reading the thread before composing and posting.....