ALH running hot...boils over under load

[Nuje]

Recently did the timing belt on this car (2002 Golf, Stage4, VNT17, 02M - all the good goodies) - used Hepu water pump. Owner reported losing the coolant (OEM G13) coming through mountain pass (25km climb at ~4-6% grade).
First fix: Replace thermostat (OEM) - same symptoms.
Second fix: Tried early-open thermostat - car ran at 80C (from OBD) on the highway, but then still lost coolant under heavy load (12% grade driving for fun).
Put the new OEM thermostat back in - now it runs ~95C on the freeway (unusually hot) on a drizzly 12C day.

Thought the head might be lifting a bit under that load, so replaced the head bolts with ARP studs. Did the run up the 12% grade again - didn't lose any coolant...provided I backed off before the coolant temp went over 100C; first time doing that, I immediately pulled over and could see the coolant boiling - still at the same level I'd started at); I immediately turned around and started heading back down the mountain (10C outside, so it seemed to arrest the heating and cooled off to mid-90s quickly...down to 89C after a couple km going downhill).

Checked coolant level at the bottom of the hill - normal, where it was when I started.

Then I really pushed up the first few km (12% grade again) and this time, as coolant temp passed 105-107C, it was bubbling like crazy and level had gone down.

In all cases, the radiator fans never kicked on (they work fine if I turn on A/C), and the lower radiator hose that goes to thermostat neck / housing never got anywhere close to "hot". At most, it was warm-ish, compared to the upper hose coming off the flange at the transmission side of head which was always hot-hot.

Why doesn't that lower radiator-->thermostat hose ever get hot? Even when I have boiling coolant in the overflow ball and the upper rad hose is toasty-hot? Is my (new OEM) thermostat a dud? Is the radiator clogged up?
I read this in the manual, but it makes no sense to me (how does a hose collapse in a pressurized cooling system under high rpm?!)

I poured some coolant in the top hose and it did drain out the bottom (drain spigot), so there is flow, but I have no way to know / measure if it's sufficient flow through the radiator.

I also have trouble wrapping my head around the flow of coolant through the thermostat; what direction does the coolant flow through there once it opens?

Any thoughts, theories, suggestions, explanations, diagrams welcome.

 

[Nevada_TDI]

I had a new thermostat fail on me...thinking the new t-sat couldn't be the problem so many hours were wasted. If I had checked the hose with the t-stat first, I could have saved a lot of time and money. Yup, right out of the box it was bad.

 

[jmodge]

A hose collapsing would be from the pump sucking it shut, such as lower hose or anything attached to the coolant tube. What happens if you have your fans running? Though if your lower hose to the pump is cool it is most likely not a fan or radiator issue. They do make kits to check for combustion gases in your coolant, such as head gasket issues. I would suspect lack of circulation, a leak, or a head gasket. Have you put 16 lbs of pressure on the system and let it sit for 15 minutes to see what happens?

 

[JohnTF]

Is the water pump - pumping , maybe impeller gone , broke , seized .
2 /TWO big clues --- no fans when hot , cold hose === no flow !

 

[Nuje]

Is the water pump - pumping , maybe impeller gone , broke , seized .
2 /TWO big clues --- no fans when hot , cold hose === no flow !

Brand new (<5000km) Hepu pump with metal impeller; I can get a finger on it and try to move it when the t-stat is out and it doesn't budge. And I do seem to get flow back into the reservoir / overflow tank with the engine running, so it seems to me that the WP is pumping.
Edit: confirmed that the coolant does circulate back in the reservoir's return line:

 

[Nuje]

Have you put 16 lbs of pressure on the system and let it sit for 15 minutes to see what happens?

I actually did just fashion up a spare Motive pressure bleeder to put onto the coolant reservoir; you're saying 16psi...and after 15minutes, I should still see 15-16psi, correct?

Edit: Just went and opened up the coolant reservoir after the car had been sitting for a few days and there was quite a release of pressure (a lot more than just a little "pshh"); reservoir was below MIN when I'd gotten back from my testing drive on Tuesday (or Wednesday?) and I just left it because I knew I'd be draining it again soon.
So, it would seem to do a fine job of holding pressure.

 

[JohnTF]

Did you say what the temp gauge was saying ?
But cold lower hose & hot upper hose indicates - no flow ?
Fans not coming on when hot - indicates no flow - heat not getting to fan on sensor ?

 

[03TDICommuter]

In all cases, the radiator fans never kicked on (they work fine if I turn on A/C), and the lower radiator hose that goes to thermostat neck / housing never got anywhere close to "hot". At most, it was warm-ish, compared to the upper hose coming off the flange at the transmission side of head which was always hot-hot.

Why doesn't that lower radiator-->thermostat hose ever get hot? Even when I have boiling coolant in the overflow ball and the upper rad hose is toasty-hot? Is my (new OEM) thermostat a dud? Is the radiator clogged up?
I read this in the manual, but it makes no sense to me (how does a hose collapse in a pressurized cooling system under high rpm?!)

Sounds like a bad head gasket and bad coincidence with your timing belt change but not the result of it. Also the coolant flow - isn't it FROM the head to the radiator top, out the bottom and to the t-stat? If so, then the lower hose will always be cooler than the upper as the radiator is shedding the heat like it should be.

edit: the decent pressure after sitting for a few days also suggests head gasket per what I've read.

 

[csstevej]

I have to concur.......it’s going to be your head/head gasket. Head needs to be checked with a straight edge and feeler gauge for warpage.

I had a similar problem with my daily driver, I’m running a Malone stage 3 with sprint 520’s and was have coolant boil out my bottle when I pushed it going up hill , putting ac on ( forcing the fans to come on) helped with temps. I monitor my temps with my scan gauge.

My fans would not kick on also unless I forced them with the ac switch. I’ve come to find out that the fans won’t come on till I believe 112C low speed and I believe 117 or 120 C high speed.

I suspect the small coolant return line is bringing the combustion gases back to coolant ball and “ boiling “ the coolant
( the gas follows least path of resistance ) , I don’t believe it’s hotter than what the gauge is saying R what the fan cool sensor is seeing so that’s why the fans are not coming on.

I also tried arp studs , that helped slow how long it took to boil over but it still did.
I ended up pulling the head , changing the it with a good used from Frans , ( had a major oil leak on valve stems on #4 cylinder when car sat over night ) and pulling TB early too. That was at 394,xxx miles car now has 446,xxx with no issues and I drive it like I stole it, well not now......clocked a deer early in the morning on way to work......waiting on body parts.

 

[03TDICommuter]

Nuje, use your nose to smell the 'air' in the ball. I bet it smells odd.

 

[csstevej]

Also has the coolant ball start to turn black or have any black flakes floating around?

 

[ghohouston]

I had a metal impeller water pump fail, I do believe it was a Hepu. Impeller came right off the shaft. It was a buddies car that I got from him, and he had the timing belt replaced about 20 or 30k miles prior to the event, by a local guru. I spoke with him about it, and he was nice enough to give me a warranty water pump and said he had never seen one of the metal ones fail. I'm an experienced diesel mechanic of over 10 years, 6-7 days a week, and I would have bet money it was a blown head gasket, but when I removed the thermostat, that impeller was off the pump shaft. Car was pushing coolant out of the reservoir and overheating. Damn 6.0's traumatized me lol.

 

[IndigoBlueWagon]

Maybe the water pump impeller didn't move when you tried it because it's jammed, not because it's attached. I don't know if a car overheating with a failing head gasket would have a cold lower radiator hose, but it seems unlikely. And most people say thermostats on these cars usually fail in the open position. Having one (or two) fail in the closed position seems unlikely.

I'd change out the water pump and see if it helps, if only because it's easier and less expensive than a head gasket R&R.

 

[Tdijarhead]

What about a blocked radiator? If coolant is not getting to the lower hose and the water pump is new and IF it’s working and from the return line flow it appears to. How about disconnecting the upper and lower radiator hoses,finding the garden hose and giving the radiator a flush? Cheap fix if gunk is flushed out and you should be able to tell if the volume of water going in is greater than that coming out the bottom.

 

[Nuje]

Maybe the water pump impeller didn't move when you tried it because it's jammed, not because it's attached. I don't know if a car overheating with a failing head gasket would have a cold lower radiator hose, but it seems unlikely.

As much as I'll take a WP replacement over HG any day of the week, given the fairly steady flow of coolant (see photo above) at idle, pretty much immediately after start-up of cold engine that's been sitting for a few days, I'm going to assume the water pump is doing its thing correctly.

 

[Nuje]

What about a blocked radiator? If coolant is not getting to the lower hose and the water pump is new and IF it’s working and from the return line flow it appears to. How about disconnecting the upper and lower radiator hoses,finding the garden hose and giving the radiator a flush? Cheap fix if gunk is flushed out and you should be able to tell if the volume of water going in is greater than that coming out the bottom.

Blocked radiator was kinda my next theory. I'd be all-in on the head gasket theory if the car wasn't running hot all the time (95C on the freeway on a 12C day with a brand new OEM 87C thermostat) and never able to get the lower hose to get anywhere close hot-hot.

Not having a new rad here to A/B test, is there some way to measure how much flow is "good"? Like I said, I did pour some coolant through it before and it made it down and out the spigot at the bottom - but admittedly, it was maybe 200mL slowly poured in. Just run the garden hose in the top and see if/what kind of crud gets flushed out? Run the water through in both directions - or would that be asking for pieces to start shearing off inside the rad on a car with 370K km?

 

[Tdijarhead]

Blocked radiator was kinda my next theory. I'd be all-in on the head gasket theory if the car wasn't running hot all the time (95C on the freeway on a 12C day with a brand new OEM 87C thermostat) and never able to get the lower hose to get anywhere close hot-hot.

Not having a new rad here to A/B test, is there some way to measure how much flow is "good"? Like I said, I did pour some coolant through it before and it made it down and out the spigot at the bottom - but admittedly, it was maybe 200mL slowly poured in. Just run the garden hose in the top and see if/what kind of crud gets flushed out? Run the water through in both directions - or would that be asking for pieces to start shearing off inside the rad on a car with 370K km?

I think I’d just pull the radiator hoses and get the garden hose going if it goes in and starts to back up and over flowing the top with only a little making it through to the bottom I’d say there’s a good possibility the radiator would be partially obstructed.

 

[Nuje]

Sounds good; fence-building day (literal, not metaphorical / relationship thing....although the literal doesn't hurt the metaphorical interpretation either ) so not sure I'll get around to it today, but should have something this weekend.

 

[03TDICommuter]

FWIW, on gassers in the past, they always would flow fine with the garden hose, but would still overheat on the freeway. The cores were restricted from buildup but flowed enough that I could not tell with a hose. Even blocking the bottom, filling them up, then unblocking the bottom, they seemed to flow well. New radiator or a re-core always solved the overheating.
Back when radiator caps were in the radiator itself, you could peer inside and see if the core tubes had buildup.

 

[csstevej]

Maybe the water pump impeller didn't move when you tried it because it's jammed, not because it's attached. I don't know if a car overheating with a failing head gasket would have a cold lower radiator hose, but it seems unlikely. And most people say thermostats on these cars usually fail in the open position. Having one (or two) fail in the closed position seems unlikely.

I'd change out the water pump and see if it helps, if only because it's easier and less expensive than a head gasket R&R.

Ive recently had the thermostat start failing in the closed position.....over a 2 month period temps climbed almost 20 degrees, noticed it mainly going up hills. Replaced with another OEM t stat and all is well.

Out of curiosity , was the car ever serviced with a different anti freeze . I had an issue on a gasser NB where I got the car and it was serviced with the green stuff , I flushed it when I put a new timing belt kit on it along with a water pump but a couple of years down the road it ended up plugging up the port coming out of the head to the coolant ball. It ended up blowing the heater core while idling.....

 

[turbodieseldyke]

given the fairly steady flow of coolant (see photo above) at idle, pretty much immediately after start-up of cold engine that's been sitting for a few days, I'm going to assume the water pump is doing its thing correctly.

It might behave differently at higher temp. I've heard of them stop spinning because the impeller was a different material (maybe plastic) and expanded in the heat. The shaft was spinning but impeller wasn't because it was no longer grabbing the shaft. Then after cooling down the impeller shrank back to its normal size and gripped the shaft again, and spun like normal.

 

[Nuje]

Hepu water pump with metal impeller....while in the realm of possible that it "lets go" under heat, doesn't feel all that probable.
I'd stopped one time to check the lower rad hose while running at 95-96C on the freeway, and peaked in the coolant ball as well - it certainly looked like there was a steady burping of fluid back in to the little catch point for that upper return hose on the coolant ball.

 

[Nuje]

Out of curiosity , was the car ever serviced with a different anti freeze . I had an issue on a gasser NB where I got the car and it was serviced with the green stuff , I flushed it when I put a new timing belt kit on it along with a water pump but a couple of years down the road it ended up plugging up the port coming out of the head to the coolant ball. It ended up blowing the heater core while idling.....

I had the car since 99K km (14 years ago), and then sold it a couple years back and still do maintenance for the new owner. In all that time I only ever used the OEM coolant.
With that said...(and this is long-ago-remembering, but....) I do remember pink in the coolant ball when I bought it, but it was a lot "dirtier" on the inner surface of the coolant ball than expected. So maybe someone early on put in some green goop before someone else said "don't do that"....and it's rearing its head 14yrs later....?

 

[03TDICommuter]

Have you smelled the 'air' inside the ball? And are there bubbles or foam in there when you open it up?

 

[Nuje]

No bubbles or foam but there certainly is a smelly smell inside the coolant ball - some kind of "burned"-ness to it.

I thought it might be the EGR cooler when I put it up on ramps and saw this the next morning...

...but turns out that was coolant that had boiled over and was trapped in the channel that carries the fuel lines to/from the tank. Once the car got tipped back...the coolant dribbled out the channel.

So...we've pretty much settled on the issue being the one we were hoping to avoid: head gasket.
Parts on order. Will do a EGR cooler delete while in there, though, I think; hate working around that thing.

 

[csstevej]

Yeah I’ve deleted all the coolers on my cars.....it does make working on it easier.

 

[03TDICommuter]

Does the cooler delete reduce fuel economy? That’s why I’m not interested in it but I could be reading the wrong info. Also, the EGR readiness flag never gets cleared right?

 

[03TDICommuter]

So...we've pretty much settled on the issue being the one we were hoping to avoid: head gasket.
Parts on order. Will do a EGR cooler delete while in there, though, I think; hate working around that thing.

interested in seeing your progress. I’m going to do mine over the 4th of July weekend.

 

[csstevej]

Does the cooler delete reduce fuel economy? That’s why I’m not interested in it but I could be reading the wrong info. Also, the EGR readiness flag never gets cleared right?

If it does I don’t see it, it may change by a mile or two a gallon..... but then again I’m running a Malone stage 3 with sprint 520’s and averaging 45-48 mpg with 447,xxx miles on the car.
As far as the cel light for the egr I had done the maf twist till I got my tunes done...... probably drove it that way for about 4 years , even paused our state’s emissions.....

The maf twist is easy , what I’ve done is I remove the screws that hold maf sensor to its housing.
With Vcds connected and I forget which channel it is pull up the requested and actual reading on the maf.
Slowly twist it one way or the other till actual and requested are very close , mark the sensor to the housing with a bright sharpie and go drive it.......I leave the screws out as there no reason to keep it in there as there’s no boost and the friction from the o-ring is more than enough to keep it in place.

 

[BuckeyeMan71]

Could also be the switch on bottom left corner of the radiator