Coolant loss and overheating, what's the solution?

[TurboABA]

I'm assuming a 2015 with 130k miles is out of emissions warranty, and I'm on my own on this.

Don't assume anything..... check

VW Emissions Modification Lookup

www.vwdieselinfo.com

Warranty Period
The warranty period for the “Extended Emissions Warranty” limited warranty extension shall be the greater of:
 11 years or 162,000 miles, whichever occurs first, from the vehicle’s original in-service date;
OR
 5 years or 60,000 miles, whichever occurs first, from the date and mileage of Phase 1 of the emissions modification. At the time of the subsequent Phase 2 modification, the extended warranty will be honored for 5 years or 60,000 miles, whichever occurs first, from the date and mileage of the completion of Phase 2.

 

[740GLE]

Furthermore, I just noticed something very interesting, which I had previously overlooked.

This might have significantly decreased your EGR cooling and the overall ability of the ECM to properly apply thermal management as intended.
Your DPF will also be fulling up at an accelerated rate as a result.
You can easily check your soot\ash loads with VCDS as well as get some clarity on how often active regens are taking place, etc.

How in the heck would a non shrouded WP increase DPF soot content? There is no feed back to the ECU that the water pump shroud is retracted, so it has no idea if it's there or not unless you scan for it. Gen2 Passats didn't have this type of water pump and very similar coolant system, are you saying those DFPs sooted up faster?

Are you saying that because coolant flows more freely, soot generation is higher? That's a mighty big stretch right there. EGR cooling is only needed when temps are high, if that pump doesn't have the shroud, coolant will be keeping things in check, maybe warm up times are slightly longer.

My guess is for some of these overheating issues come from some of those countless check valves in the system locking shut/clogged up, but just a guess.

 

[IndigoBlueWagon]

Restricted water pump flow shortens engine warm-up time. That's the only condition where it helps. If it has any impact on soot generation it's extremely minor. But every little bit helps when you're striving to ensure your emissions are "legal."

 

[TurboABA]

Correct... You're increasing warmup time. Everything from egts to EGR goes out of wack and that's what makes soot faster. During warmup the engine doest run at optimal efficiency from what I know

 

[pedroYUL]

I did change the timing belt in my wife's GSW CRUA engine for the non-variable speed one from IDparts...didn't have issues bleeding coolant, just refilled the bottle, no issues at all with overheating, no noticeable (cabin heat) difference in heat-up speed.

Lucky?

 

[1854sailor]

TurboABA, your comments are understandable, given that you're working with limited facts. However, IMHO the condescending nature of your comments shouldn't have a place on a forum designed to help people solve their problems.

After I towed the car home, I topped it up with coolant and began driving normally, although I carried a jug of antifreeze in the back at all times.
During the next 6 weeks, I drove over 3,500 mostly highway miles without adding coolant, and had no discernable coolant loss. I checked the level every couple of days, and it remained just below the top line on the expansion tank. This included a 600 mile round trip over Labor Day to the same destination on which the car had previously overheated. I had the bikes on the back but didn't have the roof rack and 2+ foot tall luggage bag on top. The ambient temp was about 5 degrees cooler, but I drove the same speed as before.
If I have a head gasket leak or some other underlying cooling system issue, it is apparently no longer causing problems.

Additionally, the coolant blowing out the reservoir thread has 73k views and 320 replies, with at least 20 people claiming that they are experiencing the same problem. That seems to me a good deal of evidence pointing to an issue with the EA288 cooling systems, specifically that under certain conditions, DPF regen cycles will trigger coolant loss.

I haven't had a chance to do a pressure test or combustion leak coolant test, but that's next on my list.

I monitor both of ours with ScanGauges and have never seen a significant rise in coolant temperature during a regen on either car...

 

[RIP TDI]

I did change the timing belt in my wife's GSW CRUA engine for the non-variable speed one from IDparts...didn't have issues bleeding coolant, just refilled the bottle, no issues at all with overheating, no noticeable (cabin heat) difference in heat-up speed.

Lucky?

Did you happen to notice if your original pump's shroud was stuck in the retracted position (i.e., impeller uncovered)?

 

[pedroYUL]

Did you happen to notice if your original pump's shroud was stuck in the retracted position (i.e., impeller uncovered)?

Nope, I was oblivious of this whole ordeal for some people. I guess ignorance is bliss, I presumed the system to be just a step up from the simple mk4 system, I pulled the old pump, transferred the solenoid to the new one, topped up the coolant and done...like an mk4...sorta.

 

[740GLE]

Correct... You're increasing warmup time. Everything from egts to EGR goes out of wack and that's what makes soot faster. During warmup the engine doest run at optimal efficiency from what I know

IMO soot is a factor of load more than temp, I'm with Peter, if any impact on soot generation it's absolutely miniscule.

 

[TurboABA]

I interpret VAG's documentation differently but don't have any data to quantify the different soot generation rates.

Engine Mechanics
Thermal Management
A thermal management system controls the cooling system in the EA288 engine. The thermal management system is used for optimum distribution of the available engine heat while taking into account the heating and cooling demands of the interior, engine and transmission. The thermal management system heats the engine quickly in the warm-up phase after a cold start. The heat produced by the engine is directed to the components of the cooling system in a targeted manner. Using the heat available in the cooling system efficiently reduces internal engine friction, which reduces fuel consumption and exhaust emissions. The interior of the vehicle is also brought up to a comfortable temperature quicker.

IMO manufacturers wouldn't have designed\developed\implemented all these additional fancy devices to help meet restrictions if their impact was absolutely miniscule.... but once again, I don't have any data to support this.... just my logic.

 

[IndigoBlueWagon]

EPA emissions testing is based on a "test" (it's actually a simulation or an extropolation) that is biased towards cold start and warmup along with low speed highway. The nature of the test exaggerates warmup time compared to what most experience in use. And manufacturers have gone to great lengths for little gain to get under the emissions ceiling.

And I can't help but think of the irony in all this, given dieselgate.

 

[Tdimrtwo]

The o.e. electronically controlled water pump is designed to restrict coolant flow during cold starts. It has an electrically-controlled, movable shroud around the impeller that extends to cover it and prevent it from pumping. This allows the engine to get up to operating temp more quickly to improve thermal efficiency. That’s its only purpose, and once up to temp, the shroud stays fully retracted until the next cold start. The water pump doesn’t control egr cooler temp or have any other thermal management function. But it is highly prone to leakage and bearing failure. This has occurred as early as 55k miles, and is well documented on this forum and numerous YouTube repair videos. ID parts (a well respected VW parts source) supplies an aftermarket non-electronically controlled water pump with their T/B kit, and highly recommends its use, although they will sell you an o.e. electronically controlled pump if you really want one. Febi (VW supplier) has a good YouTube video describing the issue.

So what do I really know?
1. The car was losing coolant before I changed the TB and WP, and the only visible sign of coolant loss was from the reservoir overflow. I might not have seen a really small WP leak, and overfilling the coolant bottle could have resulted in this condition, but I’m quite sure that I only filled it to the top mark on the bottle.
2. I still had some coolant loss after I replaced the TB/WP and the engine lost coolant repeatedly and finally overheated on a long hard trip. One crucial piece of information is that I did not properly purge the air from the system using Vagcom.
3. In the 6 wks since the engine overheated, it has worked perfectly. I haven’t added any coolant, or experienced any drop in level at the bottle.

So is my problem resolved? Probably not, since it was somewhat intermittent to begin with. Hard to say exactly what caused it, maybe I left an air pocket in the engine when I changed the WP. Maybe high engine loads caused excess soot production and required frequent dpf regens thus boiling water out of the overflow. I may never know for sure.

I think that my best course of action is:
1. use vagcom to correctly bleed the cooling system.
2. Pressure test the system and do a combustion gas test to verify that there isn’t a leak or head gasket problem.
3. Monitor the soot loading and dpf regens and see if there’s a correlation between dpf regens and coolant loss.

 

[pedroYUL]

... I did not properly purge the air from the system using Vagcom.
3. In the 6 wks since the engine overheated, it has worked perfectly. I haven’t added any coolant, or experienced any drop in level at the bottle....

I didn't do the prescribed procedure for bleeding either and don't plan to do it. It sounds to me that it is german analism for the existence of that procedure, why?

When you change the water pump, only the block and reservoir are affected, that is (in this new design) a closed system. If you don't disconnect anything else that carries coolant, but the water pump, and refill the reservoir when you are done, there should be no air ingested anywhere else!

That closed loop WP/block, is vented via the reservoir which is using gravity and the WP action to purge air, hence it should be self purging. Now if you disconnect the radiator trying to drain coolant before disconnecting the WP (to make less of a mess), then you would have to perform the VW mandated purging procedure.

A personal story (single data point): with my mk4 wagon BEW engine, I did experience what I now think was a head gasket snafu. I was driving at highway speed and suddenly get a CEL and perhaps some other warning lights, this was probably back in 2008 or 2009, my car is 2004 and at that time it only had perhaps 80k km.

Anyway, car drives fine I pull over into a rest area a couple of km away, open the hood, no VCDS, seemed that there was a tiny bit of oil or soot that passed into the coolant, I could see a black ring inside the bottle that wasn't there before. A little coolant was missing, perhaps half a litre, top off with water. Engine seemed somewhat on the warm side of the range. Waited a little until it cooled off and continued my trip....

For the next probably 2 months and then sporadically, I tried to make sense of what happened that day. To this day I have no explanation, CEL cleared on it's own same day or the following, and I still have the car now with 420k km....drive more, worry less, as I've seen been quoted by someone else in this forum!

 

[740GLE]

knowing that the coolant resivoir is shared between the block coolant loop and the A2W intercooler loop, my only hunch is that something happened with the A2W coolant pump/or thermal load of the A2W IC was exceeded and caused the boil. Maybe that system some how was syphoned low when the WP was changed out?

I'd say sounds like you need to throw that roof top box on and load up the car with 700lbs and set off for a 300 mile trip cruise set at 85mph, monitor CIAT and DPF regens, see if you catch it again. Sounds like a fun day behind the wheel.

 

[Tdimrtwo]

knowing that the coolant resivoir is shared between the block coolant loop and the A2W intercooler loop, my only hunch is that something happened with the A2W coolant pump/or thermal load of the A2W IC was exceeded and caused the boil. Maybe that system some how was syphoned low when the WP was changed out?

I'd say sounds like you need to throw that roof top box on and load up the car with 700lbs and set off for a 300 mile trip cruise set at 85mph, monitor CIAT and DPF regens, see if you catch it again. Sounds like a fun day behind the wheel.

Good advice, That’s exactly what I intend to do.

 

[sootchucker]

just to clarify, VAGCOM bleed does NOT open the one way valve the same way ODIS does.

 

[Tdimrtwo]

So it's been about 8 months since the overheating incident. So far, I had to add about 1 cup of coolant when the temp got down to 16 degrees F, but otherwise I haven't lost a drop. So apparently my water pump was the initial leak, and I cured it with the timing belt/water pump replacement. Shortly afterwards, I overloaded the cooling system driving 85 mph uphill with a 3 foot tall loaded roof rack. It seems that my cooling system can't reject all the heat that the engine can make when it's really running hard. Maybe I need a radiator upgrade or additional cooling fans? Anyone have a similar experience?

 

[TurboABA]

I'd say you're better off investing in a more aerodynamic roof box system....
If you need that kind of carrying volume, consider a hitch carrier or a small utility (or custom) trailer setup.

 

[1854sailor]

I'd say you're better off investing in a more aerodynamic roof box system....
If you need that kind of carrying volume, consider a hitch carrier or a small utility (or custom) trailer setup.

 

[TurboABA]

Furthermore, I'd consider something like this

Luggage trailer for motorcycles, bike, roadster and cars

The ideal low cost solution for a trailer to go with your motorcycle, your roadster or your car.

luggandroll.com

 

[ticaf]

Shortly afterwards, I overloaded the cooling system driving 85 mph uphill with a 3 foot tall loaded roof rack.

What was the temps reading?

 

[Tdimrtwo]

I'd say you're better off investing in a more aerodynamic roof box system....
If you need that kind of carrying volume, consider a hitch carrier or a small utility (or custom) trailer setup.

I have a 5x10 utility trailer that I could have taken, but my car came with a DSG transmission, and VW doesn't allow towing with it. I also have a hitch carrier, but I already had a bike rack on the hitch, so that wouldn't work either. I have a Mercedes Sprinter van that is great for road trips, but it was getting an engine swap at the time, so that wasn't an option. Anyways, this was a once-in-a-lifetime vacation to Yellowstone, so It's unlikely that I'll need to carry that much stuff in my Sportwagen again.

 

[Tdimrtwo]

What was the temps reading?

Temps read slightly above normal until the coolant boiled out, then it went to full hot almost immediately. But, I shut it down right away, so I didn't warp the head or damage the engine.

 

[sootchucker]

Temps read slightly above normal until the coolant boiled out, then it went to full hot almost immediately. But, I shut it down right away, so I didn't warp the head or damage the engine.

this is not normal. who replaced your water pump/bled your cooling system?

 

[Tdimrtwo]

this is not normal. who replaced your water pump/bled your cooling system?

I replaced the Timing belt and Water pump myself at 120 k miles. Didn’t know to do any special bleeding on the system, but everything seems fine now. Now at 155 k, and no issues since the single overheating episode. I’m convinced now that I just overwhelmed the cooling system with the combination of heavy load, high roof bag, and long uphill climb. (800 ft to 3600 ft). We don’t really like to admit that our cars have limitations, but I think I discovered one on this trip.

 

[oilhammer]

Old(er) thread, but I thought I'd post here... just had a 2015 CRUA G-wagon towed in yesterday, slow loss of coolant and eventual overheating. No external leaks. Removed the glow plugs and pressure tested overnight, coolant in #3 cylinder this morning.

154k miles.

 

[RIP TDI]

Old(er) thread, but I thought I'd post here... just had a 2015 CRUA G-wagon towed in yesterday, slow loss of coolant and eventual overheating. No external leaks. Removed the glow plugs and pressure tested overnight, coolant in #3 cylinder this morning.

154k miles.

Interesting data point; 1st leaking head gasket report I've seen.

 

[r90sKirk]

Fatigued head gasket, then?

 

[pedroYUL]

Is that just a head gasket situation, or bigger job than that?

 

[oilhammer]

No history on this one, never been here before. It does have a brand new DPF assembly on it, not sure why but it may have just been that "just because" parts replacement deal on the 3rd gen cars with the stupid Dieselgate deal. And of course it's all butchered up.

Sent him to the dealer with the warranty info in hand, we'll see what happens but I bet he'll have to fight it.

No idea what's wrong specifically, or why. My only experience with the CRUA/CVCA beyond normal PM is one engine replacement I did after a DIYr tooefed the timing belt job and ruined the engine. And a couple CKP sensors. That's pretty much it. All I know it is a VERY complicated engine assembly. Over 16hr labor just to R&R the head on one. Which has to be one of if not the highest amount of time on any belt-driven inline four cylinder I can think of.