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W12 Hard hot starts

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73blazer

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2005 W12
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Discussion starter · #1 ·
I really need to solve this issue. This car has had it since I acquired it in early 2020.

When you get my W12 up to full operating temp and shut it off, if you try to restart it in less than 30mins, it cranks over really really hard as is slowly, . It sounds as if the starter isn't getting full voltage or something is actiing heavily on the mechanics of the engine causing it to be hard to turn over. And sometimes, it won't start at all. It will crank for like 1s or less and stop. If you wait a few mins, try again, it may not start again or it may start. And to get it to try again after a failed start you have to remove the key and open the door. Yes I've done the key left to bridge the batteries and it doesn't help the hard turnover when hot at all. It's never stranded me. I can always get it to start usually just by waiting a few mins and trying again. But is very disconcerting.

I don't think it's battery. In bridge mode, it spins over same slow hard rate when hot. When it's cold it spins over super fast. The start batt has a sticker on it dated dec 2019. I can leave the car sit for weeks with no charger on the start batt and it spins over super fast. It only does this when it's hot. If you leave it for 45mins or an hour, the engine is still warm but it spins over normally. There are no codes associated with it even when it does the crank half a second and stop thing.

What's normal on a W12? Does everyone's W12 spin over very slowly when it's hot? Generally engines usually turn over better when hot or warm. Not quite sure how to troubleshoot this one. I'd love to trying turning it by hand mabey with a torque wrench to see how much torque it takes when cold and hot to feel how much effort it takes but there's not good way I know of to turn these by hand without taking some stuff apart.

Next time I take it out I'll take a sound clip of the cold and hot starts. It's very noticible. Much more struggle for it to turn itself over when hot.
 
#2 ·
My w12 spins over much slower than my v8 did. But it has a lot more parts and mass.

I’d be afraid your starter might be dying.

On clothes dyers, the symptom is hard start when hot, normal when cold- until the motor dies completely.

Not sure if that applies to car starters- but both are electric motors.


Sent from my iPhone using Tapatalk
 
#7 · (Edited)
Your tale of woe reminds me of my Scirocco.

My 1988 Scirocco would not turn over when it was hot in TX. It acted like the engine was seized. I would turn on the key, put it in neutral, get out, push it, jump in, press the clutch pedal, put it in gear and pop the clutch. It started every time.

After I moved it up north in 1992, it started every time without needing a bump start. All I did was move it up north. This century, I heard that changing the starter for a diesel starter would end the hot soak starter problems. I ordered a diesel starter but it wasn't plug and play so I never installed it. My Scirocco has problems but hot starting isn't one of them.

I have no idea how old the starter batteries are in my Phaetons. 8486 had a larger (but still wet cell) starter battery. 7579 has the standard size.

Both my 2004 V8 and my 2004 W12 have new left batteries but the starter batteries came with the cars.

I don't notice any difference in the starter speed between the V8 and W12. They are just running right away. I will have to pay attention next time to see if their starters spin long enough for me to notice.

I turn the key to the right on my 2004 W12 (VIN 7579) and it just starts. I let go of the key and the starter spins the engine the same no matter if the engine is cold or hot. I never even notice the starter sound. The engine catches right away, usually before I take my hand off the key.

2004 W12 (VIN 8486) was the same way but the previous owner had the KESSY die. The starter turned over to death as is normal on the W12 with a flooded KESSY. It came to me with a new KESSY and starter. The new KESSY in 8486 required a foot on the brake to start. 7579 can be started without pressing the brake pedal.

Perhaps a previous owner had a flooded KESSY on your Phaeton but they kept the original starter.
 
#8 ·
Plausible theory, but still sounds like the starter needs to be replaced. ☹. Last thing you want is for it to stop working >AAA tow home.😬 If you don't have AAA.....well worth the investment. Will cover all your cars and will pay for itself the first time needed.
I have 9 (8VW) cars licensed and insured, only 2 <100Kmi; 3 >200k.....😎
Mark
 
#11 ·
It looks like the missing link was supposed to be for elsaweb but the rest of the address is (now?) garbage.

elsaweb likely has the original directions which Powerdubs summarized.

If elsaweb has a procedure to replace the W12 starter without removing the engine, that sounds like a good starting point. You can probably get away without removing a lot of stuff but you probably have to play it by ear.

I think the part about draining fluids might be worst case scenario. Even if the lines have to be moved, I think you could cap them off instead of draining everything. I'd be prepared to do everything but try to do the least amount of other stuff removal.

That's where experience helps. Somebody who has done the job would know what sizes of hardware to cap off lines and stuff.

I would only drain fluids if it was time to change fluids anyway. Maybe use brand new pans to catch and reuse the fluids if draining fluids can't be avoided.


7579 had its engine out twice according to CarFax. Once to work on the transmission and once to replace the transmission.

8486 had its engine out at least once to replace the starter as part of the KESSY replacement.

I have thought of buying the W12 support rack in case I ever want to drop the engine but haven't yet.

The Snapon VW tools website is being obstinate now or I'd find and link the W12 support rack. I think it was relatively cheap. Cheaper than the jack you would need to lower and engine and transmission.

As I recall, the bottom support rack is also cheaper than the upper support bar (that holds the engine up if you remove everything under the engine). However, you could make your own or buy a cheaper engine support bar.
 
#12 ·
I found this in my Phaeton folder. It has a flowchart for if the starter doesn't work but may also help if it's turning slowly. Notice that it says "A defective change-over relay can sporadically or permanently cause malfunctions when starting."
 

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#14 ·
Phaetonlvr said:
Haven't seen a write-up on this either but I think Robert was planning on doing that job a while ago. Maybe he's got more info.
Click to expand...
As they say, plans change ;). But joking aside, I was indeed planning on undertaking this job. However as time progressed the noises heard from the engine almost certainly warrant an engine removal. I received a quote from an experienced and qualified workshop that would entail basically mounting a factory-new engine. Last Friday I had a buddy over who's experienced at overhauling transmissions and engines. From listening to it he thought it might even be a rod bearing issue. Suffice to say the engine is unfortunately very, very ill. :rolleyes:
 
#16 ·
Did we ever figure out if VR6 or VR8 engine internals like bearings, pistons and rings would fit?

If I (speaking as me) owned an engine parts company that made such items for other cars, I would make them for the W12 especially since VAG doesn't seem to have them in their catalog.

You would think at least one of the bosses of an engine parts company owns a Bentley or Audi or maybe even a Phaeton.
 
#17 ·
Robert.Vangeenen said:
As they say, plans change ;). But joking aside, I was indeed planning on undertaking this job. However as time progressed the noises heard from the engine almost certainly warrant an engine removal. I received a quote from an experienced and qualified workshop that would entail basically mounting a factory-new engine. Last Friday I had a buddy over who's experienced at overhauling transmissions and engines. From listening to it he thought it might even be a rod bearing issue. Suffice to say the engine is unfortunately very, very ill. :rolleyes:
Click to expand...
A little update. It's my plan to pick up the Phaeton from the workshop next week. Can't wait to experience the smooth purring of 12 pistons the way Old Man Piëch intended. :love:
 
Discussion starter · #19 ·
Oh yeah, i went to start it today cold and she was turning slow. After 40mi where I wanted to go i shut it off. Shopped for 1hr, came out, very slow turnover and no start. Did the left key to link batteries, still, very very slow and no start. Wait 5 mins. retry, turns slow but barely starts. it's not low voltage. that starter just doesn't want to turn it. I've done so much to this car and it's running good. But this starter issue could be a death sentence if I can't get it changed.
 
#20 ·
Not good. I have not had starter issues so have not looked at/tried to change in situ. How many miles? Wonder if you can support engine and drop subframe to get at it. Big job with a garage and plenty of time required....did you check the cable for evidence of overheating/connection/corrosion at the firewall jumper station?
Mark
 
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Phaeton4me
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