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Discussion Starter · #1 ·
Finished up doing the timing belt/thermostat/waterpump and a hand full of other maintenance items on this 2000 Passat 4motion I bought for $300. I flushed the heater core and did a full flush including the block, and now I'm trying to bleed the system but having big problems. I found some other threads describing exactly my problem, little or no heat at idle, great heat at 3-5k rpm. Everything I see says its air in the core, but I can not get it to bleed out. I've gone through $50 in coolant and don't want to waste any more.

My process so far:
cap off coolant reservoir, core bleeder open, engine at operating temp, rev engine several times.

At idle I tried pulling the hose off the core and I wasn't getting any flow from the bleeder side of the core at all at times, and just a trickle at others. I'm really at a loss at this point, what am I doing wrong?
 

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leave the cap on the reservoir - you need pressure to build up in the system. warm the car up, and then have someone hold the accelerator pedal down at 3000 RPM, and then try bleeding it.
 

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Discussion Starter · #3 ·
Just tried it like that. Topped off the reservoir, put the cap back on, brought the car up to temp and had the wife hold it at 3k. I opened the bleeder and let it sit for 15min at 3k and still no heat. It looked like it was purging some air, bubbling and steaming, but never got a good stream of coolant from the bleeder. I closed up the bleeder and it was back to good heat at 3k, cool air at idle...
 

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I had this problem as well. I fixed it this morning by following http://www.passatworld.com/forums/61-b5-information-base/330868-v6-coolant-flush-diy.html
I removed the hose clamp on the heater core bleed hose and loosened the hose but did not pull it back to bleed it yet. (I had to gently twist the hose back and forth with channel locks to break it free).
I removed the 3 mounting screws from the reservoir and took the cap off.
I filled the reservoir and started my car for about 5 min. I turned the car off and confirmed the pump was working by observing the stream of coolant circulating back to the reserviour.
I pulled the bleed hose back and picked up the reserviour and tilted it so the coolant level was higher than the heater core at all times.
I waited till the gurgling subsided and coolant ran out of the bleed hole on the hose. I pushed the hose back on and reclamped while holding the reservoir up.
I reattached the reserviour and put the cap back on.
I ran the car semi aggressivly on the highway for a few minutes.
The heat is better after doing that twice. I DID NOT take the cap off after the car was up to operating temperature. I let it cool and repeated the steps above.

Good luck!
 

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Just tried it like that. Topped off the reservoir, put the cap back on, brought the car up to temp and had the wife hold it at 3k. I opened the bleeder and let it sit for 15min at 3k and still no heat. It looked like it was purging some air, bubbling and steaming, but never got a good stream of coolant from the bleeder. I closed up the bleeder and it was back to good heat at 3k, cool air at idle...
based on my experience, your heater core is likely clogged and will need to be replaced.
 

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Discussion Starter · #6 ·
I had this problem as well. I fixed it this morning by following http://www.passatworld.com/forums/61-b5-information-base/330868-v6-coolant-flush-diy.html
I removed the hose clamp on the heater core bleed hose and loosened the hose but did not pull it back to bleed it yet. (I had to gently twist the hose back and forth with channel locks to break it free).
I removed the 3 mounting screws from the reservoir and took the cap off.
I filled the reservoir and started my car for about 5 min. I turned the car off and confirmed the pump was working by observing the stream of coolant circulating back to the reserviour.
I pulled the bleed hose back and picked up the reserviour and tilted it so the coolant level was higher than the heater core at all times.
I waited till the gurgling subsided and coolant ran out of the bleed hole on the hose. I pushed the hose back on and reclamped while holding the reservoir up.
I reattached the reserviour and put the cap back on.
I ran the car semi aggressivly on the highway for a few minutes.
The heat is better after doing that twice. I DID NOT take the cap off after the car was up to operating temperature. I let it cool and repeated the steps above.

Good luck!
I will give this method a shot. I haven't tried elevating the coolant tank yet, hopefully it does the trick, thanks!

based on my experience, your heater core is likely clogged and will need to be replaced.
This is a portion of the build thread I have going on another forum:

Small update:

I didn't get as much time in the garage as I would have liked, but made some progress none the less. Decided to flush the heater core and see what would come from doing so.

This is what I found when I pulled the lines off...Should be a bleeding pin hole in the top of whats left of the left nipple...


This is what I got the first time I flushed it.



After that mess cleared up a bit I filled the core with CLR and let it sit for an hour.


Looks like its on life support, lol.


I used a fish tank flusher to do the job, and it worked very well. Had to get a couple feet of 3/4" clear tubing to fit the core nipples, then a couple reducing barb fittings to fit one to a garden hose (drain) and the other to the fish tank flusher (feed). This allowed me to flush from my kitchens sink, and use hot water.


After a couple flush>CLR>flush cycles it started coming out pretty much clear.

On the plus side, since I was using HOT water to flush the core, I turned the car on to acc position, fired the fan up to high, set the vent to dash, and viola! It was blowing good and hot!
Do you still think my core could be clogged?
 

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Discussion Starter · #8 ·
Just gave it a read. Not sure I'm ready to try a pressure washer yet, maybe as a last resort. If the core was clogged would I get heat at higher RPM? I thought this was a symptom of air trapped in the core. From what I've read, clogged core presents as loss of heat at any RPM, and air in the system is RPM dependent, is that wrong?
 

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Discussion Starter · #9 ·
So I was just messing around in the garage and noticed my coolant reservoir was bone dry...It had coolant in it when I parked the car yesterday. What would cause this? No leaks that I can see, oil looks fine.
 

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if the pix above are the OP's, it leaked out of the return side of the heater core - that bit of plumbing is shot. I know, I've been there before.
 

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if the pix above are the OP's, it leaked out of the return side of the heater core - that bit of plumbing is shot. I know, I've been there before.
Same here, tried multiple repair attempts.
In the end I bit the bullet and replaced the heater core.
 

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it is leaking while the engine is running and after, due to pressure in the coolant system. when it is that broken, you can rarely (if ever) get it to seal correctly.

some have reported (and posted here about it) that they can get a good seal by using a piece out of a Prestone flushing kit and epoxying it in with JB Weld - I have done so on one car, and the core wasn't so far gone as to allow me to get good heat; however, on another, the core just had to be replaced due to the broken nipple and core clog.
 

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Discussion Starter · #16 ·
update: car is back on the road after a new coolant reservoir and cap, with a full G12 flush. Runs like a top, trans shifts are 'eh', and I'm getting a nasty rhythmic vibration from the front end at speeds over 50-55mph. I'm getting the trans topped off and the snow tires mounted up so I'm hoping that will solve the issues. I'm confident the trans will be fine once its got the proper amount of fluid in it, but I'm not so confident new tires will fix the vibration.

Its a very odd vibration I've never experienced before. Rhythmic thump-thump-thump.......thump thump thump.......thump thump thump over 50mph, very strange. Its coming from the side I just put the new CV in, so when we're mounting the new tires I'll check that all the CV bolts are tight. I have a sneaking suspicion the bolts holding the CV to the trans are loose. I'll update tomorrow.
 

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Its coming from the side I just put the new CV in, so when we're mounting the new tires I'll check that all the CV bolts are tight. I have a sneaking suspicion the bolts holding the CV to the trans are loose.
I always use Loctite on such short bolts as those and the crank pulley. Also, give a description of how your trans shifts. Why do you think it needs to be topped off, and what makes you confident that will be fine?
 

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Discussion Starter · #19 ·
did you put in an entire axle, or did you change the CV joint?
Entire axle. It came wih the car, the PO never installed it. Its an aftermarket bar stock type, not the OE tube style.

I always use Loctite on such short bolts as those and the crank pulley. Also, give a description of how your trans shifts. Why do you think it needs to be topped off, and what makes you confident that will be fine?
Yeah, going to put some loctite on if they are indeed loose, will be checking shortly. The PO tried draining the trans pan and refilling it, but he didn't refill with the car running so it has to be a bit low. It just slips a bit when cold, or when going through a long sweeping corner.
 

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Discussion Starter · #20 ·
ok, good news and bad news...

The Passat is good to go! The new tires totally fixed the vibration and she runs straight and true as an arrow. I am still getting a little clicking from that aftermarket CV axle, so I'll be ordering a rebuild kit for the OE CV I pulled out. It should be good for a while as long as I can stand the clicking. The muffler is swiss cheese so its got a nasty drone on the highway, but I can live with it for now. It also has a hard miss when it goes into OD and the rpms drop. Only happens when I put it under just enough load to bog the engine down a bit but not enough to get the trans to kick down. I'm assuming the plugs haven't been changed for a LONG time, so we'll see if a fresh set solves that problem. I haven't topped the trans off yet, that will happen tomorrow after work, but once its warmed up it shifts just fine.

Why was the car vibrating? Because both front wheels were bent, and full of Slime...what a mess.



Bent wheels balanced fine, so I threw them on the rear and they ride fine.




It still needs some odds and ends, but I'm going to start driving it to work tomorrow. Which leads to the bad news...I knew my truck has been in need of brakes for a while, considering its been 55k miles since I last serviced them. Well, the last few days its been getting pretty bad, and the right rear caliper started sticking. Sticky slide pins are common on these trucks, so no surprise. Well, as I was pulling into the tire shop to get the Passat wheels balanced I felt a pop and the brake pedal went to the floor as the ABS and Brake lights came on in the dash...Turns out the inner pad fell COMPLETELY OUT of the caliper, and the piston popped out dumping fluid everywhere. :( So I limped it home and parked it until I can do a full brake job and replace that caliper.

So needles to say, the Passat is now my primary car for the time being.
 
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