Heater Core Plugged 2005 Passat TDI

fastcar4re · Sep 18, 2014

A few months ago I had my heater core back-flushed to again have it let hot water pass through it so that my A/C was not forever freezing me out here in Houston. I suspect I regained about 30% functionality and that was fine. The heater core is now plugged again - no heat. This is an expensive repair for what is an inexpensive heater core, because the entire dash has to come apart.

My question is, how many of you have had the same problem and what are your fixes. Did you attempt the job yourself or free up your wallet for the labor of someone else who would take on the job? Thanks again.

johnboy00 · Sep 18, 2014

I know that some have cycled CLR through the heater core to clean it out. All you need is two hoses a bucket and a small pump. Place the pump in the bucket with a solution of CLR and water (presumably hot). Pump the water into one end of the heater core while returning the other end to the bucket. Let it run. Change water/CLR as needed.

Since you only got 30% throughput after the last flush, is it possible the system was not completely bled of air? Do you hear any gurguling? You may want to check if there is any air in system. The layout of these systems seems to cause the heater cores to not flow, if residual air is in the system.

Shenandoah · Sep 18, 2014

fastcar4re,

I replaced the heater core in my 2004 Jetta sedan. What a chore! It's not hard but as you've said, you have to take the whole dash out. The hardest part was pulling the heater back from the firewall to slide the heater core out the top. I thought for sure something was going to break.

In looking at all the work and what has to come out, I can understand the price.

Eric

vwztips · Sep 19, 2014

First check to make sure that your engine is truly getting to 90C via Vagcom. I have seen plenty that showed 90C on the dash but were only getting to 70C-80C due to a weak thermostat, opening prematurely. Much cheaper and easier to experiment with.

gregc · Sep 19, 2014

I'm going to flush my core as johnyboy stated. I got a small pond pump from harbor freight for ~$10. I already flushed it once with regular flush and a hose. It was nearly completely plugged. This time I'll use clr and let it circulate for a while. Plan to put a cloth/sock over the end of the hose to catch any gunk.

1854sailor · Sep 20, 2014

It would be interesting to see if there's a correlation between heater core plugging and improper (non G12or G13) coolant usage.

50harleyrider · Sep 29, 2014

1854sailor said:
It would be interesting to see if there's a correlation between heater core plugging and improper (non G12or G13) coolant usage.

Absolutely. Wrong coolant muds the tdi's and gassers up in no time. Also deionized or distilled water for the 50% dilution is necessary for long term health too.

oilhammer · Sep 29, 2014

Yep, that's why it happens. The B5's heater core seems to have little tolerance for foreign coolants contaminating and mudding up the system.

I've had pretty good success flushing them out, though. It may take a few times, and a garden hose, but I've never had to replace one because of this.

toastystew · Sep 30, 2014

I have had the same problem, and have tried the flush. The air got hotter, but not as hot as i was expecting. I also replaced the thermostat, and flushed and repaced the coolant, which seems to have helped more than the flush. I think i read on a thread whilst i was reading to learn how to do the aforementioned jobs that some folks were somehow capping the CLR in the core for a little while like a day or two then using a garden hose to flush the core out. I didnt try that because i didnt have time.

50harleyrider · Oct 1, 2014

If a previous owner had used tap water in the system even with G-12, the salts in the tap water have probably fouled the core and a simple water flush won't dissolve them and heat transfer won't be very good. Can't recommend a more aggresive chemical flush due to the sensitivity of VW components. If you're sure your thermostat is functioning properly, you may have to replace.

gootie · Oct 6, 2014

Why do these cores plug even with strict adherence to coolant/distilled water specs. This does not seem to be a problem with other VWs.
Maybe the picture here explaies : http://www.passatworld.com/forums/68-b5-garage/338139-heater-core-teardown-pix.html#post2810016

gootie · Oct 6, 2014

gootie said:
Why do these cores plug even with strict adherence to coolant/distilled water specs. This does not seem to be a problem with other VWs.
Maybe the picture here explaies : http://www.passatworld.com/forums/68-b5-garage/338139-heater-core-teardown-pix.html#post2810016

Those flow diverter rods must reduce flow thereby increasing tendancy for coolant to eventually sludge. Then there is the issue of core placement above engine and the reservoir. There likely should have been a flow boosting pump in this system . Local dealer is not using the actual VW core probably for customer cost complaint reasons but I thinking the lower resistance unit will be less likely to sludge up if coolant integrity is maintained.
It has been reported that there is a small bypass channel high in the original cores that will allow for both inlet and output connections to be hot even if the lower core area is plugged.

oilhammer · Oct 6, 2014

Neither of mine have ever had this issue, nor have any of my regular customers. Every time I see it, there is clearly (no pun untended) sign of contaminated coolant. All cloudy and grainy looking.

gootie · Oct 6, 2014

oilhammer said:
Neither of mine have ever had this issue, nor have any of my regular customers. Every time I see it, there is clearly (no pun untended) sign of contaminated coolant. All cloudy and grainy looking.

I am writing on this topic as I purchased a vehicle that had strict dealer service including coolant flushes as early as 40K for heater core problem.
I agree that there must/might have been some contamination issue. Oil cooler perhaps?

oilhammer · Oct 6, 2014

Correct, you purchased it [well] used. Don't assume "dealer serviced" automatically means "correctly serviced". Because I can assure you, that is not necessarily the case.

fenne · Oct 14, 2014

I flushed the heater core several times on my wife's car. Last time I did I used CLR. Then I noticed the temp gauge wasn't showing operating temp....over 100*F outside with the AC on and temp gauge was below 190*F. Put a new thermostat in when doing the timing belt....heater works great!

jjcsnlynn · Oct 26, 2014

oilhammer said:
Yep, that's why it happens. The B5's heater core seems to have little tolerance for foreign coolants contaminating and mudding up the system.

I've had pretty good success flushing them out, though. It may take a few times, and a garden hose, but I've never had to replace one because of this.

Do you flush them in both directions or just back flush?

peiphil · Oct 26, 2014

Back flush first most important!
Use a pail, pump and clr and put a screen under the return hose to the pail.
When your done that you can flush both ways with just water.
Also have to stress how important it is to use distilled water in your new coolant mix.
River water would be better than tap water in a pinch!

oilhammer · Oct 27, 2014

I go both ways.

Antsrcool · Oct 27, 2014

I use this it works every time http://www.streetsideauto.com/p/per...SZO8XN5ulMCN1AO5a4OUFuqO-FPECAkzwFxoCpO7w_wcB

It even fixes the fords when there cookant turns to a battery.

jjcsnlynn · Oct 28, 2014

Unfortunatly, I have a very faint coolant smell in cabin. If I flush it, especially if I use a cleaner or CLR, I expect I'll get a big leak.

I should probably change it.

vwztips · Nov 6, 2014

Antsrcool said:
I use this it works every time http://www.streetsideauto.com/p/per...SZO8XN5ulMCN1AO5a4OUFuqO-FPECAkzwFxoCpO7w_wcB

It even fixes the fords when there cookant turns to a battery.

I have used CLR with some success. Thought I would try this stuf. Picked up a bottle this moring and it states on the bottle do not use with aluminum engines or cooling systems. Most cooling systems I have seen use aluminum radiators.

Any issues with eating up the heater core?

Heater Core Plugged 2005 Passat TDI

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