Volkswagen Passat Forum banner

141 - 160 of 176 Posts

·
Registered
Joined
·
1,606 Posts
This is strange, but I guess possible. The lack of coolant return flow would force more coolant through the oil cooler, but once the thermostat opens, there should be plenty of flow as it then could bypass the heater core through the radiator. Perhaps that would require higher rpm to get enough flow.
Absolutely correct !!!, in this (OP,s) case his pump is being "starved" restricted in the amount of coolant available to be pumped ,and has become "a snake chasing it's tail". Not enough available coolant to suction side of pump,thus not enough on the pressure side of pump to push coolant thru engine, then thru heater core, to supply suction side of pump (area by inside of thermostat where line #2 in diagram also returns)...BUT should be getting supplemental coolant as PZ has pointed out thru oil cooler into return line #2 to aid in the pump's supply of available coolant, but I NOW believe IT is also clogged, as was/is heater core, since it is just as if not more a labyrinth of nooks and crannys. For the effort and frustration you have went through sorting this out, I would replace it now before final coolant fill. A quick check by, as your fore mentioned trumpet playing (ha) would confirm this, but I'm betting it is clogged.
 

·
Registered
Joined
·
179 Posts
Discussion Starter #142
Absolutely correct !!!, in this (OP,s) case his pump is being "starved" restricted in the amount of coolant available to be pumped ,and has become "a snake chasing it's tail". Not enough available coolant to suction side of pump,thus not enough on the pressure side of pump to push coolant thru engine, then thru heater core, to supply suction side of pump (area by inside of thermostat where line #2 in diagram also returns)...BUT should be getting supplemental coolant as PZ has pointed out thru oil cooler into return line #2 to aid in the pump's supply of available coolant, but I NOW believe IT is also clogged, as was/is heater core, since it is just as if not more a labyrinth of nooks and crannys. For the effort and frustration you have went through sorting this out, I would replace it now before final coolant fill. A quick check by, as your fore mentioned trumpet playing (ha) would confirm this, but I'm betting it is clogged.
You think my oil cooler is clogged? I picked up one off a junkyard car the other day just in case. I suppose I could check that.
 

·
Registered
Joined
·
1,606 Posts
I would be willing to bet it is restricted, if not clogged to the level that your heater core was, this do to its flow rate and hose size, kudos to PZ for this insight, as in the diagram of coolant flow, it is a subtle "footnote" for lack of a better term, I had somewhat overlooked as just being ancillary. Also if possible repost your pic of your broken PCV elbow as in that pic one can clearly see (in lower left quadrant) where coolant pipe #2 enters engine block/coolant housing,its flow directly pushing across thermostat actuation bulb, this explains why thermostat is installed with its "bridge" vertical to reduce any eddy turbulence, insuring clean flow, will post in this thread excerpt from Bentley later today.
 

·
Registered
Joined
·
179 Posts
Discussion Starter #144
I
I would be willing to bet it is restricted, if not clogged to the level that your heater core was, this do to its flow rate and hose size, kudos to PZ for this insight, as in the diagram of coolant flow, it is a subtle "footnote" for lack of a better term, I had somewhat overlooked as just being ancillary. Also if possible repost your pic of your broken PCV elbow as in that pic one can clearly see (in lower left quadrant) where coolant pipe #2 enters engine block/coolant housing,its flow directly pushing across thermostat actuation bulb, this explains why thermostat is installed with its "bridge" vertical to reduce any eddy turbulence, insuring clean flow, will post in this thread excerpt from Bentley later today.
I can say with absolute certainty that it's not clogged. Or if it was it definitely isn't now. I took the hoses off and blew into them. No restrictions there.
 

·
Registered
Joined
·
350 Posts
Replacing the heater core is a big job, IIRC you'll need a second person to help disconnect the dash and pull it out. I've seen it done on youtube but never personally. Before you do that I'd just like to remind you of what I mentioned earlier: I flushed my heater core with air and water, and I guess the pulsations created turbulence to move out the grit. I don't want to be a broken record but I suggest do that before attempting a heater core swap. Just because you have heat with the heater core it may still be plugged.

I don't suppose you live near Westchester, NY by chance? You could borrow my flush gun and the hoses. I have the cheap $60 manual one and not the gates one which auto pulsates like a machine gun, probably more effective.
 

·
Registered
Joined
·
179 Posts
Discussion Starter #146
Once I get the brakes sorted, I want to drive it around for a few miles with the heater hoses reversed like they are now. that may even help loosen a little more gunk. Then when I go to bypass it again, I will try your suggestion. I am not hopeful because I have flushed it over and over again but it won't hurt to try one more time.

No, I'm all the way down in Maryland.
 

·
Registered
Joined
·
179 Posts
Discussion Starter #147
Ran the car the other day with the heater core backwards. It still got hotter than I'd like. About 225F. BUT I believe I saw the thermostat open for a couple minutes, so there's hope.
 

·
Registered
Joined
·
338 Posts
if you get the a fill and flush kit (its cheap) you can add one of these to it if you have a source of air:
 

·
Registered
Joined
·
338 Posts
Easiest spot is in one of the two heater hoses going to the core by the battery.
What I actually did was grabbed a piece of heater hose from a junk yard, went and found a barbed PVC fitting that fit it, and then a PVC fitting that was threaded for hose thread. This was attached to the outlet of the heater core. I used a short piece of hose that went to a gated y (just a y with the valves, im sure you know what I am talking about) and one side of that y was water, the other side was air, so I could just send whatever through the system without having to run around.

does that make sense?
 

·
Registered
Joined
·
179 Posts
Discussion Starter #151
Finally drove the car. Heater core in reverse. Hovered around 224F. Peaked at 228F. 6 miles. I couldn't go a half mile before without overheating almost immediately. I still think I need to change the heater core but I'll flush it after I drive it a bit and see what I can get out of it.
 

·
Registered
Joined
·
26,644 Posts
If you have someone to help you, the quicker way of changing the heater core takes about 4 hours or so depending on your experience level. I've done it once and it was much faster than taking everything apart (I've done that 3 times).
 

·
Registered
Joined
·
179 Posts
Discussion Starter #153
So I flushed the heater core one more time and got a bunch of crud out. Homes everything back up and finally put coolant in. Went on a nice drive today. Still a bit hot but bearable. Around 220F or lower. Then it jumped up to about 232F and I got a STOP on the dash with an oil pressure light.

Pulled over and turned the car off. Checked the oil and looked around the engine. Nothing seemed amiss. Then it drove back 5 miles with no similar issue.

Any ideas what could have happened?
 

·
Registered
Joined
·
179 Posts
Discussion Starter #155
Thank you. I'll look into the Bentley. Wonder if they have an iPad version.

Thanks for the diagrams. No codes, no weird Moses. But I did notice the few times it happened when the light went away the temperature dropped significantly.

I'm going to pick up a oil pressure switch and a pressure tester.
 

·
Registered
Joined
·
350 Posts
There's a bentley cd but don't be fooled it's so old it basically doesn't work on any recent OS. If you buy it I think they may give you access to the web version as a workaround, as long as you give them your serial number. You'd have to ask them but I've heard of people doing that successfully. I would've bought the CD if it actually worked on any recent laptop. The lowest price for the books on eBay is between $50 to $100 and the CD is about the same.
 

·
Registered
Joined
·
1,606 Posts
Hey, I agree about the two volume set I have a single volume, it is like working with a mattress from a baby crib, They are a 100 bucks at ECS.......but I am sure you can find them cheaper........I like to be able to easily copy, mark on pages, bookmark pages with index cards so I can flip back and forth.....and see clearly (large print), but best investment I made torwards my Passats
 

·
Registered
Joined
·
350 Posts
Boydage with a W8 recently said that he pressure tested his coolant system and discovered it wouldn't hold pressure, and that was the cause of his heater blowing cold. In his case the o-ring on the cap was bad, but in general the cap could be bad. The coolant kits I think replace the cap for the test but if you tap into the reservoir return you could probably test the cap as well.

Also PZ recently said a bad battery caused the oil pressure light to trigger on his son's car so you may want to check your battery as well.
 

·
Registered
Joined
·
179 Posts
Discussion Starter #160
It holds a nice vacuum every time I bleed it so there's no leak, and the reservoir is new so the cap is good.

The battery is tested and good.

Good thoughts though
 
141 - 160 of 176 Posts
Top