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Thu Jun 16, 2022 6:51 pm

Moderator note:
Linking these two together, locking the newest one .....

https://www.thesamba.com/vw/forum/viewtopic.php?t=770384

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With regaurds to the cooling system have replaced

thermostat 3 times
Thermostat housing
Sendor at thermostat 3times
Sensor at radiator
Cooling fan switch
Radiator

My fan low speed only comes on sometimes? Bad ground affecting fan switch?

Ok so heres the story I'll spare you all the trials and tribulations basically all listed above is in attempts to rectify a faulty cooling system. I might be dealing with a combo of things love some help.

When I drive at 20 and below it overheats fast. Sometimes it doesnt over heat. Sometimes the fans medium mode comes on sometimes only high. Sometimes it seems like fan doesnt come on at all. Unless I was lied too by my trusted mechanic whom has allways seemed to shoot me strait he replaced the fan switch I think it may be a ground but thier more.

I have had the van for 13yrs and have allways had a bypass at rear heater photo below I was thinking I might try and shorten the connection tube inside the bypass because it causes some pinching of the hose not completely when I took of one of the clasps I used my screwdriver to pry some crud tension on the still connected hoses and it hissed. First thing I thought was ok " air in the line" I'm getting a miss reading and my van hasent been over heating. But it was bled raised in front ect ect.

Can air be slowly building back up in the system somehow? And is thier a good place to inspect to right that? I have had a front lever in the front heater that has become stuck aswell this seems to have caused the van to overheat as it may seem faster. The lever goes side to side but wips back to the middle I suspect a faulty valve or cable. Also without car movement and fan off it seems to blow hot. I'm pretty well versed in the syndrome for such airflow past radiator but it seems the heater blowing ideas?. Furthermore running the heater does nothing to bring back suspected overheat. I am at my with end and want to be careful not to fry my beloved wasserboxer

Thu Jun 16, 2022 8:10 pm

If you're relying on the gauge to tell you it is overheating I would get a second opinion from an IR temp gun.

Adventurewagon36 wrote: ...Can air be slowly building back up in the system somehow?...

Yes. One way that 'air' gets in the cooling system is if combustion gases are getting past the gasket in the head. This appears as air in the pressurized tank (which should be totally full under all conditions).

Thu Jun 16, 2022 8:34 pm

Still learning the samba forum interface my apologies in advance

Thu Jun 16, 2022 8:44 pm

Thank you for reply. Great input! . But wouldn't persay explain the overheating yes? I have never thought it could be combustion gas getting past the head. Is thier a non invasive way to test this? I have 30k on a new motor full rebuild. Is thier any other way air could be in the system? Perhaps the bleed process wasent proper. I was only told of it by my mechanic. If one of the valves wasent opened perhaps they didnt get all air out? If the van got too hot at some point it would warp the head slightly causing this prematurely?am I right thinking this? Any inquiry is greatly appreciated. If I am dealing with this as the culprit would the solution be to take off head and have it tested? If this is simply air from a faulty bleed. **Would a failed toggle/heater valve @front heater cause over heating? Or perhaps a partially clogged front heater core ?**

Thu Jun 16, 2022 9:40 pm

most likely bad head gasket. you can rent a chemical testing kit from your local FLAPS (Friendly Local Autp Parts Store) google test head gasket

in theory air could get in from a loose hose or something when it cools it sucks air in but you would more likely see a coolant drip as well

Thu Jun 16, 2022 9:43 pm

Adventurewagon36 wrote: ...I have had the van for 13yrs and have allways had a bypass at rear heater photo below I was thinking I might try and shorten the connection tube inside the bypass because it causes some pinching of the hose not completely when I took of one of the clasps I used my screwdriver to pry some crud tension on the still connected hoses and it hissed...

When the rear heater is removed, those two hoses should be PLUGGED, NOT connected as an open loop like you show. That loop just bypasses the radiator. When the heater is in place, it dissipates the heat in the coolant. With the heater removed, the open loop just reduces the effectiveness of your cooling system and makes it more likely that you will overheat.

That alone probably isn't enough to cause overheating unless other parts of the system are marginal, but it sure isn't helping anything.

Thu Jun 16, 2022 9:48 pm

Work on the bleeding of the system first, find a technique that you are capable of performing on your own and eliminate the air from the system.

Looks like the system has been opened a number of times to replace parts, let’s make sure you start without air in the system and see what symptoms return.

Thu Jun 16, 2022 10:08 pm

Very good to know about the bypass. I heard someone on the samba claim if the bypass was even pinched or would cause overheating? I wouldn't of suspected plugging either end? I shall explore this further and probably do just that as a precaution. The idea of a head gasket being most likely with 30k miles? Wouldn't thier be a leak if that were the case? I was going to buy go westy fancy cooling system pressurization pump kit. Probably go ahead and make a libby bong and if all seems well with the pressurization pump kit. I will try and give it proper fil up open valve at the engine compartment and see if once filled appropriately it will cool as it should. Does this seem proper in my logic?

***I must ask!!!!*** am I clear in thinking that if you have air in the line it affects the flow of coolant which can cause inconsistent cooling system. So your engine can overheat because of lack of flow to radiator. Thus random high fan only syndrome skipping medium speed. and your gauge can misread because of air also. If this is the case typical culprits ,expansion cap, exhaust leak head,vacume n cooldown at a hose point?

I have about $25k invested in my 1987 adventure wagon and ot has truly become a labor of love. I want resolve in worste way. I have learned much over the years thanks to the samba and the long road of owning a vanagon. So nice to be able to have some support besides mechanics. !!Thank you for your help!!

Thu Jun 16, 2022 10:24 pm

if you have owned it 13 years and have 25k in it, that's what, 1900/year

you're doing better than most

i would either add or properly delete the rear heater mess and do a full and proper bleed on the cooling system.

but as pointed out it may be wise to buy a coolant CO tester before going any further.

also laser around where the temp sensor is on the engine. i can tell you with 100% certainty that when the temp gauge is just a hair above the LED in the gauge (like 1/2 the width of the needle) it's at 190* in a stock setup

Thu Jun 16, 2022 10:27 pm

Adventurewagon36 wrote: The idea of a head gasket being most likely with 30k miles? Wouldn't thier be a leak if that were the case?

no. head gasket failure for your symptoms is combustion air getting into coolant not coolant leaking. It a $10, 10 minute test that can be mostly* conclusive. way faster and easier diagnostics than other approaches. PS, head gasket failure does not depend on mileage.

It is rare but possible that the head gasket leaks in conditions other than the test allows for - like high load high RPM. this is very rare.

do the test

Fri Jun 17, 2022 1:56 am

Since it doesn't sound like you ever intend to hook the rear heater back up then replacing the 5/8 x 1/2 tees in the heater hoses underneath the body with 5/8" connectors, thus eliminating the bypass or plugs inside make sense to do. You will need to seal off the holes in the body if you do this to keep mice out. I bought the best quality 5/8" connectors my local NAPA could find in their system and not the cheaper ones they had in stock.

Also if you have a 1985 or earlier van your overheating could just be the coolant being low in the expansion (pressure) tank, this will trigger the coolant warning light and cause the gauge to read high.

With a stock thermostat and a stock fan switch the fan will not come on very often at all, unless the vehicle sits idling for an extended time. If you buy and install a 75° fan switch (25195948175) the fan will come on much quicker and more often.

If after having taken a drive without shutting off the engine, if you open the engine compartment lid and view the expansion tank, is it full to the top with no more than a tiny bubble? If it is not full to the top you need to figure out why. Your refill tank needs to be filled to the lower line when the engine is cool.

Fri Jun 17, 2022 3:23 am

Take the rear heater hose loop out of the mix. Remove the T connectors and just go with straight barbed connectors. That loop may not be contributing a lot to your issue, but if you're never going back with the rear heater installed simplify the coolant hoses.

Your radiator fan issue might be related to the radiator resistor going bad. It's that long green worm looking thing behind the front grill and left headlight bucket. If the green insulation is cracked or cracking it might be time to replace.

Coolant issues are typically a pain to sort out in these vans. Don't know if you still have the original plastic coolant pressure tank, or have switched to a metal tank. If you still have the original plastic you might have a crack or two in it.

Fri Jun 17, 2022 4:09 am

Let's back up here.

What year is your Van?

What engine is in your Van?

What transmission is in your Van.

Do you have Air Conditioning?
Does it work?

What cooling system work have you ever had done?

When the engine was rebuilt, who did it and did they require additional cooling system repairs at the time?

Let us know what you have, we can then be better able to help for every cooling system is not the same design.

Dave

Fri Jun 17, 2022 8:25 am

Lots of good info already posted. One additional thought to consider is that I view water pumps to be wear items and have ended up replacing them one or more times on almost every vehicle I've owned.

Fri Jun 17, 2022 8:54 am

Run it to operating temp then park it nose down to cool. Any air will collect in the expansion tank. Top it up as required.

Fri Jun 17, 2022 9:33 am

1987
2.1 waterboxer
Vanagon adventure wagon

*New block motor to replace the old 30k ago by a shop specializing in these motors. Cant recall name off hand
* new transmission full rebuild 3k ago

""Cooling system work done"
New radiator
New thermostat housing
New thermostat replaced multiple times to resolve issue
New sender @ housing also replaced 2 times
New sensor at radiator
New fan switch at radiator "old one failed"

Per this correspondence! Thank you for all your help support and Time!!
I will bypass properly rear heater !!
I will do a compression test!!
I will test cap and pressure for leaks with" go westy tool"
I will idle till hot let cool inverted tail end up to check for bubbles and air top off./ or libby bong and bleed
I'll repeat the test for bubbles after libby bong procedure

I will update this group with results asap.
Thankyou very much guys!!

Fri Jun 17, 2022 10:02 am

Here is a thread where, with assistance from various Samba members, I was able to diagnose and repair a situation where neither cooling fan was working in my vanagon:

https://www.thesamba.com/vw/forum/viewtopic.php?t=680389&highlight=

Fri Jun 17, 2022 11:51 am

Adventurewagon36 wrote:

That's not an Adventurewagen.

Fri Jun 17, 2022 1:44 pm

Can you explain to us why you say it is overheating?

Does the tank behind the license plate get overfilled for no apparent reason?

Does the coolant level in the tank in the engine area drop after running and it has cooled off?

Dave

Fri Jun 17, 2022 6:32 pm

My armchair guess with your symptoms is a water pump impeller that is sometimes slipping on its drive shaft.

BK