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Aluminum thermostat housing upgrade: affects temp gauge?
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Vanagon Nut
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PostPosted: Sat Nov 08, 2014 1:48 pm    Post subject: Aluminum thermostat housing upgrade: affects temp gauge? Reply with quote

Hi folks.

I recently rebuilt most of the cooling system on my '88 Westy including installation of an aluminum thermostat housing. My temp gauge now reads higher. Who else has found that switching from plastic to aluminum housing caused the temp gauge to read higher? (or lower?) Has anyone figured out the exact cause? OEM wire corrosion? Or? This is noted in the gowesty website: http://www.gowesty.com/ec_view_details.php?id=23281&category_id=&category_parent_id=

I'm still a newb to the 2.1 cooling system so am very wary of air trapped in system and/or other issue causing engine to run too hot. My infrared gun suggests things are ok (highest temp was seen at big steel pipe at driver side head: 200º - 210º F), send return hoses to rad feel ok, rad fan eventually comes on at idle.

Assuming air is all bled out and that all parts, new or near new are ok, getting used to a higher needle position is no problem. Not knowing the exact cause just bugs me!

Thanks.
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indytriple
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PostPosted: Sat Nov 08, 2014 4:55 pm    Post subject: Reply with quote

I had this problem when I installed the GW alloy thermo housing. I had to dial my temp gauge back down a bit using their gauge calibrator. I used a infrared temp gun to verify that my gauge had indeed jumped due to the new thermo housing. It is definitely a real phenomenon.
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PostPosted: Sat Nov 08, 2014 5:02 pm    Post subject: Re: Aluminum thermostat housing upgrade: affects temp gauge? Reply with quote

I found all vanagons run hot until you completely bleed the cooling systems. Yuo may still have air in the system. If the over flow
is working correctly, heat cycling the engine a few time will fix this.


Vanagon Nut wrote:
Hi folks.

I recently rebuilt most of the cooling system on my '88 Westy including installation of an aluminum thermostat housing. My temp gauge now reads higher. Who else has found that switching from plastic to aluminum housing caused the temp gauge to read higher? (or lower?) Has anyone figured out the exact cause? OEM wire corrosion? Or? This is noted in the gowesty website: http://www.gowesty.com/ec_view_details.php?id=23281&category_id=&category_parent_id=

I'm still a newb to the 2.1 cooling system so am very wary of air trapped in system and/or other issue causing engine to run too hot. My infrared gun suggests things are ok (highest temp was seen at big steel pipe at driver side head: 200º - 210º F), send return hoses to rad feel ok, rad fan eventually comes on at idle.

Assuming air is all bled out and that all parts, new or near new are ok, getting used to a higher needle position is no problem. Not knowing the exact cause just bugs me!

Thanks.
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PostPosted: Sat Nov 08, 2014 5:33 pm    Post subject: Reply with quote

I'd have to guess the issue isn't the metal housing, it is the new temp sender for the gauge that you have to use with the metal housing.

I would be very cautious "adjusting" the gauge reading with an added resistor as there is a chance you will make it so the flashing LED in the temp gauge won't warn you when the engine over heats, or will only warn you when the engine is much hotter than with the original sender.

Mark
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Vanagon Nut
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PostPosted: Sat Nov 08, 2014 8:28 pm    Post subject: Reply with quote

Thanks guys.

The "fill" and expansion tanks (and cap) seem to be doing their job. In the past ~ 20 miles the fill tank has lowered down 2 or 3 times so far.

I wondered about differences in temp sensor but doesn't the 1.9 use the same sensor? I also thought there might be electrical differences (specs) between Syncro and 2wd Vanagon temp 1 gauges. For the gas Vanagon, Van-cafe website notes applications and vagcat.com shows different part numbers over the years but I assume this is due to the different instrument cluster faces, thus temp gauge position and style.

In light of Gowesty's article, I did wonder what I'm seeing is due to the negative side of the temp gauge circuit using different path.

Meh. No big deal. I got a bunch of new cooling parts in there.
What could possibLYE go wrong? Wink




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PostPosted: Sat Nov 08, 2014 8:52 pm    Post subject: Reply with quote

You could test the resistance values of the before and after temperature sensors under varying heat conditions to see if they are the same or if they are different.
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PostPosted: Sat Nov 08, 2014 8:59 pm    Post subject: Reply with quote

Snort wrote:
You could test the resistance values of the before and after temperature sensors under varying heat conditions to see if they are the same or if they are different.


Yes! I did similar with temp 2 sensors some years ago.
Not sure what the thread and pitch are on the Syncro temp 1 sensor though. (stem coolant loss) Don't have a spare sensor of that type.
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PostPosted: Sun Nov 09, 2014 2:32 pm    Post subject: Aluminum thermostat housing Reply with quote

Go Westy now includes their gauge recalibration kit with the purchase of their aluminum aftermarket housing for this very reason. Combination of different sensor and aluminum housing cause different readings

UPDATE: As of May 2011, all of our thermostat kits now include the GoWesty temperature gauge calibrator. We developed this device after experiencing temp gauge anomalies on some in-house installations. Theoretically, any temp gauge in a water-cooled Vanagon should read the same with any of the three types of senders VW used. However, we all know these are pretty old vehicles. In practice, we've occasionally found slight differences in coolant temp gauge readings after installing our thermostat housing kit. This is due not only to a difference in the included sensor, but also a lower electrical resistance in the whole circuit due to a nice, new all-metal thermostat housing (and the subsequent elimination of the old, corroded wire). Instructions are included to calibrate the temperature gauge (if necessary).
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PostPosted: Sun Nov 09, 2014 4:07 pm    Post subject: Reply with quote

I didn't upgrade to the GW housing, but when I rebuilt my engine, I sandblasted & powdercoated my syncro housing. After the rebuilt I had a devil of a time getting my temps reconciling with what my gauge was showing. I ended up getting an aftermarket water temp gauge, and I'm most often happily driving along at 195F.

I bought the GW recalibration kit, but haven't bothered installing it yet.


HTH!
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PostPosted: Sun Nov 09, 2014 10:42 pm    Post subject: Reply with quote

Baxta wrote:
I didn't upgrade to the GW housing, but when I rebuilt my engine, I sandblasted & powdercoated my syncro housing. After the rebuilt I had a devil of a time getting my temps reconciling with what my gauge was showing. I ended up getting an aftermarket water temp gauge, and I'm most often happily driving along at 195F.

I bought the GW recalibration kit, but haven't bothered installing it yet.


HTH!


I have the same phenomenom happen to me.

I converted a 1.9L van to a 2.1L Syncro engine, the temperature noxw reads higher. I had the housing beadblasted and I then painted it. Weird because they both use the same temperature sender...
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PostPosted: Mon Nov 10, 2014 10:52 am    Post subject: Reply with quote

ALIKA T3: that's very interesting.

Along with Gowestys comments on this, all I can figure is that the ground path via the Syncro housing, engine, ground straps, frame is a more efficient than the brown ground wire etc. from the 2.1 2wd temp 1 connector. As the graph in Bentley shows, resistance of the sensor drops as coolant temp rises. If there's less resistance in the Syncro housing ground path, that might explain things. Hard to imagine that being the case though. Then again, as GW notes, a corroded ground wire might explain the difference.

Though it would be redundant, what would happen if the OEM temp 1 ground wire were attached to the Syncro thermostat housing?
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PostPosted: Mon Nov 10, 2014 12:47 pm    Post subject: Reply with quote

Vanagon Nut wrote:
....Though it would be redundant, what would happen if the OEM temp 1 ground wire were attached to the Syncro thermostat housing?


You should NOT do that. It would create a potential fire hazard.

The notion that the GW metal housing make too good of a ground is absurd. When the vans were newer and the wiring was in good shape it had as good of a ground as it could get. While that ground may have degraded over time at most you could now have the ground back like it was when the vehicle was newer. How would that be a problem? The issue is that many of the replacement single wire temp senders are not calibrated to match the OEM single wire senders.

Also, the sender called Temp 1 is in the fuel injection system, not related to the gauge. Temp 1 measures the intake air temperature for the ECU to use in the fuel mapping. Temp 2 is engine temperature for the ECU to use. The gauge engine temp sender has no formal number and isn't 1 or 2 since those are officially taken by the fuel injection senders.

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PostPosted: Mon Nov 10, 2014 12:55 pm    Post subject: Reply with quote

FWIW, my gage reads the same now with the GW t-stat housing as it did with the OE plastic housing. I didn't need to mess with their recalibration doo-hicky at all.
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PostPosted: Mon Nov 10, 2014 7:23 pm    Post subject: Reply with quote

Thanks for those corrections Mark. Though I worded it incorrectly, I was referring to the OEM 2wd temperature gauge sensor ground.

Ok. I see now. The difference is between an OEM single wire temperature gauge sensor vs aftermarket.

Neil.
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PostPosted: Mon Nov 10, 2014 7:57 pm    Post subject: Reply with quote

Sorry, I thought you were calling it Temp 1 and reading it again that isn't clear.

When the metal housing is used it takes a single wire sender for the temp gauge while the plastic housing used a 2 wire sender since the plastic can't act as a ground. When you convert to the metal housing and single wire sender you use 1 of the 2 wires, the signal wire. The other wire that was used to ground the sender isn't needed and shouldn't be used. The reason it shouldn't is because the other end of that ground wire is screwed to the body. If you attach the sender end of the ground wire to engine metal and the other end is to the body then it becomes a 3rd engine/trans ground strap for any current that flows through the straps. Since that includes the starter and alternator circuits those currents can be substantial. If the main straps were loose, left off, or weakened in some way those high currents would try to use the small wire as their return path. That small ground wire could get hot enough to cause its insulation to catch fire and spread to adjacent wires it is routed with. Ideally the heavy main straps would always be in place with solid connections and that fire would never happen but the risk is real.

Mark
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PostPosted: Mon Nov 10, 2014 8:18 pm    Post subject: Reply with quote

crazyvwvanman wrote:


.... When you convert to the metal housing and single wire sender you use 1 of the 2 wires, the signal wire. The other wire that was used to ground the sender isn't needed and shouldn't be used. The reason it shouldn't is because the other end of that ground wire is screwed to the body. If you attach the sender end of the ground wire to engine metal and the other end is to the body then it becomes a 3rd engine/trans ground strap for any current that flows through the straps. Since that includes the starter and alternator circuits those currents can be substantial. If the main straps were loose, left off, or weakened in some way those high currents would try to use the small wire as their return path. That small ground wire could get hot enough to cause its insulation to catch fire and spread to adjacent wires it is routed with. Ideally the heavy main straps would always be in place with solid connections and that fire would never happen but the risk is real.

Mark


Ah, ok. I had already understood the former part of what you wrote above but totally get what you're saying.

I should have expressed this in my post. With GW's comment in mind, I was suggesting using the OEM ground wire in question for testing purposes not as a solution to a problem. Regardless, I did not consider possible scenarios which are potentially very real.

And as a side note, I'll be removing the wire I added between the O2 sensor body and frame.

Neil.
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PostPosted: Mon Nov 10, 2014 10:45 pm    Post subject: Reply with quote

In my case, I still use a single wire, since the van is a 1.9L and the engine+wiring harness come from a syncro.

I left the syncro sender on it, and it reads high.

I bought a new one, but I'm still dealing with broken studs in the case…so engine doesn't run yet.

I'm wondering if I should put the old sender that still on the old engine though, if the new ones are not calibrated, that sucks Evil or Very Mad
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PostPosted: Wed Feb 08, 2023 2:13 pm    Post subject: Re: Aluminum thermostat housing upgrade: affects temp gauge? Reply with quote

Reviving this thread because I took the same path as the OP and am having the same problem. I can verify temps at the engine to confirm gauge accuracy and use the adjustable resistor that GW included, but the comment above about this potentially disabling the warning light makes me take pause. And if this new housing and sender causes the temp gauge to read different, what is the other (temp2?) sensor that goes to the ECU doing? If this is also different the fuel mapping could be way off. Per a local mechanic I should watch my MPG to see if this may be the case. Silly me for replacing the plastic housing thinking it was a logical improvement.
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PostPosted: Wed Feb 08, 2023 3:55 pm    Post subject: Re: Aluminum thermostat housing upgrade: affects temp gauge? Reply with quote

I’ve seen older vw Audi plastic coolant parts fail spectacularly. My choice would be a robust cooling system that won’t leave me stranded. Metal seems a better choice.

I’m having a little problem understanding the logic. Old wiring, poor ground paths, etc add resistance that should lower the gauge reading not raise it.

As long as all the air is purged and radiator fan is cycling, that the stock gauge rides a little higher before is likely something you need to get used to. The coolant level warning light is probably the better system monitor. All things considered, loss of coolant is what causes the engine to go into melt down. The sending unit needs coolant on it to record temp. I’ve seen engines overheat because of coolant loss in some instances and the temp gauge did not indicate it till there was steam in the cooling system and the gauge pegs just before you loose power for good.
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PostPosted: Wed Feb 08, 2023 4:21 pm    Post subject: Re: Aluminum thermostat housing upgrade: affects temp gauge? Reply with quote

Don't worry, the Temp2 sensor is a 2 wire type.
It doesn't use the housing for part of the wiring like the single wire gauge sensors do.

The basic problem seems to be that the aftermarket single wire gauge senders currently available don't have the correct resistance values.

So when you buy a new aftermarket one it is probably going to read higher than the original VW ones did.

Mark

JEL91Westy wrote:
....if this new housing and sender causes the temp gauge to read different, what is the other (temp2?) sensor that goes to the ECU doing? .....
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