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How to tell if my engine is overheating?
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myvanrunsonrainbows
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PostPosted: Wed Jul 22, 2020 9:19 pm    Post subject: How to tell if my engine is overheating? Reply with quote

Hello vanagoners, new owner of a 1980 2.0L aircooled here.

I inherited this van from my grandma last year, and replaced the longblock myself with a newly rebuilt one from the Bus Depot during quarantine.

I finished about a month ago, and have put about 400 miles on the new engine.
I have had two mechanics who claim to be experienced with VWs look at it, and both told me everything seems to be running fine. That being said, the first mechanic set my timing to 20 degrees after TDC, and the second mechanic told me that he was an idiot, and moved it back to 6 degrees after TDC at 950 rpm idle.

I am concerned that my engine is running hot.
It drives fine, but the tip of my oil dipstick is too hot to hold when I remove it.
I have a temperature gun, and I typically see temps of 280-285F when I point it at the top of the heads next to the fuel injectors (the hottest part is usually the bolt that holds the air intake tubes onto the head).
On a particularly hot day, after climbing a relatively steep mountain pass, I saw 310 degrees in that same spot.

I have ordered a Dakota Digital CHT gauge, but they are back ordered due to COVID, and might not be available for another month.
My engine tin is mostly intact, except for one piece on the bottom driver side beneath the push rods.
New engine seal. Clean engine.

I'm hoping to take it on a road trip next week, but I am terrified of overheating and burning out my new engine.

Am I being too paranoid?
Is there anything else I can do to confirm if my engine is overheating?

Any advice or thoughts would be greatly appreciate.

Sincerely,
Angelo

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PostPosted: Thu Jul 23, 2020 2:23 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Cylinder head temps are ok but shuck yourself of the burden of outside help and learn to tune this yourself. What does your sticker say the timing should be?


Get stock parts in, Get a timing gun, set it up, check that it advances smoothly when revved, and worry not about who the idiot really is.
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Wildthings
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PostPosted: Thu Jul 23, 2020 3:21 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Set your timing to 28° BTDC @3800+ rpms, hoses off. If you see ambient temperatures that are frequently above 100°F you could back the timing off to 26° BTDC. If you suck on the retard nipple on the vacuum can does it hold vacuum? It is best on these old rigs to not set your timing using the book method as it does not take into account wear and incorrect parts that might have been installed over the years, especially if the retard can is bad the book method will give very poor results.

You could have someone with a broad band air/fuel ratio meter check your air fuel ratio. Is your rig a California model or a Federal model?

The end of the dipstick that is in the oil is always going to be too hot to touch if the engine is even close to normal operating temperatures. Using an IR gun if you shoot the bottom of the block along the case seam halfway between the rear of the block and the cover over the pickup screen you will get a pretty good idea of the actual oil temp. After a long highway run seeing oil temps of 230° if pretty normal.

The causes of high oil temperature and high head temperatures are different How hot was the engine when you took the above picture?

These engine regulate oil temperature by sensing oil pressure and not temperature. If you try to maintain too high an oil pressure by running an overly thick oil like 20w50 the high oil pressure will cause the oil to bypass the oil cooler until the oil gets hot enough to thin down to were the engine wants it to be. IMO you want a synthetic oil with a low first number and a moderate second number, I typically run 5w40 synthetic myself and Porsche is now recommending 0w40 for their older rigs.
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PostPosted: Thu Jul 23, 2020 9:32 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Those temps all sound fine, but yes, learn to time it yourself. If you have points how to set the dwell too. And get a timing gun that allows you to set the timing on it, much easier to be sure you've got it right.

Get all of the correct tin too! There is a reason VW had it there!

Enjoy...
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Wildthings
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PostPosted: Thu Jul 23, 2020 9:56 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

I can't see if the engine seal is there or not, but it needs to be. Can't see the ducting for your heater air either, but if it isn't there that would like leave holes for hot air to be suck up into the engine compartment making your cooling system less efficient.
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MarkWard
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PostPosted: Thu Jul 23, 2020 10:12 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

An oil temp gauge would a nice feature and might more available from JEGS or Summit Racing.

I can see the rod that controls the cooling flaps. Are you using the thermostat. Stock, if the thermostat failed, the flaps should move to the open position. That said 40 years later no telling what’s in there.
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AZ Landshaper
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PostPosted: Thu Jul 23, 2020 1:44 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Oh man. so many variable on the AC engines. Do you have any vac leaks? they wreak havoc on engine temp of an AC motor. I would trust an infrared gun and an oil temp gauge to help you make decisions.

28 BTDC at 2500 rpms is the place to be but your dwell needs to be on. If thats off the timing wont be accurate. start with compression check then correct the dwell. move to timing at 28 BTDC. then check for vac leaks and use correct oil weight.

BTW nice engine. you could eat a sandwich off that motor without staining the bread and getting that grit in your teeth.

PS not voting because its just not clear to me yet.
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myvanrunsonrainbows
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PostPosted: Thu Jul 23, 2020 4:07 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Wildthings wrote:
I can't see if the engine seal is there or not, but it needs to be. Can't see the ducting for your heater air either, but if it isn't there that would like leave holes for hot air to be suck up into the engine compartment making your cooling system less efficient.


Yes, new engine seal, and complete heater ducting. I havent taped all of my holes/edges the way I've seen some people do it, but all of the stock seals are in place.
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myvanrunsonrainbows
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PostPosted: Thu Jul 23, 2020 4:09 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

AZ Landshaper wrote:
Oh man. so many variable on the AC engines. Do you have any vac leaks? they wreak havoc on engine temp of an AC motor. I would trust an infrared gun and an oil temp gauge to help you make decisions.

28 BTDC at 2500 rpms is the place to be but your dwell needs to be on. If thats off the timing wont be accurate. start with compression check then correct the dwell. move to timing at 28 BTDC. then check for vac leaks and use correct oil weight.

BTW nice engine. you could eat a sandwich off that motor without staining the bread and getting that grit in your teeth.

PS not voting because its just not clear to me yet.


Thanks for the thorough response! I am researching how to set timing, as it is honestly still a mystery to me. Any recommendations for good "timing for dummies" resources?

I replaced all of the vacuum lines, and havent noticed any leaks. Whats the best way to check?
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myvanrunsonrainbows
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PostPosted: Thu Jul 23, 2020 4:10 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

MarkWard wrote:
An oil temp gauge would a nice feature and might more available from JEGS or Summit Racing.

I can see the rod that controls the cooling flaps. Are you using the thermostat. Stock, if the thermostat failed, the flaps should move to the open position. That said 40 years later no telling what’s in there.


My thermomstat is shot (leaked out all the fluid), but the flaps are stuck in the "open/cooling" position. I know its not ideal, but I am currently looking for a new thermostat spring.

Yeah, I'm looking into oil temp gauges. Seems like I need to drill and tap the plate on the bottom of the engine to install it?

Any recommendations on a particular sender + gauge combo?

Thanks for the response!
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myvanrunsonrainbows
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PostPosted: Thu Jul 23, 2020 4:19 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Thank you everyone for the responses. Here's my big question that hasnt been answered yet.

Other than a CHT or oil gauge, is there any way to check if my van is overheating using a infrared gun, or any other readily available tool?

I have a laundry list of improvements I want to make, but I'm trying to answer the short term question of "can I take this on a 300 mile road trip next week??"

Thank you all!

P.S.
Check out what I found inside my old heat exchanger (since replaced)

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MarkWard
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PostPosted: Thu Jul 23, 2020 6:28 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Someone told me many years ago, if you drip spit on to the case, if it steams off, it’s running hot.
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wcdennis
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PostPosted: Thu Jul 23, 2020 6:29 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

I’m afraid to ask what that is. It looks like something from a horror movie.
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Wildthings
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PostPosted: Thu Jul 23, 2020 6:54 pm    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Pelican Parts sells a Taco Plate that is set up for an oil temperature sensor and a cover to keep the wiring and sensor from being damaged as easily. The plate under the oil pickup screen is not a good place to read the oil temps as there is little oil flow between the screen and the plate so a lot of cooling can occur leading to significantly lower oil temperature readings.

As I said you can get a pretty good oil temperature reading be shooting the case about 1/2 way between the rear of the engine and the cover under the oil pickup screen with an IR gun

It doesn't look like in your photo that the flaps are quite all the way open, the little lever where the cable attaches should be vertical when the engine is hot.

Is your rig a Federal or California model and do you have to pass smog where you live? Does your retard can hold vacuum?
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myvanrunsonrainbows
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PostPosted: Sat Jul 25, 2020 8:55 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Wildthings wrote:
Pelican Parts sells a Taco Plate that is set up for an oil temperature sensor and a cover to keep the wiring and sensor from being damaged as easily. The plate under the oil pickup screen is not a good place to read the oil temps as there is little oil flow between the screen and the plate so a lot of cooling can occur leading to significantly lower oil temperature readings.


Is that where the Taco Plate installs? is it worthwhile?

Wildthings wrote:
As I said you can get a pretty good oil temperature reading be shooting the case about 1/2 way between the rear of the engine and the cover under the oil pickup screen with an IR gun


I'll check that today. What temperature range should I be looking for there?

Wildthings wrote:
It doesn't look like in your photo that the flaps are quite all the way open, the little lever where the cable attaches should be vertical when the engine is hot.


I'll double check that... I think this pic was from before I disabled my thermometer

Wildthings wrote:
Is your rig a Federal or California model and do you have to pass smog where you live?


Yes, it's a california model, and it already passed smog. The smog guy said it passed with flying colors.

Wildthings wrote:
Does your retard can hold vacuum?


No idea. How do I test this?

Thanks for your response!
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myvanrunsonrainbows
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PostPosted: Sat Jul 25, 2020 9:02 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

wcdennis wrote:
I’m afraid to ask what that is. It looks like something from a horror movie.


That was the inside of my passenger side heat exchanger.
This van was my grandmas before she gave it to me, and about a year before the engine gave out, she complained that her heater stopped working.

It looks like oil was leaking out of the heads, and draining into the heat exchanger, where it eventually caught fire and melted the aluminum fins inside.
It's amazing that it didn't damage anything else or catch the van on fire...

New engine and heat exchangers in now.
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PostPosted: Sat Jul 25, 2020 9:10 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Or it was running with too much timing and a too lean a mixture. 1500F and you will melt aluminum.
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Wildthings
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PostPosted: Sat Jul 25, 2020 9:35 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

myvanrunsonrainbows wrote:
Wildthings wrote:
Pelican Parts sells a Taco Plate that is set up for an oil temperature sensor and a cover to keep the wiring and sensor from being damaged as easily. The plate under the oil pickup screen is not a good place to read the oil temps as there is little oil flow between the screen and the plate so a lot of cooling can occur leading to significantly lower oil temperature readings.


Is that where the Taco Plate installs? is it worthwhile?


The Taco Plate is the 2.5" diameter round plate under the right rear of the engine held on by the two small screws.

Quote:
Wildthings wrote:
As I said you can get a pretty good oil temperature reading by shooting the case about 1/2 way between the rear of the engine and the cover under the oil pickup screen with an IR gun


I'll check that today. What temperature range should I be looking for there?


After a long highway run at 65mph you want to see something in the 210-230° range. This can vary a lot though. VW posted some numbers and I believe they were higher, but don't remember.

Quote:
Wildthings wrote:
It doesn't look like in your photo that the flaps are quite all the way open, the little lever where the cable attaches should be vertical when the engine is hot.


I'll double check that... I think this pic was from before I disabled my thermometer

Wildthings wrote:
Is your rig a Federal or California model and do you have to pass smog where you live?


Yes, it's a california model, and it already passed smog. The smog guy said it passed with flying colors.


The sounds good, but puts you on the lean side which could run the head temps up noticeably.

Quote:
Wildthings wrote:
Does your retard can hold vacuum?


No idea. How do I test this?


The retard nipple is the nipple on the vacuum can that points towards the distributor body. Just put a tight fitting hose on it and suck on the other end. Once you draw vacuum on it, you can then seal the end of the hose off with your tongue. It should hold vacuum until you remove your tongue from the end of the hose. You could also use a vacuum pump if you have one available.

Quote:
Thanks for your response!
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myvanrunsonrainbows
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PostPosted: Mon Jul 27, 2020 9:59 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

Took her on a test trip this weekend. Climbed a mountain pass, and got out to check my engine temp (bottom of engine) multiple times.
Highest temp I saw was 240 after the steepest part of the grade. Most of the drive it stayed in the 210-220 range.
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Wildthings
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PostPosted: Mon Jul 27, 2020 10:13 am    Post subject: Re: How to tell if my engine is overheating? Reply with quote

I would think those oil temps would be just fine. Run synthetic oil if you are concerned about the effects of the heat on the oil.
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