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      I know this has been hashed to death but I can’t find anything mentioned on the forum about this so I am going to ask. Tonight I took my car for about a 10 mile ride, it was about 85 degrees. I have no accurate temp gauge just the one that came with my VS. At the end of the drive the needle was barely above the low end block and just starting to go into the line that runs from cold to hot. I have installed a dipstick sensor that is supposed to light the oil light when the oil temp goes above 225 or so I thought. When I got home, I shut the car off and after about 5 minutes I looked at the dipstick sensor and it was fairly close to making contact to light the overtemp light.

     What I am wondering is how much do the air cooled VW engines heat soak after you shut them off and the fan stops cooling?  I do have a 190 degree fan switch and the fan was not running when I pulled into the garage. I should have looked at the dash gauge to see if it had climbed when I looked at the overtemp sensor. I’m sure the car is not running hot, I’m just trying to get an idea where the oil temp actually is without an accurate gauge. I am fairly certain that the fan switch is accurate.  Thanks.

2013 VS azure blue 2110cc

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When you've just got back from a ride and you've pushed it enough that the engine should be reasonably hot, run around the back, open the lid and touch the fan shroud (or even better, alternator); if it's hot enough that you can't hold your hand on it very long, or you can't hold on to the dip stick then you know it's up there. If a drop or 2 of water (or spit) sizzles when it hits the engine case- it's hot, and you need better instrumentation (and maybe start thinking of ways to get the underhood temps down).

If not- you're doing something right, and if we ever meet I'm going to examine your car from 1 end to the other!

You can test either an analog or digital for reasonable accuracy by sticking the probe into a cup of boiling water and see how close it comes to 212º.

regular temps:

180º - 210º Normal, happy engine

210º - 220º   Way upper Normal,  back off on hills a bit

220º - 230º  Whoa!  Pull over to let it cool and find out why it runs hot when you get home and fix it.

Over 230º    Don't drive it til it cools off.

I have never tested my engine for Heat Soak after running for a while, but that sounds like an interesting experiment.  Not sure it would cause me to change anything, though.

Last edited by Gordon Nichols

Oil temps are (partly) rpm related, and when talking about high oil temps most automatically think "cool the oil", slap an oil cooler on the engine, and quite often this seems to cure the issue. This is treating the effect (or symptom), though, when one should be looking at what's causing the problem. Think of it as continually putting a cream on a rash that itches (which, don't get me wrong, is certainly beneficial) but not looking at what's causing the itch to begin with?

I know most of you guys have heard me rant on this before, but one of the causes of high oil temps (after ascertaining that the engine combo will live on street gas, all the under the engine sheet metal is there and it's tuned properly) is not enough airflow into the engine compartment. We build these things to make 2, 3, and even close to 4 times the power output of the original 1600 cc engine with no upgrade to the cooling system, stuff it into a restrictive space that is barely adequate for the 50 something horsepower stocker. The  bigger engine now revs substantially higher (the fan using more air), the carbs consuming huge amounts of air (44IDF's will use 6-8 times the air a stock Solex 34-3 is capable of) and you have to wonder "where is all that air coming from? And the bigger question is "what happens when there's not enough air"?

With the varying rpm's and small loads imposed upon the engine when toodling around town, most of these cars seem to run fine, but have you noticed that when you jump on the highway the oil temps start to climb? If the car runs cooler on the highway on warmer days with the engine lid (even slightly) ajar there are a couple of ways to check on what's going on, one being the aquarium tubing test. Anchor 1 end of some aquarium air tube (10 feet is only a couple of dollars at the hardware store) to the middle of the fan shroud, and with someone in the passenger seat with the other end of the tube in a  glass of water, start the car and let it idle while sitting still with the engine lid up. Note the water level in the tubing. What happens when you close the engine lid? Driving around town and out on the highway? How high does the water climb in the tube? Is there a water level difference moving with the engine lid open vs being closed? Does rpm affect the water level when on the highway? What happens when a piece of 2 or 3" flexible hose is used to direct air from under the car toward the firewall hole (I'd really love to hear the results of this one!)?

I first read about the aquarium tube test on the Samba. He eventually removed the over-the-bellhousing breastplate (you can't do a hole in the firewall because there's no space between the engine and passenger compartments in a Beetle like our cars) and found a huge improvement in the driveability in his 11 second street car during the summer months (iIrc he was from Utah). The gentleman also mounted a remote thermometer in the engine compartment and found that with the engine getting closer to the amount of air it needed, under hood temps dropped significantly and the engine kept it's tune (and made closer to optimal power)  more of the time.

Time to start the morning routine- have a great day everybody (and yeah, I know, for you easterners the day is almost half over already!) Al

PS- I thought Gordon's temperature description was pretty good!

 

Last edited by ALB

Good Job Al !  A crude manometer is what you described.  Very good !  If you took a 3' length of that tubing and stapled it to a narrow board in a "U" shape so that 18" was on each side...  Glue a 12"to 18" ruler on the board between the two vertical legs of tubing...you have a manometer.  Put enough water in it so the water level is right at the 6"  or 9" increments on both sides and you can read vacuum or pressure in the engine compartment. This configuration will read up to 18" H20. More than enough to discover a problem in the engine compartment.

My engine compartment currently has a 1.5" negative pressure (vacuum) which I will soon be eliminating with modifications to the "rain guard" under the rear deck grill. The deck grill IS adequate for air flow into the engine compartment but that restrictive "rain guard" is miserably inadequate.  I have a VS, 2110/dual 44s, no hole in the firewall and a totally sealed engine compartment. Some of you read my last thread posted last Jan 6 called "Rear deck lid air intake project, Part 1. I haven't forgot about this. I just haven't had the time to get on it and do Part 2 but dialog like this prompts me to start. After the SLO Event it looks like I will have the time.

Even with the 1.5" negative pressure my car does not run hot but then I have not had it up in the mountains, on hills, at sustained speeds, on really hot days. I do know that here, down in the flatlands of SoCal on blistering days, it doesn't run hot. Some of you will remember that at one time I was simultaneously reading oil temps from 6 different places on the engine plus ambient in the engine compartment and outside while driving and idling.  Fun and interesting stuff......Hot Too !  

By the way. How many badges can we put on the deck lid grille before we get a restriction ?? I don't know but I will soon. It's on my list of things to play with after I eliminate the "rain guard" restriction. Whatever mods I do I will make them available to all of you on here.

Frank....... I know what you have on your car after many of our dialogs. I don't think you have a heat issue. I do think you need to reconstruct what you did that day and do a closer check on the latent heat issue you brought up. I would like to know that as well.  Maybe do a graph with temp on the left and elapsed time on the bottom. Heck...even duct taping a thermometer inside the engine compartment would give you some useful info. Also finding a sending unit that deflects your temp gauge a little more would help. Mine is the same as yours and I never liked how low it reads. Maybe someone here has a suggestion for a different sender...........Bruce

aircooled posted:

Good Job Al !  A crude manometer is what you described.  Very good !  If you took a 3' length of that tubing and stapled it to a narrow board in a "U" shape so that 18" was on each side...  Glue a 12"to 18" ruler on the board between the two vertical legs of tubing...you have a manometer.  Put enough water in it so the water level is right at the 6"  or 9" increments on both sides and you can read vacuum or pressure in the engine compartment. This configuration will read up to 18" H20. More than enough to discover a problem in the engine compartment.

My engine compartment currently has a 1.5" negative pressure (vacuum) which I will soon be eliminating with modifications to the "rain guard" under the rear deck grill. The deck grill IS adequate for air flow into the engine compartment but that restrictive "rain guard" is miserably inadequate.  I have a VS, 2110/dual 44s, no hole in the firewall and a totally sealed engine compartment. Some of you read my last thread posted last Jan 6 called "Rear deck lid air intake project, Part 1. I haven't forgot about this. I just haven't had the time to get on it and do Part 2 but dialog like this prompts me to start. After the SLO Event it looks like I will have the time.

Even with the 1.5" negative pressure my car does not run hot but then I have not had it up in the mountains, on hills, at sustained speeds, on really hot days. I do know that here, down in the flatlands of SoCal on blistering days, it doesn't run hot. Some of you will remember that at one time I was simultaneously reading oil temps from 6 different places on the engine plus ambient in the engine compartment and outside while driving and idling.  Fun and interesting stuff......Hot Too !  

By the way. How many badges can we put on the deck lid grille before we get a restriction ?? I don't know but I will soon. It's on my list of things to play with after I eliminate the "rain guard" restriction. Whatever mods I do I will make them available to all of you on here.

Frank....... I know what you have on your car after many of our dialogs. I don't think you have a heat issue. I do think you need to reconstruct what you did that day and do a closer check on the latent heat issue you brought up. I would like to know that as well.  Maybe do a graph with temp on the left and elapsed time on the bottom. Heck...even duct taping a thermometer inside the engine compartment would give you some useful info. Also finding a sending unit that deflects your temp gauge a little more would help. Mine is the same as yours and I never liked how low it reads. Maybe someone here has a suggestion for a different sender...........Bruce

I thought a Manometer was one guy standing on each side of a hot chick and whichever dude she went to was the better looking dude.

Frank,

As an alternative, you could "tune" your temp gauge by moving the range up or down to where you want it using your existing sender.  I did that on mine because I'm OCD and wanted the needle to be straight up at 200F.

All it takes is a suitable 1/2 watt resistor from the sender terminal, either on the sender or from the sender tab on the back of the gauge, to ground.  It may take a little trial and error to get the range the way you want it, but it's pretty easy to do and then, by calibrating everything with a dipstick thermometer, you'll know better what's going on.   For when my son drives it I added a small, stick-on red marker on the gauge glass that basically says; "Don't go higher than THIS!"

Gordon....I got a good laugh about what you do for your son. Years ago, in my case, a big boxing glove that pops out of the horn button, hits him in the face, and has "look at the gauges" printed on it would have been appropriate for my son.

The resistor you speak of, how many ohms would you suggest to start with. It's times like this that I miss Radio Shack.

 What's nice is that my gauges just pop out by hand since it's only that "O" Ring that holds them in place and there's enough slack in the wiring to get the gauge out far enough to do this procedure.......Bruce  

Resistor color code, including tolerance.  There’s also “Batman bl_ws Robin on yonder Gotham bridge,  Very good, will get Superman next.”  IIRC it’s black (0), brown (1), red (2), orange (3), yellow (4), green (5), blue (6), violet (7), ?? (8), white (9), gold (1%), silver (5%), nothing (10%).  It might be off by one but I’m too lazy to check and retype on an iPhone.

Oh, for crying out loud......   I never learned ANY of those silly things.  I just bought a 3-wheeled, resistor color band identifier from Radio Shack to tell me what to use.  In fact, I still have it (but it’s getting a little long in the tooth after 60 years!)

But then, I always tell people I don’t have to be an true Engineer because I married one, instead (the first female Electrical Engineer graduated from the Worcester Polytechnic Institute).

Last edited by Gordon Nichols

So Gordon let me get this right, you took a 220 ohm resistor and hooked one end to the sender terminal on the back of the gauge and grounded the other end?  That would put it in parallel not series and would bleed off current from the sender. You are actually reducing the resistance of the sender which should deflect the meter more correct?  It sounds like a great idea because as Bruce said the gauge doesn’t move much.

Yup, that's pretty much it.  Resistor in parallel with the sender, both to ground.  It's just easier to mount it up at the gauge.

All you're doing is moving the range of needle movement around to where it makes sense to YOU.  In my case, normal summer temp (200º F ) drives the needle straight up.  More to the right of straight up and I start to worry.

Last edited by Gordon Nichols

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