Have a question on oil temp sitting in traffic for over an hour

[blues90]

I drove to Costco Sat a 6 mile one way drive . The ambient temp was 97 F. On there the oil temp based on my VDO oil pressure and oil temps gauges it read 181 F . On the way back there was a parade so I was stuck in traffic for over an hour all that time was spent just crawling. I have a 73 t-3 Square back auto trans. After a while the oil temp was near 220F and the oil light would come on unless I placed it in neutral. On top of the 97 ambient there was all the heat of two lanes of bumper to bumper traffic generated by the other cars plus the blacktop heat rising up plus the auto trans cooling on the converter blowing at the engine . Once I finally got on a road that was not blocked off and moving 35 to 40 mph the temps soon dropped down to 190F the oil light stayed off. I only drove 4 miles at 35 to 40 MPH not long enough to bring the temps down to the 180F it usually reads.

Thee next day I checked the oil and it was 1 pint low because it leaks at the rear main seal. I always check it and add a pint so not to get below the middle .

I've never been stuck in traffic this long in such high heat.

I've had this happen on a long freeway run on a hot day and the oil light would come on.

My thinking is the cooling fan at idle is not moving a lot of air and at a low fan speed. The fan does all the work including the oil cooler needs air flow to do its job. I started it the next day drove a mile round trip sounded and ran the same and it was 1 pm and already 91F . On start up the oil pressure was 50 PSI the oil temp below the 120 mark . After the mile drive the oil pressure was 40 PSI and oil temp about 135 F . It sounded and drove the same as before. I realize VDO gauges are not dead on accurate , I just have them as a base to see if anything reads out of the norm. I've been using Valvoline SAE 40 the racing oil with the zinc. The VDO oil sender read pressure and activates the oil light yet the one I have turns the light on @ 8PSI the gauge was reading about the same.

The engine has all the proper tin in place and a working thermostat and the flaps open fully. I have the Empi header with the heat exchange and the fan has the flex pipes forcing air through the exchangers the heat works.

I get an engine with a load generates heat yet the fan is moving more air.

Anyone have any thoughts, opinions , had this happen?

I know VW didn't use gauges for a reason Russ always brought this up.

[Erik G]

[KTPhil]

220 is a MINIMUM and not a sign of overheating. It is necessary to boil off water from condensation and anything less will not do that.

I also have an overheating problem, as many know, from my broken distributor on the return for the Invasion five years ago. 260-280 is too hot, and that’s how mine runs on the freeway (or higher, it was still climbing!), so the engine is now out and stripped for another rebuild.

I also have learned a lot about viscosity and the operation of the dual-relief case plungers. Thicker oil may boost pressure, but it will “look” like thick cold oil and the plunger will bypass the oil cooler, making it run hotter, not cooler. 20-50 is thinner when cold (when it doesn't need the cooler anyway), but it stays a little too thick when hot and so the cooler may be bypassed.

I ran this oil for years without trouble, but I was probably shortening the life of the motor. Live and learn.

If yours is running hot, check the timing… not just static, but also the eventual advance at higher rpm and vacuum. That’s how mine failed. Broken spring posts or weights meant it never stopped increasing with rpm… right up to 45 degrees mechanical advance!

Part of the reason monograde oil is recommended for VWs is this behavior of the cooler bypass plunger.

[Max Welton]

Looks like normal ops for the conditions you describe.

Max
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[blues90]

I checked to make certain the bellows was fine and the thermostat was fine and the flex tubes to the HE . everything was fine. About a year ago I changed the mounts because I had a lot of vibration in drive . I had 2 good used ones that were not cracked or collapsed so I put those in. Once I did I changed the oil with the exact amount required 5.3 pints. I had to make a new mark the engine was raised up so the new mark is 5/16" below the original . I just wanted to make sure , I doubt 5 /16" makes much difference. I would think that when new the original mark should have lined up with the proper amount of oil.

I wanted to see so I added 4 oz of oil and it now is on the new mark so I was not a pint low as I thought.

I still want to at least pull the oil cooler bypass valve to see if it moves free and install the new sender in that spot . I imagine they are free , heck the original 73 was so full of gunk with a plugged filter screen they came out easy.

Once the new proper drain plug arrives I will change the oil and install the new sender after checking the relief valve . I was going to check the oil control valve as well I got the hex head type screw in caps and have new crush washers . I have 2 new pistons yet only new springs the the cooler bypass valve . I imagine the old springs may be fine since they might be a bit weaker allowing the pistons to move sooner. All I can do is compare the length of the new to the old . Some use a scale to see what the compressed length reads . Just want to be sure the cooler bypass is not sticking . Do notice a bit of wet oil by the cooler seals , don't know how much pressure the cooler can take the cooler in not leaking and the seals are 20 years old they are the proper ones the cooler and case have the larger 10mm ports. Oil isn't pouring out it just takes time to see some wet oil . At this point I'm not about to pull the engine and replace them . I have a new orange crank seal just need the socket . Since it's FI engine it's a lot of work and I already spent 5 days 2 years ago replacing the FI head gaskets because it needed new runner boots and fuel lines and and vacuum lines . I did it once engine in the car in 1985 yet I was not almost 73 back then . I did the runner boots in engine in the car. I just check the oil don't drive more than 350 miles per year the leaks have not become any worse so I have time if I have to dig into that , I hope not . One big leak was the sump plate so I fixed that , it was always wet not any more , i never over tighten the nuts just use a nut driver in a cross pattern and a 10 mm socket. No idea how the plates holes got that way. That thing is so thick can't imagine the holes were high at the top.

[KTPhil]

I worked up a jig using threaded rods, washers, nuts, and a digital luggage scale to validate my spring lengths under load. The scale was a cheapie from Amazon, the rest of the hardware came from the local ACE.

[blues90]

I don't find much info on VDO oil temp sensors. I have one in the sump plate in place of the drain plug and I got one to fit the cooler pressure bypass relief plug. VDO sent me a chart showing what the gauge should read based on ohms , I connected a variable pot to the disconnected oil temp wire at the sensor and the gauge read what it should. I asked what the room temp resistance on the sensor should read and was told they are not calibrated that way. On one site I found 700 ohm and it reads very near this. The one in the sump reads 120 ohm higher and both are for the 300 F temp gauge so I would think they should read the same. The gauges are not linear so you can't place a resistor in parallel probably why the space between the gauge marks get wider apart from 120 F to 300 F . I don't expect the gauges to read accurate , I just use them to see if there is a sudden change form what they normally read which is 180F , no idea what the actual temp is.

All I can find is using the one in the relief valve some say it's the best spot , others say there is no real oil flow past the piston even if it's not bypassing the cooler and state you are basically reading case temps. That does make sense to me.

As far as the relief valve springs I've read they don't go bad and others say they become weak and loose their tension from years of heat which makes sense.

I do what to check that piston and spring and do have 2 NOS springs and one new NOS piston. I just what to make sure that piston is moving free then see how much different the old springs length is compared to the new ones. May as well install the VDO oil temp sensor in the so I can at least compare the readings between the one in the sump.

Also in the Bentley the compressed length of the springs very 1 3/4" 12.3-16 lb, that's close to a 4 lb difference. It's dual relief case.