High oil temp and forensic engine investigation

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satchmo
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High oil temp and forensic engine investigation

Post by satchmo » Sun Jun 17, 2012 10:15 am

I'm working on a 78 Westy that is pretty much stock except it has gauges for oil pressure, oil temperature and CHT installed. There is a slight leak from either the oil cooler seals or the oil cooler itself (and before anyone says it, yes, I already checked the oil pressure sender for leaks).

The engine runs great except once the oil temp hits 180 F or so on the freeway (60-65 mph, 3600 rpm, 70 degrees ambient temp, fairly level grade, no wind), the oil temp just keeps rising; rapidly in fact. After 10 minutes or less, it is at 250 F and I shut her down to cool off. I have verified the oil temp with an infrared gun at the sump. It matches what the gauge says. During this time, the oil pressure drops off a little (expected with hot oil) and the CHT temps stay rock solid at 350-375. If I drive on surface streets (once the engine has cooled down a bit) at a maximum speed of 45 mph, the oil temp stays at 210-220. If never cools off with slower speed or on a downhill. I find this disconcerting.

So take a look at this photo of the oil cooler area:

Image


My first question is why is the heater tube bashed in like that? There is also a dent in the end of the oil cooler that is hard to see. The dents look like they were caused by an object rubbing there with considerable pressure and repetition rather than being hit by something. Does this have anything to do with the oil overheating problem? I know the gasket between the tin and the top of the oil cooler is missing, but I don't think it would have this much effect on oil temp.

So, the oil gets too hot. I don't believe there is too much heat being produced since it takes quite a while for the engine to get to 180, even at freeway speeds. A thermostat is installed and the flaps are working fine, but it does seem odd that the oil starts to heat up about the time the flaps open. I would think that if the air flow from the cooling fan was really poor, then I would see pretty high CHTs too. But I don't. I suppose there could be a mouse nest on top of the oil cooler (found out earlier that the cabin heater tubes were completely blocked by mouse nests), but it looks clear in the photo. My only other guess is that the oil cooler is plugged/non-functional, or that the oil relief valve is stuck in a position that is shunting oil away from the oil cooler.

I have a new oil cooler that I will be installing this week. New oil cooler seals and a new gasket for the top of the cooler will also be installed. Let me know if you have any other amazing ideas or insights. Also, try to come up with an explanation for the dents on the heater tube and oil cooler. The 78 originally had an EGR filter close to this area. Do you suppose if the EGR filter was loose and flapping around here it might have caused this?

Thanks, Tim
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First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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RSorak 71Westy
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Re: High oil temp and forensic engine investigation

Post by RSorak 71Westy » Sun Jun 17, 2012 11:46 am

What weight oil are you running? and what is the oil pressure at speed? If the pressure is over 40 lbs or so the oil maybe never seeing the cooler, because the VW engines oiling system is designed to bypass the cooler is the oil pressure is above 40 or so. The cure is to run thinner oil to lower the pressure. I recently switched from 10W40 to 10W30 on my bus for just this reason and my oil is now running cooler at speed than it ever has. I had a problem very similar to yours that any highway speed driving would drive the oil to 225 plus.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

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satchmo
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Re: High oil temp and forensic engine investigation

Post by satchmo » Sun Jun 17, 2012 1:04 pm

RSorak 71Westy wrote:What weight oil are you running? and what is the oil pressure at speed? If the pressure is over 40 lbs or so the oil maybe never seeing the cooler, because the VW engines oiling system is designed to bypass the cooler is the oil pressure is above 40 or so. The cure is to run thinner oil to lower the pressure. I recently switched from 10W40 to 10W30 on my bus for just this reason and my oil is now running cooler at speed than it ever has. I had a problem very similar to yours that any highway speed driving would drive the oil to 225 plus.
It is 20-50 Brad Penn Oil and pressure is around 40 psi at highway speed until the oil gets hot, then it starts to go down. That lower pressure when the oil is hot should, in theory, open up the passage to the oil cooler, and oil temp and pressure should stabilize. Unless the oil pressure relief piston is stuck in oil-cooler bypass mode. If that is the case, then it is like running without an oil cooler and the engine will just get hotter no matter what the pressure is - until the oil is smoking and the bearings are spinning.

I find it kind of hard to believe that VW designed the engine to burn itself up by bypassing the oil cooler if the oil pressure was too good. Most of us shoot for 10 psi of oil pressure per 1000 rpm as a lower limit. I thought the oil cooler bypass/pressure relief piston was there to make sure you didn't blow out the oil cooler during cold weather starts when the oil is thicker than honey, not to prevent oil circulation to the cooler when the engine has excellent oil pressure. Aren't the cooling flaps are the primary means of adjustment for the amount of oil cooling that takes place rather than the amount of oil circulating to the cooler?

Tim
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First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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RSorak 71Westy
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Re: High oil temp and forensic engine investigation

Post by RSorak 71Westy » Sun Jun 17, 2012 2:10 pm

cooler bypass/pressure relief piston
There are 2 pistons not 1, 1 is the cooler bypass piston and it bypass' the cooler at any pressure above about 40 under the assumption that cold oil is thick oil.

The pressure relief piston just does that job only. If the pressure goes above x it dumps oil back to the sump.

This is the way it is.....if your engine is stock. Since your VW engine shouldn't run extended periods above 4000 RPM you shouldn't need oil pressure above 40.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

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Re: High oil temp and forensic engine investigation

Post by SlowLane » Sun Jun 17, 2012 2:23 pm

satchmo wrote: I know the gasket between the tin and the top of the oil cooler is missing, but I don't think it would have this much effect on oil temp.
I'm going to respectfully disagree with you here, sir. It's the pressure differential between the top and bottom of the cooler that forces air through it, not the velocity of the air being blown at the top of the cooler. The missing seal is allowing the pressure to leak out around the sides of the cooler. Think of it as the type IV equivalent to the infamous "Hoover Bit" on a type 1.
RSorak wrote:There are 2 pistons not 1, 1 is the cooler bypass piston and it bypass' the cooler at any pressure above about 40 under the assumption that cold oil is thick oil.
The type IV engine only has the one piston, which serves the dual purpose of pressure relief and cooler bypassing, unlike the later "dual-relief" type 1 engines.

An interesting additional feature of the type IV case is that it has an internal oil passage which routes the dumped oil from the relief valve directly back to the oil pump inlet. Presumably this improves oil delivery to the pump, since it doesn't have to draw as much from the sump.
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satchmo
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Re: High oil temp and forensic engine investigation

Post by satchmo » Sun Jun 17, 2012 2:53 pm

SlowLane wrote:
satchmo wrote: I know the gasket between the tin and the top of the oil cooler is missing, but I don't think it would have this much effect on oil temp.
I'm going to respectfully disagree with you here, sir. It's the pressure differential between the top and bottom of the cooler that forces air through it, not the velocity of the air being blown at the top of the cooler. The missing seal is allowing the pressure to leak out around the sides of the cooler. Think of it as the type IV equivalent to the infamous "Hoover Bit" on a type 1.
RSorak wrote:There are 2 pistons not 1, 1 is the cooler bypass piston and it bypass' the cooler at any pressure above about 40 under the assumption that cold oil is thick oil.
The type IV engine only has the one piston, which serves the dual purpose of pressure relief and cooler bypassing, unlike the later "dual-relief" type 1 engines.

An interesting additional feature of the type IV case is that it has an internal oil passage which routes the dumped oil from the relief valve directly back to the oil pump inlet. Presumably this improves oil delivery to the pump, since it doesn't have to draw as much from the sump.
I can see that the missing gasket on top of the oil cooler will diminish air flow through the cooler. Just didn't think its absence would have such a profound effect, like in the amount I am seeing. Many engines are missing this gasket because it is supposedly NLA. This situation will be remedied soon.

Also, I thought there were two oil relief valves in a type IV case: the one on the bottom of the case with the single slot cap, and one on the side between and below cylinders 1 and 2 (could be between 3 and 4 - it has been a while since I looked at a bare case) with a triple square cap.

Anyway, are we saying that there is NO flow through the oil cooler when pressure is above 40 psi?

Tim
By three methods we may learn wisdom:
First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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RSorak 71Westy
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Re: High oil temp and forensic engine investigation

Post by RSorak 71Westy » Sun Jun 17, 2012 3:20 pm

Anyway, are we saying that there is NO flow through the oil cooler when pressure is above 40 psi?
YES !!!
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

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satchmo
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Re: High oil temp and forensic engine investigation

Post by satchmo » Sun Jun 17, 2012 4:25 pm

RSorak 71Westy wrote:
Anyway, are we saying that there is NO flow through the oil cooler when pressure is above 40 psi?
YES !!!
OK!

Here is a picture of the engine case on my 73 bus. It has a second oil pressure valve under cylinder #1. I don't know if all type 4 cases have this or not. I'm thinking it was a CB case.

Image

Tim
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second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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Re: High oil temp and forensic engine investigation

Post by Hippie » Sun Jun 17, 2012 6:26 pm

satchmo wrote:Image
That looks melted more than bashed.
Image

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SlowLane
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Re: High oil temp and forensic engine investigation

Post by SlowLane » Sun Jun 17, 2012 6:38 pm

satchmo wrote: Here is a picture of the engine case on my 73 bus. It has a second oil pressure valve under cylinder #1. I don't know if all type 4 cases have this or not. I'm thinking it was a CB case.

Image
Hmm, ok, I stand corrected. I only had my Vanagon engine and Bentley to go by. So sometime between 1973 and 1981 the second oil pressure relief valve was apparently dropped. You'll have to look to see if it's there on this '78 or not, if it matters.

The other thought I had was that the dented-in end of that oil cooler could be partially occluding flow through the cooler. I'm not certain, but I think the oil flows down to the end of the cooler and back again.
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satchmo
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Re: High oil temp and forensic engine investigation

Post by satchmo » Mon Jun 18, 2012 9:10 am

SlowLane wrote:
satchmo wrote: Here is a picture of the engine case on my 73 bus. It has a second oil pressure valve under cylinder #1. I don't know if all type 4 cases have this or not. I'm thinking it was a CB case.

Image
Hmm, ok, I stand corrected. I only had my Vanagon engine and Bentley to go by. So sometime between 1973 and 1981 the second oil pressure relief valve was apparently dropped. You'll have to look to see if it's there on this '78 or not, if it matters.

The other thought I had was that the dented-in end of that oil cooler could be partially occluding flow through the cooler. I'm not certain, but I think the oil flows down to the end of the cooler and back again.
Regarding the number of pressure relief valves, Richard Atwell's FAQ states that the solid lifter case had two valves and the hydraulic case only had one (not counting the pressure relief valve at the oil filter in both). So you were wrong in that you thought you might be wrong but you were really right. :cyclopsani:

Tim
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First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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Re: High oil temp and forensic engine investigation

Post by Gypsie » Mon Jun 18, 2012 9:45 am

I am in the "no gasket around the oil cooler is not allowing it to function at it's optimum" camp.


I also note that the "Heat dump" is right there afore the valve cover sending a steady stream of hot air right across the cooler. (it is summer and you are likely redirecting all your heat right back out that tube, no?)

the crushed (melted?) heat tube could be contributing to a turbulence zone that is contributing to the all over ineffectiveness of your oil cooling circuit.

a la shin bone connected to the knee bone

It is all one magnificent power producing heat reducing jamboree of metal and oil....

I wonder if some good ol' fashioned insulation strip (something with a firm foam, or rubber, with as high a temp rating you can find) and thick enough to be squeezed between the cooler and tin, could be stuck neatly to the ultra clean tin or the top of the oil cooler to create the seal needed for this NLA part?
So it all started when I wanted to get better gas mileage....

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Re: High oil temp and forensic engine investigation

Post by vdubyah73 » Mon Jun 18, 2012 2:08 pm

get some sticky closed cell weatherstrip at hardware store. comes in different widths and thickness'. you can layer it, or use it like tape. i did.
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satchmo
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Re: High oil temp and forensic engine investigation

Post by satchmo » Mon Jun 18, 2012 3:53 pm

Thanks. I believe I have an oem gasket that I will be putting in when I change out the oil cooler.

Tim
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and third, by experience, which is bitterest. -Confucius

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Re: High oil temp and forensic engine investigation

Post by SlowLane » Tue Jun 19, 2012 10:22 am

Tim, if you have the time and inclination, can I suggest an experiment?

Before you dig into the motor and replace the cooler and its gasket, do a quick oil change to 10W30 and see if the high temperature problem persists. Then do the oil cooler swap / gasket install and see how much of an improvement you get.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
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