Another HIGH OIL TEMP Issue - Troubleshooting, any new ideas?

[disrepos]

I have been having an issue I'd never seen before for a while now, but after spending tons of time and replacing 1 part at a time, I am stumped. Here's what's up:

2002 allroad, 6-speed. Car runs and acts fine driving for about half an hour of driving. During that time, the oil temp slowly moves up from nothing to around 230*. Prior to this, it would settle there. Now, though, it just continues to rise. Freeway, idle, city, doesn't matter. It continues to rise, and around 245*, my coolant temp starts creeping up as well. So have I have:
Replaced oil temp sensor
Replaced oil cooler
Replaced coolant temp sensor
Replaced cooling fan switch and controller (cooling fans work as they should now)
Piggie pipes
Tuned and run on e85 to see if it would run cooler
Verified stock tune runs at correct AFR
Flushed and replaced coolant (several times)
Flushed and replaced oil (0-40 synthetic (twice)
Switched to high capacity oil filter
Replaced water pump and thermostat, verified timing (twice)
Waited until winter to see if anything changed or got better

....And I still have the same issue. Car is fine for about a half an hour after starting cold. Oil temp creeps to 245 or so, then oil and coolant temps rise together until I shut the car down. I've only allowed it to go a hair above the first bar to the right of normal operation.

A couple other details:
Oil is the color of oil
Coolant is the color of coolant
Exhaust looks and smells normal
No air bubbles or other anomalies in coolant or oil (One theory is that the head gasket might be blown in a particular spot which forces hot gases into oil only)

I'm stuck. Beyond replacing or rebuilding the motor, I can't think of any other possibilities. Maybe try replacing the radiator, but I don't see how there would be an issue this would help.

Any ideas? I may have forgot to mention a couple things as well.

[jbain2]

Are you pulling the temp values from VCDS, I’m assuming?


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[disrepos]

In addition, I verified that the coolant lines to and from the oil cooler flow freely.

A thought this summer was to add an additional oil cooler via thermostatic sandwich plate at oil filter, mocal air cooled oil cooler, but that has not taken place yet.

[disrepos]

Are you pulling the temp values from VCDS, I’m assuming?


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Verified in VAG that oil temp appears to lead water temp.

Also, just additional details: No codes any issues in VAG over this last year. New primary O2s, all LTFTs within +/- 2.

Heater core is starting to clog up. Bled twice since noticing the climate control fan isn't blowing as hot as it should now that it's winter.

One thought is that perhaps this vehicle has had Prestone type coolant mixed in at some point so over all cooling system efficiency is down.

[Fahrvergnugen]

Definitely sounds like cooling system blockage to me

[rollerton]

Definitely sounds like cooling system blockage to me

Could be....but having a hard time picturing coolant system clogging causing the OIL TEMP to creep up before the coolant?
Not a common thing. Would it be worth installing a cheap oil temp gauge temporarily to verify what you're seeing?

[4xaudi]

I would say radiator I had the exact same problem last spring. If you cut the end caps off the bottom third is all crapped up. I had done a couple flushes before I replaced it finally.

[disrepos]

I would say radiator I had the exact same problem last spring. If you cut the end caps off the bottom third is all crapped up. I had done a couple flushes before I replaced it finally.

This will be the next item replaced. Thanks. Found many threads with these issues, but none that found solutions.

[PaperToast]

I would say radiator I had the exact same problem last spring. If you cut the end caps off the bottom third is all crapped up. I had done a couple flushes before I replaced it finally.

i'll +1 this
given the age of the car, radiator replacement is due
when i had my 3rd TB done at 230k, the rad (which was original) was starting to leak at the ends
got a new one due to the shop dropping the water pump on the old one

[Bordom]

I have a stock Allroad rad if interested.

[Fahrvergnugen]

Could be....but having a hard time picturing coolant system clogging causing the OIL TEMP to creep up before the coolant?
Not a common thing. Would it be worth installing a cheap oil temp gauge temporarily to verify what you're seeing?

From post 4, "Heater core is starting to clog up. Bled twice since noticing the climate control fan isn't blowing as hot as it should now that it's winter.

One thought is that perhaps this vehicle has had Prestone type coolant mixed in at some point so over all cooling system efficiency is down. "


Anytime one part of the cooling system is starting to clog, you'd have to bet that it is happening elsewhere, or is about to happen.

[4xaudi]

Could be....but having a hard time picturing coolant system clogging causing the OIL TEMP to creep up before the coolant?
Not a common thing. Would it be worth installing a cheap oil temp gauge temporarily to verify what you're seeing?

That was my first observation the oil temp would start to creep up especially under load. Then the coolant temp would start creeping up after the oil temp was up 25-35C higher than normal(225C).

[rollerton]

From post 4, "Heater core is starting to clog up. Bled twice since noticing the climate control fan isn't blowing as hot as it should now that it's winter.

One thought is that perhaps this vehicle has had Prestone type coolant mixed in at some point so over all cooling system efficiency is down. "


Anytime one part of the cooling system is starting to clog, you'd have to bet that it is happening elsewhere, or is about to happen.

Good theory..except the heater core is a 'bypass' type thing, it has absolutely nothing to do with actual cooling of the system. It does sort of provide some extra heat dissipation when on full heat and fan blowing...but it is not designed to aid in cooling the engine in general. It can be entirely plugged or removed and you shouldn't notice any difference in cooling.

[disrepos]

Good theory..except the heater core is a 'bypass' type thing, it has absolutely nothing to do with actual cooling of the system. It does sort of provide some extra heat dissipation when on full heat and fan blowing...but it is not designed to aid in cooling the engine in general. It can be entirely plugged or removed and you shouldn't notice any difference in cooling.

I am replacing my heater core this week. Was so glad to find out there is an access point on the driver side next to the accelerator - should be too hard. If it helps noticeably with the oil temp on my ride, it seems like a sure thing that the radiator is the final solution to the puzzle.

Doing research on this issue, it seems quite common. There are many posts across the net of owners of B5 and C5 vehicles with unusually high oil temps. I haven't searched for other platforms. I suspect adding Prestone to G12 or perhaps some specific types of coolant flush is the cause. I've seen several cars completely flushed then run on Prestone for years without issue, so I don't think its the green stuff alone. Nor does mileage nor age alone seem to be at fault. Most cars never have any issues whatsoever even after 200-250k miles, but to those that have problems, those problems aren't mild and this is happening at much lower mileage: 75k, 100k etc. I could be completely wrong, but there has to be some commonality.

[disrepos]

I would say radiator I had the exact same problem last spring. If you cut the end caps off the bottom third is all crapped up. I had done a couple flushes before I replaced it finally.

Did you post a thread on this? I think it was your thread that got me more focused on the cooling system.

[rollerton]

The theory might work...it could cure your whole problem...I'm just trying to understand how or whats behind it. Theoretically you could test it by just plumbing the heater core hoses together to bypass it. If you still have the oil temp curiosity after that then it wasn't the heater core?
By design the heater core CAN NOT increase coolant temps and therefore oil temp. I mean...how can it?

[chris86vw]

The theory might work...it could cure your whole problem...I'm just trying to understand how or whats behind it. Theoretically you could test it by just plumbing the heater core hoses together to bypass it. If you still have the oil temp curiosity after that then it wasn't the heater core?
By design the heater core CAN NOT increase coolant temps and therefore oil temp. I mean...how can it?

I'm with you on this. According to the first post oil temp goes up and then coolant follows. If this was a problem created by lack of cooling as in heater core was blocked or similar problem removing it from the loop and reducing the capacity/cooling ability of it then I would think it would be a plausible cause. But the problem doesn't seem to stem from an issue with the cooling system based on the oil temp rising before coolant temp, then again the gauges are dumb so coolant may actually be high before he notices the gauge.

OP have you checked vcds data blocks and seen which occurs first or just relying on the cluster?



I don't know what it is, but I'm not sure a heater core is going to help simply because it doesn't add all that much to the cooling system.



Is this 12:1 engine in the sig what is in the car or something else?

[AllroadCorbin]

I bet that pan sensor is on its way out. They die often and unless it’s OEM or maybe hella they die quicker / don’t even work right


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[C5S6]

Looks like you are in Boise - Have you met Iancu AKA "kinderutz"? I'm sure he'd be glad to give you a 2nd opinion. https://www.yelp.com/biz/the-audi-guy-boise

[disrepos]

Looks like you are in Boise - Have you met Iancu AKA "kinderutz"? I'm sure he'd be glad to give you a 2nd opinion. https://www.yelp.com/biz/the-audi-guy-boise

I have not met him in person, but he is in our local audi forum giving out diagnostic advice from time to time. I think the issue is solved, just need to put in the work.

[disrepos]

The theory might work...it could cure your whole problem...I'm just trying to understand how or whats behind it. Theoretically you could test it by just plumbing the heater core hoses together to bypass it. If you still have the oil temp curiosity after that then it wasn't the heater core?
By design the heater core CAN NOT increase coolant temps and therefore oil temp. I mean...how can it?

The heater core is a side issue that needs to be fixed. When I replaced the oil cooler, it helped with oil temp some, but also made the coolant temp more dependent on oil temp. Then since the heat core was also having issues, it really made me start leaning toward a flow issue with the cooling system. I have a vagcom, verified oil temp is driving coolant temp. This wasn't really neccessary, because its easy to see the coolant temp warm up to normal operating level a few minutes after start up. As we all know, oil temp takes much longer. I could watch it heat up 150, 175, 200, 225.... and around 235, coolant temp starts moving up from the center bar. YEAH.... this was messing with me a lot. I've never seen anything like it.

Manual transmission allroads have coolant cooled transmission oil coolers as well, so to complicate things more, there was the possibility of something going on with that as well.

regarding the 12:1 motor, I ended up selling it and installing to a friend's car. Just forgot to update my sig. We dropped it to 11:1 with comp lowering headgaskets as we decided it was a little too extreme. That car runs great, spunky as hell even off boost.

[disrepos]

Replaced radiator - completely solved the oil temp issue as well as the rising coolant temp issue due to oil temp.

Now runs at around 210-215 degrees around town and just under 225 on the freeway slight uphill at 80pmh.

A friend also suggested that the issue, especially being common, could have stemmed from using tap water with coolant instead of distilled. At this point, whether it was mixing the wrong coolant or tap water or something else, replacing all the heat exchanging components fixed it. I went with a mid-range radiator with a 1.33" core. There were some cheaper ones out there but they had 1.25" cores ($75-$140). OEM radiators were around $500. I just couldn't bring myself to pay that.

[chris86vw]

Glad you got that sorted

Size difference sounds about what my measurements were for the auto/allroad manual radiator vs just a6 manual radiator which didn't have any trans cooler stuff.

[Fahrvergnugen]

The theory might work...it could cure your whole problem...I'm just trying to understand how or whats behind it. Theoretically you could test it by just plumbing the heater core hoses together to bypass it. If you still have the oil temp curiosity after that then it wasn't the heater core?
By design the heater core CAN NOT increase coolant temps and therefore oil temp. I mean...how can it?

If you read all of what I wrote, I said that if one section is clogged, there are others. And from what I can tell, sounds like I was right (with the radiator replacement curing it).

[rollerton]

If you read all of what I wrote, I said that if one section is clogged, there are others. And from what I can tell, sounds like I was right (with the radiator replacement curing it).

I know, I understand the point of what you said- but from a really basic engineering point of view, how would the coolant NOT heat up prior to the oil if the cooling system is clogged?
if the efficiency of the cooling system is compromised wouldn't that show in higher coolant temps prior to higher oil temps? I mean- the OIL has to get the heat from somewhere; lots of it is byproduct of thermal conduction just from the combustion through the metal of the engine. But..and I'm not arguing- it really seems like the problem got fixed- but how does the oil get seemingly heated up abnormally fast by coolant that is is warming up at what seems like normal rate? If the coolant temp indicates normal, where is the oil getting the heat? Thermal conduction?
At what point / where in the system is the compromised cooling system heating up the oil; and if so how is the coolant NOT overheating before the oil temps creep?
I like that it's fixed and seems like a reasonable conclusion to come to...but the physics of it leave me scratching my head.

[Fahrvergnugen]

I understand, and agree; I was just going off the idea that the cooling system had to be compromised elsewhere. As for How this worked, I haven't a clue either. Been dicking with cars for 30 years, but these particular cars still have quite a few mysteries... I've learned when there is one weird thing, start there and Hope for the best; hopefully that makes sense...

Speaking of, I'm going to refresh a mysterious thread I've had going on for some time...