Oil in Coolant 1KZTE

[astr]

I have a 2003 Prado with a 1KZTE diesel and manual transmission. I find oil in the overflow reservoir floating on the coolant. I changed the oil and filter and there was no sign of coolant in the oil. I had the oil cooler replaced but not the oil cooler cover. Problem persists. Engine runs fine, no power loss or roughness. No bubbles visible when I remove the radiator cap. No engine overheating, temp gauge reads normal.

I'm leaning towards either a bad head gasket or the oil cooler cover being bad. Has anyone experienced this problem? Any suggestions based on actual experience with this engine?

 

[Eurasiaoverland]

Was there a problem identified with the oil cooler you removed? How were the gasket surfaces on the oil cooler cover (where it mates with the cooler)?

If there was a confirmed leak from the oil cooler before, it may be residual oil in the coolant, or an ongoing leak if the oil cooler cover was not properly inspected/cleaned.

If not the above, a cracked cylinder head.

 

[astr]

Was there a problem identified with the oil cooler you removed? How were the gasket surfaces on the oil cooler cover (where it mates with the cooler)?

If there was a confirmed leak from the oil cooler before, it may be residual oil in the coolant, or an ongoing leak if the oil cooler cover was not properly inspected/cleaned.

If not the above, a cracked cylinder head.

Unfortunately, I did not have the tools available to perform the work myself so had to rely on a highly regarded mechanic. I could not find a leak in the removed oil cooler but then I had no means to pressure test it. I just filled it with gasoline and let it set. No gasoline leaked out.

I had hoped that the oil in the coolant was residual but after a week of daily cleaning out the reservoir, the quantity of oil did not diminish. When doing the repair, the mechanic stated that the oil cooler cover did not need to be replaced. I don't know what his basis for this assessment was. All new Toyota gaskets were used for the repair.

I'm hoping it is not a cracked head.

 

[astr]

Update: Both the oil cooler cover and the oil cooler plate heat exchanger were replaced. The head was removed, gasket surface was resurfaced and the head tested for leaks - none found. All new gaskets were used including genuine Toyota head gasket. Still the problem persists. Any suggestions?

 

[OM617YOTA]

Can the water cooled turbo leak oil into the coolant?

If it was an auto trans, I'd be confirming the trans cooler built into the radiator hadn't failed and was leaking transmission fluid into the coolant.

Best of luck, this is a head scratcher.

 

[astr]

Can the water cooled turbo leak oil into the coolant?

If it was an auto trans, I'd be confirming the trans cooler built into the radiator hadn't failed and was leaking transmission fluid into the coolant.

Best of luck, this is a head scratcher.

Manual transmission so no oil cooler in the radiator. I was also thinking turbocharger as it has high pressure oil and coolant running to it. How to verify without replacing it?

 

[OM617YOTA]

No clue on checking the turbo for coolant leaks into the oil. Best of luck there, following this thread with interest.

 

[Greg_B]

Manual transmission so no oil cooler in the radiator. I was also thinking turbocharger as it has high pressure oil and coolant running to it. How to verify without replacing it?

CT26 on the 1KZTE?

You can disconnect and block or loop the coolant lines to and from the turbo then run it for a bit to see if that makes a difference. While there is some debate as discussed in this thread, no matter which camp you're in I would think you would be fine for the amount of time you would need to see. Sounds like its pretty apparent and quickly? Just don't run run it hard and shut down right away. Do some googling and make sure you're okay with doing it.

Is your coolant level dropping at all? If so an oil sample will tell you if there is glycol and/or water in the oil, even if you can not see any.

hth's
gb

 

[astr]

Good idea. For many years turbos ran with only oil so that might work.

 

[Eurasiaoverland]

Depending on access, you could also remove the water pipes from the turbo, look if there are signs of oil ingress. Run it for a minute or so with the pipes off and look in the coolant cavity for any signs of oil.

 

[dmjay]

Bypassing the turbo coolant lines would be my suggestion as well. You would only need to run it at idle for a few minutes to see signs of oil leaking into the cooling passages.

 

[Dougal]

Update: Both the oil cooler cover and the oil cooler plate heat exchanger were replaced. The head was removed, gasket surface was resurfaced and the head tested for leaks - none found. All new gaskets were used including genuine Toyota head gasket. Still the problem persists. Any suggestions?

Is it possible for the head to be cracked between oil/water galleries but not to the combustion chambers?

That would give you oil/water mixing and no detectable gas leak.

 

[astr]

Hi Dougal. I believe that the machine shop pressure tested the oil passages in the head to see if any air leaked into the coolant passages but anything is possible. The Prado is back at the shop and I will wait till they respond. I've passed on all the suggestions from this forum.

 

[astr]

Bypassing the turbo coolant lines would be my suggestion as well. You would only need to run it at idle for a few minutes to see signs of oil leaking into the cooling passages.

CT26 on the 1KZTE?

You can disconnect and block or loop the coolant lines to and from the turbo then run it for a bit to see if that makes a difference. While there is some debate as discussed in this thread, no matter which camp you're in I would think you would be fine for the amount of time you would need to see. Sounds like its pretty apparent and quickly? Just don't run run it hard and shut down right away. Do some googling and make sure you're okay with doing it.

Is your coolant level dropping at all? If so an oil sample will tell you if there is glycol and/or water in the oil, even if you can not see any.

hth's
gb

The coolant lines have been bypassed. I'm not too worried about running without coolant to the turbo as turbos ran for years without coolant. Wherever the leak is, it it very small as it took several days of driving before any oil was evident in the coolant reservoir tank. After one day with the coolant lines bypassed, no sign of oil in the reservoir tank.

UPDATE: I've been running with the turbo coolant bypassed now for a couple of days with no sign of oil in the coolant reservoir. I also don't see any oil in the turbo coolant cavity but it is difficult to examine because of the location. Next week, I'm planning on a couple of longer trips (100+ miles). If the coolant stays oil-free, I will replace the turbo.

UPDATE 2: After the longer trip (100+ miles through the mountains) only traces of oil in the coolant which could be residual oil. However, I'm losing coolant somewhere. Oil is clear and level isn't changing so coolant isn't going into the oil. I have a new turbo which will be installed when I get back to Costa Rica in a few months.

 

[astr]

At this point, the oil cooler and oil cooler cover have been replace, the head resurfaces and a new Toyota head gasket installed and the turbo coolant lines have been bypassed. Made several round trips to town (1 hour each way) and a 100 mile trip through the mountains (4 hours) with only tiny bit of oil in the coolant. This could easily be attributed to residual oil still in the system. Then we made the 100 mile return trip and the oil is back. So the leak must be in either the head or the block. The block is cast iron and the head is aluminum so I'm inclined to think it is in the head. I have acquired a new head which will be installed when I return to Costa Rica.

 

[Eurasiaoverland]

Given it's a 1KZ, I'm afraid it's very likely that the head is cracked, particularly with oil contamination combined with coolant loss. I would say it's extremely unlikely that the block is cracked.

 

[astr]

Given it's a 1KZ, I'm afraid it's very likely that the head is cracked, particularly with oil contamination combined with coolant loss. I would say it's extremely unlikely that the block is cracked.

I've checked the oil, drained and refilled, and no contamination of the oil. I am inclined to attribute the coolant loss to a poor job of bypassing the turbo as the coolant loss only began after the turbo was bypassed. Unfortunately, I'm depending on a shop to do the work because I have limited tools in Costa Rica.