2004 S80 T6 Strange Overheating Issue

SaulGoodman · Post by **SaulGoodman** » 14 Sep 2018, 21:03

Hello everyone,

I am hopeful someone will be able to help me out. I am stumped.

I have a 2004 S80 T6 with 134K miles and an overheating issue. There is no loss of power, engine runs great, no misfire, no oil in the water, no water in the oil. I have removed both upper and lower hose and ran water through the system. I have bled it a few times through the reservoir. It heats up normally, then will start to climb after about a mile after it is warmed up. The fans kick in, and you can hear a crackling sound from the reservoir, but it is not leaking or overflowing, but is boiling.

Any ideas what this could be? It will run forever and not overheat with the reservoir cap off, so I think the thermostat and water pump are working correctly. Could it be a head gasket or cracked block even though it is exhibiting no symptoms at all?

Please help!!

Post by **RickHaleParker** » 14 Sep 2018, 22:02

Do a chemical block test at the reservoir to determine if the gas is water vapor from boiling or exhaust gases.

[youtube][/youtube]

Post by **SuperHerman** » 15 Sep 2018, 08:31

The block exhaust test suggestion is solid. I had a 2004 2.9 na which had a bad head gasket from about 30k on based on the service history. Was in and out of the dealer and all sorts of parts were changed. Then once out of warranty the records showed more of the same at private shops under new owners. I bought it w 80k or so and a full blown oil/coolant stew. I pulled the head and found a bad head gasket. Machine shop checked the head, I measured and examined block and all checked out. So my guess is it had a faulty head gasket from the start. Very rare.

You can pull the spark plugs and look at them and the piston tops to look for coolant cleaning signs. Meaning the coolant is steam cleaning the pistons where the leak is. They should all look like an engine w 135k on them - consistent and slightly carboned/oily. If one or two are clean that points to a head gasket (most likely) but you also may have a cracked head or other issue. By 2004 the 2.9 was pretty much bug free.

The exhaust block gas test is the easiest way to see if that is your issue.

Curious how long you have had the car and when the issue manifested? Also the coolant cap may be bad or water pump or thermostat. Start w eliminating the head gasket and then move to the other items.

I have the block tester so I would start there (rentable from Autozone but you have to buy the fluid). If I didn’t have the tester I would start w pulling the spark plugs after looking at oil and coolant for cross contamination. Then I would look at water pump and thermostat.