Diagnosing 9-5 V6 Coolant loss [Archive] - SaabCentral Forums

: Diagnosing 9-5 V6 Coolant loss

31st March 2011, 07:03 PM
I have a 1999 9-5 V6 with 141,000 miles on it. Engine is all original. Radiator was replace 4000 miles ago. I'm loosing a little bit of coolant and the problem is intermittent. There is no coolant in the oil and I don't see any oil in the coolant. I took it in to the shop and they could not find anything wrong. They had it on a pressure test for 45 minutes with no pressure loss. A mechanic friend told me it sounded like a head gasket was starting to go. I read on this site that head gaskets are usually not a problem and that perhaps it is a bad oil cooler.

How do I diagnose this problem? Does anyone have any experience with this?

PS: I want to keep this car until at least 200,000 miles - it is still beautiful!

31st March 2011, 09:42 PM
Did the coolant loss start before or after replacing the radiator?
Diagnosing coolant loss is easier said than done sometimes. There are a few tests you can have done to find coolant though. An oil analysis test will tell you if there is coolant getting into the oil, especially if the amount is so small that you can't detect it visually. Generally you will have some clues if there is coolant in the oil. You'll get kind of mustard/slime looking droplets on the dipstick and on the bottom of the oil fill cap.

A bad head gasket can leak to either the oil passages or to the combustion chamber. If it leaks to the crankcase, you will likely not have oil in the coolant. If it leaks into one of the oil pressure passages there may be oil in the radiator or reservoir.
It is not possible to tell if the oil cooler or a head gasket is at fault if coolant is getting into the oil, or vice versa, without replacing parts. However, if you do a block test and find exhaust gases in the coolant, a head gasket is probably also at fault for the cross contamination of fluids. You replaced the radiator so coolant loss to the transmission fluid can be ruled out. In my experience there is generally a lot of transmission fluid in the coolant if the trans heat exchanger leaks, and the trans will stop working correctly, often stop working altogether.

Since you currently have no fluid contamination, keep an eye and a nose out for leaks, and the smell of coolant. You can add UV dye to the coolant to help find leaks. Keep a close eye on engine temperature while driving. If you find no visual evidence of a leak, do a block test to see if exhaust gases are present in the coolant.

1st April 2011, 05:04 AM
Leak occurred after radiator was replaced. But the cooling system passed a 45 minute pressure test ok.

Occasionally I find coolant on the garage floor. But only coin size puddles. Also on the road while I am driving, I have had the "add coolant" message come up on the computer, so it is loosing coolant while running. It only happens when the engine is at normal operating condition. I'm going to try to see if I can see coolant leaking at the heads.

1st April 2011, 06:34 AM
While the head gaskets on the v6's generaly don't go, it's not unheard of for an early v6 gasket to go. I think they were either a slightly different design or a different material. I wouldn't rule out the HG entirely since it is a '99

1st April 2011, 08:38 AM
I'm planning to tackle a 99' V6 "likely" oil cooler replacement. The fluid on mine comes from the rear of the engine between the heads, that is the right side when facing the vehicle. The oil cooler is between the heads in the V of the engine, a surprise locations for me. Your leak is certainly hard to see without removing hoses and components. Pay particular attention to where the drop is showing up. Coolang bypass hose is another possibility. Check out: http://www.fixmysaab.com/9-5_repair/cbv/step1.asp?nsteps=2&nointro=1 My research shows the 99 V6 oil coolers were prone to corrosion. thesaabsite.com has an oil cooler kit for $260 - replacement cooler and gaskets.

1st April 2011, 02:15 PM
I found this helpful diagram of the cooling circuit:

I'm not sure that that is the same for the V6, but the Heater Bypass Valve (Item #46) is known to fail and leak coolant. There is a replacement guide in the FAQ section. As for passing the pressure testing, is it possible that this section of the circuit wouldn't be tested if the AC/Heat was off??? Just a guess here...

1st April 2011, 05:15 PM
Or could be like in my car. 2003 V6. The oil cooler cover is leaking