Please help me diagnose head job vs. intake job

[Frankhagen]

2004 Buick LeSabre Custom 3.4 L 3800 - 110K miles

I started noticing some rough idling after seeing my check engine light come on. I ran the code and cyl 3 misfire showed. I changed wires and plugs and then got the same code again. I swapped coil pack 2-3 with 3-6 and same cyl 3 was misfiring after. Meanwhile I noticed my coolant reservoir was milky and I also noticed some "water oil" in between the area of the front head and the intake (near fuel injector 3 and 6). My upper and lower radiator hoses were collapsed until I opened up the radiator cap. At this time the oil looked totally normal. A bit low actually, so I added. I drove it around and the code came right back up showing cyl 3 misfire.. but I had the coil packs swapped so I was thinking it was the ignition control module... I switched the coil packs back and was going to bank on just buying a new ICM. I decided to clean up the ICM with contact cleaner and reinstall it with the coil packs and then I started it up and white smoke just came puffing out of the exhaust. I ran it down the street and got it back without any overheating and decided to check the oil and all of a sudden the oil was almost all the way up the dip stick and pure chocolate milk.

My question is from your experience.. should I do an INTAKE job or a HEAD job? I heard that the 3800 engines are commonly misdiagnosed and the customer gets a head job when an intake job could have fixed the problem. Any advice would be greatly appreciated. 🙂 I want to dig into this baby but I have never done a 3800 before so any help would be amazing!!!!!

THANK YOU SO MUCH!!!

 

[Lubener]

The intakes have to come off anyway. I don't know if you ever overheated? I would pull the upper and lower intakes and look for an obvious failure before considering head gaskets and from what I have read isn't near as common of a failure on the 3800. If coolant is getting in the oil, failure of the lower manifold gasket would provide an easier path into the crankcase.

 

[Frankhagen]

Thanks for the reply!

It never overheated. Once the problem started I parked it. I have another car thankfully haha.

But I did have starting issues after swapping the coils back but all I did was clean things up. YES I put the wires back correctly.

It just sits in the rain right now.. what should I buy next? A complete head gasket kit and just start with the intake? OR buy only intake gasket set?

 

[Lubener]

Myself, I would get an ATP upper manifold/kit, metal coolant elbows and a metal backed lower intake gasket such as Felpro's and not headgaskets (hopefully) at this time. I would want to see what things look like once you get the manifolds off. If there is an obvious failure seen, I might stop there as far as head gasket time goes because that likely was the issue but to fill the crankcase like that, something failed in a miserable way. Cylinder/ leakdown tests while the manifolds are off tell how the H.G./valves are. I had a Mercury 3.8 which began as a brief cold start misfire, the head gasket then failed in a big way, filling the crankcase with coolant and sending so much pressure causing the coolant bottle to overflow.

 

[Frankhagen]

So a failure somewhere in the intake could cause the coolant to be in the oil? Does coolant run through the intake area? I'm worried about ripping off the top end and not seeing any obvious damage and then put it back together and the problem comes back. I dunno I guess I'm overthinking this haha I just want to do it the cheapest

 

[GliderRides]

A compression test would show if the head gasket is leaking. If it's just the intake manifold, the 'wet' cylinder will still make decent compression. If #3 spark plug is washed clean, that's the cylinder to check compression on. If the head gasket is ok, compression reading may be a bit high, due to the coolant in the cylinder. If the head gasket is blown, there can still be some pressure, but a lot lower than other cyls., or even zero.

Yes, failed intake/intake gasket can dump coolant into the crankcase.