1996 850 Turbo Head Gasket Replacement

bugs11 · Post by **bugs11** » 07 Jul 2015, 08:39

Any tips for a newbie about to tackle replacing a head gasket on a turbo engine? If the head is serviceable, not too warped or cracked, I'll have the head planed if needed, replace the head gasket et al, put a new timing belt, water pump, serpentine belt, etc... and replace the PCV System. If the head is too messed up, I'll look into getting a used engine.

This is a car I bought 4 years ago for the kids to drive back and forth to high school. It's served that purpose admirably. The odometer was broken when we bought it, but the car had at least 150k miles at the time of purchase. So far I've replaced the front struts, rear brakes (rotors and pads), and radiator (just recently). The radiator sprung a leak and the kid drove it home, I'm sure that caused the head to warp and blew the gasket. I've got exhaust gases in the coolant and the car overheats unless I have the heater on max. The engine sounds fine and the car idles and runs like nothing is wrong, but coolant it getting blown out around the coolant reservoir cap.

The car is sitting in a friends shop. He has space and tools for me to use, which is nice. I've printed off that write up some nice fellow put together on the job, other than that it's time dig in and get greasy.

Post by **Ozark Lee** » 07 Jul 2015, 15:30

The Tracy's True Soaps writeup is pretty much the gold standard. I'm sure it, or at least a link to it, is in the repair database.

A blown head gasket is normally quite repairable following the steps that you describe. Sometimes when they eat a valve there can be other problems and if it got REALLY, REALLY, hot it can damage the cylinder walls but since it starts and runs I'm sure that you will be good to go after you get the head decked and replace the gasket. While the head is off I would have the machine shop check the valve guides and go ahead and replace the valve stem seals.

...Lee

bugs11 · Post by **bugs11** » 09 Jul 2015, 09:43

Tracy's True Soaps - that's the write-up I printed out.

Check the valve guides and replace valve stem seals, got it. Thanks.

bugs11 · Post by **bugs11** » 13 Jul 2015, 10:31

Worked on the engine an hour or so Sunday morning; took a bunch of pictures of the engine, drained coolant and oil, got it on jack stands, sprayed PB Blaster on turbo exhaust bolts, removed front passenger wheel, removed top radiator hose, coolant reservoir and thermostat - not a lot but a start. I'm taking my time and labeling everything I take off, unless it's obvious.

Question - should I get a new thermostat? The one I pulled looks fine. The thermostat gasket was hard, I know I'll need a new on of those.

Was at a get together at my brothers place in the afternoon and remembered a nephew was a former Vovlo dealer mechanic. Cornered him and picked his brain, got some good information. I described what happened, he thinks the head is ok, but definitely take it to a machine shop to get checked, including the valve guides.

Post by **Ozark Lee** » 13 Jul 2015, 20:41

Unless you really enjoy changing head gaskets it would seem that a new thermostat would be at or near the top of the list, even if it appears to be OK. It seems that leaky radiators or stuck thermostats account for about 90% of the overheating / head gasket problems that get brought up here.

In Volvo terms thermostats are dirt cheap but S.O.P. is to also change the ECT sensor at the same time and an OEM ECT sensor is not dirt cheap. If the gauge is working OK and the radiator fan is working as it should (very little) then the new ECT sensor could be postponed. Aftermarket ECT sensors are seductively inexpensive but, like most seductive things, they are a bad idea and they tend to cause more problems than they correct.

...Lee

Post by **abscate** » 14 Jul 2015, 04:29

Aftermarket ECT sensors are seductively inexpensive but, like most seductive things, they are a bad idea and they tend to cause more problems than they correct.

I'll add this to my list of seductive Swedish things to avoid.

bugs11 · Post by **bugs11** » 14 Jul 2015, 22:28

One of you guys lose a ACE CR-V 12 mm 3/8" drive 12-point socket?

I found the above wedged sideways in the driver side intake port of the number 4 cylinder when I removed the intake manifold earlier tonight. The socket looks brand new. I took some pictures, I'll try to post them if anyone is interested. All the valves looked good from shining a light in the intake ports except for the driver side number 4 valve, it had a bunch of gunk on it. Still, kind of amazing the car engine ran like a top with a socket stuck in an intake. If the socket would have rotated a 180 degrees it would have slid down and rubbed against the valve stem and bounced off the valve, imagine the ticking noise that would have made.

This tells me two things; One - somebody has had the intake manifold off before me and two, they're missing their 12 mm socket. Wonder what number 4 cylinder is going to look like when I get the head off.

Post by **abscate** » 15 Jul 2015, 05:01

If you had called Kally she would have told you where that socket was....LOL

Hmmmm...12mm for the cam cover bolts..maybe someone had the head off before you??

bugs11 · Post by **bugs11** » 15 Jul 2015, 08:59

So what's the preferred method for removing the cam cover, secure cams to the cover ala TracyTrueSoaps and remove cover and cam as one unit OR secure cams together and just remove the cover, then lift out the cams?

The latter method I found here: http://www.atthetipwebs.com/technologyi ... gasket.htm

When I talked to my nephew, the former Volvo mechanic, over the weekend he stressed the importance of lifting the cam cover off straight up, no rocking, no prying other than on the tabs.

bugs11 · Post by **bugs11** » 20 Jul 2015, 16:00

Progress report: On Saturday I removed the turbo, exhaust manifold, and got the cams lined up timing wise. I couldn't see the tiny notch in the crankshaft sprocket until I applied whiteout to the sprocket notch. After reading and watching numerous treatises/videos online regarding removing the valve cover I've decided to go with the "lock cams to the valve cover" method of valve cover removal.

Many of the vacuum lines are lined with hard plastic tubing, maybe the tubing was pliable at some time ago but now the hard plastic tubing is quite brittle and snaps easily. I also discovered that one of the vacuum lines to the turbo was not connected, the one from the intake manifold to the CBV. So now I have a very grungy turbocharger on the bench. I've been researching 850 turbochargers, anything I should look for other than shaft play in the in-out axis and excessive side to side play?