Hey guys, my 2006 Dodge Caravan recently overheated and we’re trying to get a clear idea on what could be going on before we completely break this thing down. To begin most of the cooling system failed at once. I had to replace the radiator, cooling fans, thermostat, and it seems like the water pump may have issues as well but we’re trying to figure out our engine troubles before we spend more on the cooling system. The vehicle ran fine for my 20-minute commute at 70 mph on toll roads. As soon as I got on the service road the temperature started rising, and as I was trying to pull off the service road to cut the car off the engine misfired and shut off. The van starts, is hesitant at first sometimes, and is rough at idle and especially in reverse while backing out of a parking spot or something slow. The van FEELS to run fine at higher speeds and takes the normal amount of time to get to temperature, but as soon as it gets to the normal operating temperature it starts to rise significantly and tries to overheat.
Now we initially thought it could possibly have a blown head gasket. But, there are no signs of a blown head gasket other than the rough idling. There is no coolant in the oil, initially there was no white smoke from the exhaust pipe, and no leaking coolant from behind the exhaust manifold. Our second thought is a burned exhaust valve. This seems to match up pretty perfectly with the symptoms: Rough at idle, loss of power(car battery died gradually while trying to take it around the alley today to the back of the house), tail pipe sucks in on the dollar bill test, stalling/hesitating to start, and of course the misfire as the engine code readout pointed to. We did a compression test this evening and here were the results:
What’s interesting here is that the misfire was on 2 but the compression test would point to 4 having the problem instead from what I’m understanding.
We’re just looking for any thoughts any of you guys have before we get everything taken the rest of the way apart so we can have as much of a heads up as possible with what we may be dealing with.
I’d make sure the fans are running when needed. Sitting still at a light with no fans running is path to overheating.
Burned valves or blown head gasket both mean the heads must come off, as you know. Would be nice to know the wet compression on #2, too. I’d pay more attention to the mechanical testing rather than to figure out why more misfire codes are not set. Seems like the valves or the gaskets are leaking in 3 and 4.
So rather than guess pull the heads and look. Squirt brake-kleen into the ports to see if it leaks past the valves.
Alright, so we replaced the spark plugs yesterday just to rule that out as one or two NEEDED to be replaced anyways. Engine still ran rough at idle and low speeds. So we drove right in and took the front head off and we were expecting to see and obvious burnt valve. Nope, nothing extremely noticeable. We’re tackling the back one this evening and going to see what’s going on there. As far as the front there is something causing the compression issue on #4. Anybody have any thoughts of what could cause that if not a blown head gasket or burnt valve? Any tests we should be doing to narrow anything down or rule anything else out? Any ideas welcome. I’ll clarify that the head gasket had no signs of damage as well. Here’s a pic of the head:
With the clean chamber for cylinder # 4 it appears that the head gasket was leaking. MLS head gaskets don’t “blow” like the head gaskets 30 years ago, they leak after overheating because the cylinder head is warped. Check the cylinder head with a straight edge to see if it is warped.
Squirt some brake-kleen into each exhaust and intake port one at a time with the head mating surface down. After a couple of seconds, check to see if the solvent has leaked out of the valve. That is how you check for bad valve seal.
Agree with @Nevada_545, tho, notice the head sealing surface next to that far left exhaust valve. Looks like the water passage breached into the cylinder.
The center cylinder looks awfully clean in the quench area, too.
Which cylinders are you showing in your photo OP? ID them from left to right. The clean exhaust valve on the left most cylinder stands out the most to me, but the middle cylinder looks like it has been washed with soap and a scrub brush.
One thing about these heads is that they have very large water jackets compared to other cylinder heads. That is probably because they were designed by Volvo Engineering.
It looks to me like the exhaust valve on #2 is burned so I would not be surprised if it fails your brake clean test. If it does pass the test, I think it is still on its last legs and should be replaced. Personally at this point, I’d replace all the valves, especially the exhaust. I never had any luck grinding exhaust valves. Intake valves are OK to grind but sometimes it is just cheaper to replace them. If they are in really good shape, just clean them and re-lap them in place, I’ve had good luck doing this too.
You did have a blown head gasket BTW. It could have blown due to overheating and you may still have a problem that needs to be solved before you blow the new head gaskets. If you have torque to yield, be sure to replace them, they are not reuseable. Be sure to check the head mating surface with a good straight edge to make sure it isn’t warped. If you have an aluminum block, check that surface as well and if both are warped, then check to see if the warps match.
Put a measured thickness between the head and block at three locations with plasti-gauge in several locations to determine the match. I would not machine anything if the plasti-gauge is all the same width.
