2007 Suzuki Forenza 2.0, Rough Running Engine and Overheating Issues

This 2007 Suzuki Forenza with a 2.0 came into the shop a couple of months ago with a customer concern of a rough running engine and an overheating issue. We felt pretty confident we were looking at a blown cylinder head gasket at this point; but, we wanted to "test and not guess".

There are a couple of ways to check for a blown cylinder head gasket. One way is to pressurize the coolant system and, with the spark plug out of the missing cylinder (or all plugs removed), using a bore scope in the cylinders to check for seeping coolant. Another way is to use a 5-Gas Analyzer to check for combustion gases in the coolant system. The third option, similar to the second, is to do what is called a block test.

We opted for the third option. It is a method we have used often with great success.

Before this, however, we wanted to perform a visual inspection.

When the customer drove the vehicle up to the shop, we noticed the tell-tale white smoke out the tail pipe. It was quite pronounced and the smell of coolant in the exhaust was noticeable.

The next visual inspection was of the oil. As you can see in the pictures below, the milky look to the oil is a sure sign that coolant has entered the crankcase.

We let the vehicle sit and then took the cap off the coolant tank. We noticed when we started it, fumes coming out of the tank.

Per the instructions with the block test kit, we let the vehicle run for about ten minutes and then performed the test. The kit comes with a clear tube and a fluid. The fluid is added to the tube, then you place the tube over the coolant tank opening. You apply vacuum to the top of the tube, in this case we used a hand-held vacuum pump, and apply vacuum for a minute or two. If combustion gases are present in the coolant, which they should not be, then it confirms a problem. (If there is a problem, the fluid, which is blue out of the bottle, will turn green.) Of course, it could be a blown head gasket, a cracked head . . . etc., but you confirm there is a problem that calls for a top-end engine tear down.

In the picture below, you see the fluid just added to the tube. You can see it is a light blue color out of the bottle. If the test passes (meaning no combustion gases are detected in the coolant system; hence, no blown head gasket) the fluid will remain blue. However, if the test fails, (combustion gases detected) then it will turn green within a minute or two.

Here I am showing (minus the fluid) how the tube fits on the coolant tank. (It is minus fluid because I just took the picture to demonstrate how to do it.)

As I applied vacuum (via the vacuum pump) to the top of the tube, within seconds, the blue fluid changed to green. This confirmed a failure at the mating of the head and block. Now, it was time to remove the head, send it to the machine shop and replace the head gasket.

We replaced the head gasket, timing belt and water pump and other odds and ends. Put it all back together and the vehicle ran nice and smooth. We test drove it a few miles and shipped it to the customer.

2007 Chevrolet Colorado LT 3.7 2WD, P0128 Code

Just FYI, the Colorado pictured above is not the one this issue occured.  I did not take a picture of it, but I thought this one (another customer's) would do.

This vehicle came in with a customer complaint of the CEL being illuminated.  I ran the codes and discovered it had a P0128 DTC.  P0128 is a Coolant Thermostat code.  However, some tests need to be performed before relacing a thermostat.

I first performed tests on ECT and its wiring.  Everything checked out okay.

I then started the vehicle and let it idle for several minutes, long enough to reach normal operating temperature.  Below you will notice the temp hand has hardly moved even though the truck had been idling for several minutes.

I then connected my diagnostic tool to see what temp the sensor was showing.  Again, as with the temp hand, it was woefully low.  Sorry for the glare, but the temp is reading only 140 degrees. 

After taking it for a short drive, the temp remained very low.  It only got as high as 150 degrees.  Obviously, there is a problem in the coolant system not allowing the vehicle to reach normal operating temperature.

After gathering the evidence, I decided it was time to take a look at the thermostat.  To easily reach the thermostat on these vehicles, raise the vehicle and go through the driver's side wheel well.

After removing the left tire, the inner fender trim has to be removed. 

Here it is on the floor.  It has six retainers holding it on.

Now, the thermostat housing can be observed.

In order to drain the coolant on this vehicle, the lower radiator hose must be removed from the radiator.  There is no drain plug on these models.  It can be a bit messy, but not too difficult.  In the picture above, you can see the lower hose connected to the thermostat housing.

There are two 10 mm. bolts holding the housing on.  Below is the entire assembly (lower hose still attached).  On these models the thermostat, housing, and gaskets come as one assembly.

Upon inspecting the thermostat it was obvious what the problem was.  Notice below (I'm pointing to it) that the gasket has come out of place.

This was allowing coolant to bypass through the opening.  As a result, the thermostat was partially open and not allowing pressure to build in the system or allow the coolant to reach normal operating temp.

Once the new one was installed and the coolant was at full, the temp hand at idle came up as it is suppose to do.  The difference in temp can be seen below on the scan data.

Now the temp is reading around 200 degrees.  This is where it should be based on the amount of time it was idling. 

A quick test drive and check for leaks and a recheck of coolant level (after the vehicle had cooled) and the repair was verified.