Blown head gasket, thermostat

What are the symptoms of a blown head gasket? With a blown head
gasket: Is the car supposed to overheat while running or when it’s
idle? If the coolant reservoir is bubbling and hissing could it be
this? Can a new thermostat be faulty? Could it cause the coolant
reservoir to be hissing and bubbling? I have a 2001 Chrysler 300m.

 

Here are the potential types of failure and their associated symptoms, not
all symptoms
may be present:

1) Cylinder sealing ring failure

a) power loss
b) Failure of compression test
c) failure of cylinder leakdown test
d) engine miss
e) coolant dripping/steaming out of tailpipe
f) coolant loss
g) hard starting
h) loud noise in engine compartment
i) exhaust gases in coolant
j) runs rough after initial starting

2) coolant passage to oil passage failure

a) water in oil (pull oil plug and if brown froth comes out water is in
there)
b) coolant loss

3) coolant passage to outside failure

a) coolant loss
b) coolant leaking from gasket line

4) Coolant to intake manifold failure

a) check engine light for lean running on

Here are the common ways to test for a blown head gasket other than symptom
observation:

1) Take sample of coolant to radiator shop and have them test it for
hydrocarbons
2) Let engine sit overnight and in morning when it's cold, disconnect
ignition and crank it over,
then pull plugs (real fast) and check for coolant on the plug end. Or crank
it over when
the plug on suspect cylinder is out and see if it blows coolant.
3) Purchase chemical type block tester at a place like NAPA and use as
directed
4) Using compressed shop air pressurize each cylinder one at a time and
see if coolant level at rad cap rises (cold engine)
5) Run engine till hot then do compression test on each cylinder
6) Go to a shop with an exhaust gas tester (tailpipe sniffer) and when
engine running
have them stick the sniffer in the overflow bottle and see if it's exhaust
gas present.


Good luck with it and remember if coolant has been present in the oil for
any length of
time (like more than a few weeks) your rod bearings are probably heading
south and
even if you fix the head gasket the engine may start knocking shortly
afterwards.

Ted

 

Head gaskets can fail in numerous ways. One of the most common ways, in
recent-model cars, is for combustion gas under pressure to leak into the
cooling system. This causes consistent overheating, bubbling/boiling of
the radiator and overflow tank, and an exhaust smell detectible when
sniffing the bubbling overflow tank (in fact, one diagnostic test for a
blown headgasket is to place an exhaust emission test probe above the
fluid level in just such a bubbling tank.)

The car is never *supposed* to overheat. With a blown head gasket, it may
exhibit overheating behaviour when idling or under load.

Certainly could.

Certainly can.

Yes.

When you changed the thermostat, did you bleed the air out of the cooling
system? This is a necessary step.

 

Good point, Daniel.

To the OP: That engine has a bleeder valve on top front of the engine.
Looks just like a brake bleeder. Lean over the front bumper and look
straight down on top front of the engine. It is recessed a little bit.

The pressure bottle steals some coolant circulation and helps remove
trapped air, but the bleeder valve needs to be used initially for any
large pockets. Open the bleeder valve with the engine warmed up (system
pressurized). Close it when water starts coming out. Top the pressure
bottle off to the full line (don't open the cap until it's cooled down
again). After at least an hour of driving (not just idling), check the
bleeder again, check bottle level, and top off the bottle again.

Also, when closing the bleeder, use only light torque to snug it - it
doesn't get torqued hard like a bolt.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

In addition to what the others wrote, check your oil to see what it
looks like. If it looks more like chocolate milk rather than regular
dark brown motor oil, then you have coolant leaking into it. If this is
happening, fix it NOW! Coolant in the oil will take out the bearings.

 

When you do this it is a USEFUL modification to the thermostat to drill a
small hole in the thermostat housing. This allows "air" to bleed out of the
system. Dan suggests the same as Chrysler Co (and others) - to bleed the air
out of the cooling system after doing several types of cooling system
service. The hole-in-the-thermostat body is a "fix" that few mention, BUT it
works! Period. The air bubbles simply have a way to get out of the engine
block and into the rad/expansion tank part of the system and "vent" out into
the atmosphere.....

Ken
Winnipeg
Canada

 

(1) I believe the hole is in the OEM thermostats.
(2) Based on some discussions on the 300M Club forums, the hole also
serves a second purpose for racing when cylinder and head temps can rise
extremely fast - the hole helps keep the temperatures from spiking,
which also prevents excessive knock retard from reducing performance.
Not important for street use, but FYI.

I'm getting OT relative to the OP, but trapped air aside, I believe this
hole also helps with the thermostat opening a little quicker at initial
warmup by letting a little water flow and communicating the cylinder &
head temperatures a little quicker (might be done for emissions purposes).

For trapped air, I would think that, even in the absence of the hole,
once the thermostat opened, the air would no longer be trapped. That is
particularly true on the LH cars, since the thermostat is way down low
on the side of the engine.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

It's also an *unnecessary* modification, because the thermostat already
has such an air bleed hole. Sometimes it's on the T-stat flange, with or
without a jiggle pin installed. Sometimes it's a small notch in the
thermostat valve plate, which you wouldn't see if you were seizing the
thermostat with one hand and going trigger-happy on an electric drill with
the other.

 

Yes, I suppose there are those "trigger-happy" individuals who would do
exactly as you say - but probably only once ;-)

Am I right in assuming that EVERY manufacturer of thermostats makes them with
bleed holes? If so, then I have had an epiphany. Thanks for that.