Headgasket or not? - PeachParts Mercedes-Benz Forum

sknaffl · #1 02-15-2008, 07:03 PM

So...my recent purchase:

Introduction

I'm trying to rule all other possibilities out before I go replacing the headgasket. I have an overheat problem, system pressurizes quickly, no heat. HOWEVER-- I have no white smoke, and their doesn't appear to be any oil in the coolant.

So I pulled the thermostat, looks new, spring is installed towards the block, flushed the radiator, and burped the system.

While burping...heat started to work, coolant was circulating, car slowly heated up to around 80' and stabilized (vs. the usual up to max within 5 minutes)...I thought problem may be solved.

I took it out for a test drive, coolant temp stayed normal for around 15 minutes...I turned the heat fan down, and within 3 minutes, it started to overheat again quickly and the heat started blowing cold.

So...question is....on the burping procedure...what I've been able to gather from posts on here is:

1. point car uphill

2. fill upper radiator hose until overflowing then reattach.

3. start engine

4. Idle engine around 2000 RPM with expansion tank lid OFF

5. Top off expansion tank and replace lid.

6. Done

Is this correct...am I leaving something out...how long should I allow the engine to idle?

I"m thinking I'm going into vapor lock and the headgasket may not be my problem.

vstech · #2 02-15-2008, 07:46 PM

simple test for headgasket probelms.
cold engine, fill expansion tank to full line. cap tightly.
start engine, allow to build temp and see if pressure builds on upper hose. verify pressure is on upper hose, and then allow the motor to cool. if after motor is cool the pressure is still present, likely your head gasket is suspect.
another way to test is to pinch off the upper tiny hose near the expansion tank with a pinch off tool, or a pair of vice grips.
then start the car with the cap off and see if any bubbles form in the tank.
the final test is take an oil sample to blackstone labs and have it tested for glycol...
actually, your symptoms sound like a stuck closed thermostat.
have you tested the stat?
have you tested your cap?
have you pressure tested your coolant system? a leak in the heater hose could do the same thing too.

sknaffl · #3 02-15-2008, 09:31 PM

I just tested my stat...and it opened up at 200F...

I have not tested my cap, nor pressure tested.

I did just run it without a t-stat...following burping procedures...and it started to run hot..and I do have pressure on my upper hose. I clamped off the small hose running from the top of the radiator to the expansion tank, and I had overflow when I revved the engine. It hasn't cooled off enough for me to test it cold yet.

All sounds like a headgasket....it just seems weird that after I initially tried to bleed it that it temporarily ran at a normal temp,the heat blew hot, and did so for an extended period of time (15 minutes...extended by current standards)...makes me think it might possibly be something else.

disqo · #4 02-15-2008, 10:01 PM

Other members here have been fooled by a t-stat that seemed to open at the right temp in boiling water and after exhausting every other option just replace the t-stat with a new one and the problem was fixed. A new T-stat is way less expensive and time consuming that doing the head gasket.

sknaffl · #5 02-15-2008, 10:08 PM

Well...I just checked for pressure after it had cooled down a bit...and there was none.

I'll pick up a t-stat and new gasket tomorrow, re-burb, and see what happens.

You just don't know how happy I will be if I don't have to do the headgasket on this car...I had bought it with that assumption, but it sure would be nice not to have to mess with it. The previous owner had replaced the water pump once the car started to overheat...which may have been the initial problem...maybe he just didn't finish it off correctly.

sknaffl · #6 02-16-2008, 03:46 PM

Ok...so...new t-stat...re burped...ran great..drove it for about 10 miles with heat full blast...temp needle stayed between 80 and 100...UNTIL...I turned the heat off.

Almost immediately it started getting hot, heat would not blow back out hot, and pressure built up on the system and started blowing out overflow hose on the expansion tank.

I ran it at about 2500 RPM on ramps with the cap off for about 5-6 minutes...until I didn't see air bubbles anymore....do I need a steeper incline?...Or should I just let it run longer while burping.

blackestate · #7 02-16-2008, 05:41 PM

strange this ran good until you turned the heater off. IS the radiator plugged?
I would start it with the heater on and take it for a loooong drive(while staying close to home), and find some hills to work it on. May see some temp rises as it works harder, and the heater may no be enough to lower the temp unless you idle for a few minutes.
If it is controlling then I would say it is not the engine. The heater core is enough of a radiator to keep it cool. I would guess, water pump wrong (if possible) collaped radiator hose (inside) blocked radiator.

But i am new to these.

sknaffl · #8 02-16-2008, 06:39 PM

There is a cold spot on the radiator, just in front of the fan. The weird thing is that once it starts running hot, the heat won't come back on. I've been tinkering with it all day trying to get it to flow again....and no luck. I'm really convinced I have a bad case of vapor lock...mixed with a partially clogged radiator.

FYI...If anybody has one of these close by:

http://www.pullapart.com/

I strongly recommend visiting it...today I grabbed a complete center console with good wood, all new window switches, new hazard light, Tach sending unit and receiver...all for 20 bucks...

I got lucky...this one just came on the yard and I got to yank everything before anybody else got to it...but they had a bunch of dead MB's to pick from.

pberku · #9 02-16-2008, 06:48 PM

That cold spot in front of the radiator fan is normal. That's where the fan draws the outside cold air through, so its normal for that part of the radiator to be colder than the rest of the radiator.

However, the other areas of the Radiator should be warm/hot.

Hatterasguy · #10 02-16-2008, 07:21 PM

Run it without the T stat, see what that does.

It sounds like the radiator is plugged, or the water pump isn't pumping like it should. I have seen the vains on those worn down to nothing.

I'd send a sample of the oil out to the lab and see if they find coolant. If they find coolant its probably the head gasket.

blackestate · #11 02-16-2008, 07:44 PM

http://www.blackstone-labs.com/

This is a lab I have used if you are interested.

sknaffl · #12 02-16-2008, 08:01 PM

Cool..I just ordered the kit. How long did it take for you to get your results back?

Gonna pull the radiator and take it in for cleaning/repair on Monday.....hopefully that will be the problem

vstech · #13 02-17-2008, 02:29 AM

have you tested the temp of the radiator at the bottom tank? lower hose? if it's cold in center, but HOT everywhere else, the radiator is shot. odd that the radiator would be shot, but the heater core be good... since the radiator is out, can you look in the hose connections and see any corrosion or scale? it's a long shot but worth it.
if it looks clean in there, I would check the water pump.

Biodiesel300TD · #14 02-17-2008, 10:51 AM

Could your aux. water pump be bad? Those only come on when the ACC system is on. Maybe it's involved in the probem. Try giving it 12V on the black wire and make sure it comes on. Also use a volt meter to make sure it comes on when you turn on the heat.

kerry · #15 02-17-2008, 10:58 AM

Running it without the thermostat could further complicate the problem. These are bypass thermostats. When cold, the coolant circulates mainly thru the engine, when the thermostat opens, it stops the engine only circulation and forces the coolant through the radiator. So, I'm pretty sure that removing the thermostat will allow the coolant to only circulate mainly through the engine.
It does sound as if this radiator circulation is not happening either because of a plugged radiator or a problem in the thermostat system.