Pressure on the coolant system..... - Page 2 - PeachParts Mercedes-Benz Forum

mplafleur · #16 07-15-2010, 12:06 PM

What you describe is normal IMHO. No need for a head gasket change.

Your coolant may be a little low or your sensor a bit flaky.

Just read the last note. There may be a small leak. Is there oil in the coolant, or bubbles? If not, still no reason to change the head gasket.

Fulcrum525 · #17 07-15-2010, 02:24 PM

Quote:

Originally Posted by mplafleur

What you describe is normal IMHO. No need for a head gasket change.

Your coolant may be a little low or your sensor a bit flaky.

Just read the last note. There may be a small leak. Is there oil in the coolant, or bubbles? If not, still no reason to change the head gasket.

Yeah i'm changing my mind again and thinking that i'm just overacting about the pressure on the line. A co-worker of mine just bought an 87 300D and he gets the same amount of pressure on his. Also i've just been reading through this thread

have overheating issues?? Testing info

I forgot to mention that one my electric fans isn't operating and the other one tends to only want to come on when the AC is engaged (Bad temperature sensor perhaps?) My engine stays at normal operating temperatures unless its VERY hot out or i'm in stop and go traffic. Also it never overheats but just gets hotter then normal (Halfway between normal and overheating) I'm using the clear MB coolant.

I'm now thinking that my NEW radiator is indeed leaking which is why i'm loosing coolant slowly over a period of weeks, Since a picture is worth a thousand words here are a few shots of the new radiator that I put in and the odd yellowish residue on the top of it. I'm also thinking about replacing my thermostat to be safe (I'd rather all that then have to go through a head gasket job)

tbomachines · #18 07-15-2010, 02:30 PM

Your leak is at the upper hose in the first picture. In all of my wonderful cooling system experiences, the MB coolant turns white and powdery when dryed and heated. Unless that is indeed all over the rim of your radiator (hard to tell since it isnt focused)

Fulcrum525 · #19 07-15-2010, 02:41 PM

Quote:

Originally Posted by tbomachines

Your leak is at the upper hose in the first picture. In all of my wonderful cooling system experiences, the MB coolant turns white and powdery when dryed and heated. Unless that is indeed all over the rim of your radiator (hard to tell since it isnt focused)

Yeah i'm finding it difficult to get clear photos but it's along the rim on both sides of the radiator. Also car is sitting now....i'm going to check it from time to time over the next few hours to ensure that the pressure goes down.

Fulcrum525 · #20 07-15-2010, 07:52 PM

Alright it's been 6 hours since I last checked and the good news is that my hose is nice and soft as it should be

Fulcrum525 · #21 08-24-2010, 04:50 PM

Quote:

Originally Posted by Fulcrum525

Alright it's been 6 hours since I last checked and the good news is that my hose is nice and soft as it should be

And back to square one again. Put ANOTHER new radiator in yesterday and so far it hasn't leaked a bit (Good news cause the last one definitely leaked around the top edge) Bad news, still a heck of a lot of pressure on the system and it looks like the coolant deciding to come out of the expansion tank somehow this time. I'm going to give the upper hose a squeeze in the morning and if it's hard i'm biting the bullet and taking it to my indy to install a new head gasket.

It's not cheap but it's a heck of a lot cheaper then a new head....

Brian Carlton · #22 08-24-2010, 05:36 PM

Quote:

Originally Posted by Fulcrum525

I'm going to give the upper hose a squeeze in the morning and if it's hard i'm biting the bullet and taking it to my indy to install a new head gasket.

It's not cheap but it's a heck of a lot cheaper then a new head....

This is just plain foolish.

To pull the head off a properly running engine without some data that supports the claim of a bad head gasket makes no sense.

There is no urgency to accomplish this task and some tests should be accomplished to confirm or deny it. Testing includes an oil analysis for potential glycol in the oil and also includes a test for combustion by-products in the coolant.

If either of these tests are positive, you then have a basis for pulling the head.

However, be prepared for the worst if you do pull the head. Many times the culprit is a cracked head and not a simple head gasket.

Fulcrum525 · #23 08-24-2010, 09:25 PM

Quote:

Originally Posted by Brian Carlton

This is just plain foolish.

To pull the head off a properly running engine without some data that supports the claim of a bad head gasket makes no sense.

There is no urgency to accomplish this task and some tests should be accomplished to confirm or deny it. Testing includes an oil analysis for potential glycol in the oil and also includes a test for combustion by-products in the coolant.

If either of these tests are positive, you then have a basis for pulling the head.

However, be prepared for the worst if you do pull the head. Many times the culprit is a cracked head and not a simple head gasket.

I know, i'm quite paranoid at the moment though. There is obviously way too much pressure on the system and the engine does have a new head on it. The head will be inspected if we do the gasket or course to confirm that it isn't cracked. Again the engine got quite hot the day the radiator went but it NEVER went above the white line so i'm hoping that my new head managed to withstand the high (but not redline) tempurature without cracking.

Also the idea to do a chemical test on the coolant didn't pass me by and I bottled some of my coolant yesterday when I replaced the radiator. The question though is where would I bring it for testing?

That last statement is completely disheartening. I'm going to sleep now...

4x4_Welder · #24 08-24-2010, 10:08 PM

As any medium is heated, it expands. In a confined space, that expansion turns into pressure. I would check the pressure cap and see what it relieves at, if it's within specs then it's all as it should be. If it is out of spec, then replace the cap and see if you have any other issues. If it does not use a pressure relief cap, then be sure to only fill it to the "full cold" mark when cold, otherwise the air left in the system will not compress enough and the system will be overpressurized.

dagObx · #25 08-24-2010, 10:30 PM

Quote:

Originally Posted by Brian Carlton

This is just plain foolish.

To pull the head off a properly running engine without some data that supports the claim of a bad head gasket makes no sense.

I'll have to chime in with Brian on this one. I really think you are overreacting. I have a '87 300D with the #14 head. I watch the engine temp like a hawk & even have some residue on my radiator. The hoses get hard when the engine is pumping out heat (as is should) & then get softer as it cools. This is as it should be, no cause for alarm.

Others have suggested diagnostic courses of action that should be tried before pulling the head. You said it had a new head on it, what number is it? If it is not a #14 head, I certainly would not be too worried about it. Later head castings (higher numbers) were no where as suseptible to cracking.

Lots of folks on this forum have a LOT of experience with these MB cars. I would try the other diagnosis items LONG before I would worry about pulling the head...IMHO

tbomachines · #26 08-24-2010, 11:04 PM

My persistent question is this: Why on earth is the expansion tank cap not venting? It is designed to alleviate that very problem of having too much pressure.

vstech · #27 08-24-2010, 11:14 PM

first thing in morning open hood. squeeze the upper hose, is it hard? if not, does fluid flow into the expansion tank? yes, good, no? air/not filled hose.
next.
start the car. let it idle for 1 minute. check the hose. is it HOT? is it Hard? no? good. shut down the car. pull the tank cap, look it over VERY WELL. how old is it? are there any cracks in the seal or the seat/spring pocket?
what pressure is the cap? yours should be a 140KPA I think... (about 22psi) perhaps you could drop it to a 120 or a 100, and see if it vents pressure better.
take your car to a radiator shop and have the cap TESTED, and the cooling system pressure tested for leaks. sitting for 10 minutes at 15 psi should be a solid report of a tight system.

dieseldan44 · #28 08-24-2010, 11:49 PM

I have a similar problem with my 85.

I bought this tester and the tests came back totally negative.
http://www.amazon.com/UVIEW-560000-Combustion-Leak-Tester/dp/B000NPDL76/ref=sr_1_fkmr1_2?ie=UTF8&qid=1282707791&sr=8-2-fkmr1

This tests for combustion gas in your coolant. If the coolant is being pressurized by exhaust, this detects even the most trace amount.

If this test comes back negative, relax and look elsewhere. I haven't solved my issue, but I have stopped worrying about it. I think the extra plumbing of my wvo system may have something to do with it, I don't know. I tried a new pressure cap too, but enough about me.

Don't drop $1000 on a head gasket!!!!

Where in ct are you? I'm going to New Haven Friday from Boston and would gladly stop by with my tester. If not then I'll be traveling the length of 84 week after labor day.

tbomachines · #29 08-25-2010, 01:33 AM

Hey fulcrum, I'm coming up to CT in about a week to finish up my swap. If you don't want to blindly gamble and spend the money for a tank cap you can swap mine out for a bit and see if it builds the same pressure. I also have a spare from the donor car but not sure of its condition.

Edit: haven't checked but this is assuming that the caps are the same from the 617 to 603

hey_allen · #30 08-25-2010, 02:40 AM

Like DieselDan linked to, the tool to test for combustion gas presence in the cooling system is used on the car, not on a coolant sample.

It works by replacing the cap with the tapered rubber stopper from the tool, and then using the squeeze bulb to draw whatever air/exhaust mix is inside the cooling system through a test liquid.
If your cooling system has any combustion gasses in it (be it due to head gasket, cracked head/cylinder, whatever..) the test fluid changes colors.

In the last time I used one of these, on a gas engine, I also found out that it can give you a rough gauge of just how bad the leak is, based on the speed of the color change.
In that engine's case, it was VERY bad, as the mechanic who loaned me the gauge had never seen the fluid change so quickly.

On a related note, there may be two fluids, one for gas engines, and one for diesel engines. At least one vendor seems to have gone to a single fluid though.

http://www.napaonline.com/Search/Detail.aspx?R=BK_7001006_0282440235
http://blockchek.com/instructions.htm

PS: The tool should go for $40-60 from what I'm seeing. The NAPA website doesn't seem to specify weather it works with diesel, but it goes for $45.

Oops, I forgot one other option, and stumbled across it again.
If you have any emissions testing shops that do work beyond just testing for certification, they might be willing to use their exhaust probe to sniff your cooling system for HC (hydrocarbons). Just make sure that the probe doesn't actually make contact with the coolant, as it apparently ruins the probe if it does.
From one website's account, this test is one of the most sensitive to the exhaust gasses in the cooling system, and for the cost of the machine, I can see why it would be.