W124 603 Slight pressure in Overflow tank question

[blloyd7]

I have a 1987 W 124 300 TD
603 Engine

I have just started using the car again after maybe 4 K miles driven in the last 2 1/2 years and have noticed slight pressure buildup in the overflow tank.

I'm guessing this means that i have a head gasket going bad in some way.

Anyone know haw I can get a ball park figure to R&R the head gasket & probable do a valve job at the same time?

Any show suggestions in Northern Virginia would also be appreciated also.

Thanks for the assist.

[compress ignite]

1.What empirical method have you used to determine Unwanted/Out of Specs
Coolant Tank Pressures???
(Keeping in mind NOP [Normal Operating Pressures] are Approximately 1 Bar 14.5 PSI)
[I'd use the below HF Rad Pressure tester on the Coolant Tank(NO PUMPING)
to get an accurate reading on Cooling System pressures "At Rest" and
"Running"]
(Or any other way of introducing a Pressure Gauge into the System)

(The "Shadetree" symptom is "Hard" Radiator Hoses the Next A.M. without
engine operation.)[And you can Guess how much I'd trust THAT Idea...]

Form the Resources Tab:
http://www.peachparts.com/shopforum/forumdisplay.php?f=77

http://www.peachparts.com/shopforum/forumdisplay.php?f=51

[blloyd7]

I haven't used any method other the taking the cap off of the tank 2 hours after driving the car on a very hot day. I heard a little pressure release.

I may be misinformed but I thought that I read something on the forum several years ago that indicated that this is a symptom of impending head gasket failure.

Admittedly I know less than nothing.

Thanks for the reply.

I have had the car about 12 years.

[compress ignite]

Sustained System Pressure Retention is one of the Hall Marks of the whole
head gasket nightmare.

BUT,You may be "Looking For Trouble".
The pressures are caused by Heat,let the engine (AND System ) cool off
[Minimum 12 hours in this heat] and then squeeze the Upper Radiator hose.
'Firm to Hard hose MAY indicate the need for further SCIENTIFIC diagnosis.

[blloyd7]

Thanks very much for the reply.

I did check the upper radiator hose before I checked the overflow tank cap.
There was no pressure in the hose.

I'm looking for a good indy shop in N Virginia / close to Alexandria.
The guy who has been working on my car for the last 12 years has hired some new people and I don't like their attitude & methods.

Thanks again

[C Sean Watts]

Originally Posted by blloyd7

I'm looking for a good indy shop in N Virginia / close to Alexandria.
The guy who has been working on my car for the last 12 years has hired some new people and I don't like their attitude & methods.

The PO of my car took it to Ashgrove in Dulles for several years and the work seems to be up to snuff. A word about your coolant reservoir - you have two, one hidden the fender well is actually the overflow tank, it should never be under any pressure. The one with the 'radiator cap' on it is pressurized an equal amount whenever the cooling system in pressurized.


Do you see any oil in the coolant or any signs of coolant in the oil? ('milk chocolate' on the dip stick or oil cap)

[jt20]

remove the cap after a complete cool down.


this usually means overnight, at least.

[jonbobshinigin]

Couple things:

What number is the head? #14 is stock and the most prone to failure. Mine is original #14 at 185k and it is fine. I have seen several of these cars with 300k+ miles and they are fine.

How many miles are on the vehicle?

[blloyd7]

Haven't bothered to look at the head #.

I have receipts going back to the original owner & the second owner (wife's family) and I'm the third owner, having owned the car 11 years.

The receipts total over 39,000.00 dollars including 20K that I have spent.
3,200 spent this year.
With the 54,000 original sale price the car is close to a 100 thousand dollar car.

None of the receipts indicate any previous issue with overheating.


Car has 245,000 miles. Runs sweet.

[jonbobshinigin]

What I heard is to check the top radiator hose for pressure while vehicle is cool and off. Make sure it is soft. Leave hood open and crank car up and see how longs it takes for the hose to pressurize. Apparently if it pressurizes in under 2 minutes, you have problems.