Pressurized radiator on cold engine

ron234

New member
I've spent some time searching the forum for more information on this... but... my symptoms aren't quite the same as other things I'm reading.

Here goes:

Your basic 2006, 2500... higher top converted cargo-camper van.

1) In the morning after Sprinter has cooled down, if I check the coolant, the top BLOWS off with a lot of pressure (I use a towel so it doesn't bop me in the face).

2) There is NO OIL in the radiator fluid.

3) There is no water/white stuff/emulsion in the oil (I change it myself... 3 x's now...nothing, ever)

4) No white smoke out the exhaust.

5) I have been losing coolant... depends on heat and how much I drive. it's not a Ton... maybe 2 cups every 1200-1500 miles?

6) I had the radiator pressure tested... no leaks.... but there was a small tear in the cap, so we replaced that... it's been a few months... no change in anything.... still pressure blows on even a cool engine EVERY TIME I check (First I thought it was because I was going up and down in elevation!)

Also, I still have a consistent amount of coolant loss.
The coolant light is usually on (even within 15 minutes of driving after I've topped up. I will check it the next morning and there is no noticeable loss of coolant by then, but the light is still on MOST of the time... so... I think the light must be dead most of the time)

7) No leaks on the ground under the van

8) I looked for white residue indicitive of a leak on the engine somewhere... nothing I can see... [I'm not sure where the water pump is though. I tried looking everywhere, though]

9) Maybe I'm running a bit hotter than most people on this forum. The van temp gauge runs just under 215F when I'm going up and down hills in Colorado. Sometimes it might creep over that, but then the fan kicks on and it stays steady, even across the desert. Never overheats into the red. (We don't tow anything or have a lot of weight in the van because we are both very small people with small clothing.)

Is this something I can just ignore? It's not causing problems now, I guess, but... is it going to cause problems later?

I still get 26 mpg so long as I don't drive 80.... I have plenty of power... Most driving is highway miles. But we live in the van now, so... I'd like to solve it now if it's going to cause more problems later.

THANK YOU!
 

220629

Well-known member
Sounds like you've done your homework.

Number of miles? If high (maybe even if not??), it could be your water pump seal. The water pump is the shaft which the large cooling fan is mounted on. Mine leaked enough to need top off for quite some time before drips showed when mine went bad, but that doesn't mean yours is bad. Just worth checking closely.

Pressure when cold....
Is it negative or positive pressure? Even with the slight leak while I was adding coolant, my system went under negative pressure when the cap was removed when the engine was cold. Try to figure out whether it is blowing out or sucking in. Sucking in is a good thing.

You description of engine operation sounds very normal to me. A little loss of coolant isn't a hazard unless you fail to repond to higher than normal (typical) operating temperature or don't top up when necessary. A leaking water pump seal can sometimes take a while to reveal itself. It is highly unlikely that a pump seal will avalanche into a major failure (assuming that is what is going on), but there are no guarantees.

Sorry I can't offer more. vic
 
Last edited:

Altered Sprinter

Happy Little Vegemite
The dynamics of co efficiency between engine temperatures as to oil type and coolant don't always get along that well as to outside temperature V's inside engine temperature, thus a cooling system at times can struggle as to temps and oil pressure with especially elevations under varying loads, you don't have a thermostat that will compensate for both low elevation as to high elevations of operations, as engine and radiator give different readings under proven cooling system tests.

Vic said a water pump seal , could be it leaks under hi operating pressure but not at idle. if water is present it will run back along the side of the block and drip or show rust stains near the base of the oil breather pipe, at the same time look for oil weapage and built up grease at the same section the base of the alternator is another key as is the underside of the heat shield.
It may be a blocked radiator , engine coolant type they do have a life span, before cooling efficiency starts to degrade.Partially blocked fins in the front of the radiator,this can to a degree effect cooling at varying temperatures.

If in doubt where you just can't seem to find a reason as to coolant loss, then arrange for a hi-pressure test on the radiator and the head at the same time, if both pi pressures are in the green zone all is OK:thumbup: if one is green and the other yellow to red :shifty:then at least your locating where the hi temps are deviating from, and this can then be investigated further.Sprinters are a weird mob made by Germans not for American or Australian climates, as for a German air-con operation in tropical zones. you have to be joking.
:dripsarcasm::dripsarcasm:
Drip, drip , sizzle, sizzle.
 

autostaretx

Erratic Member
Is it negative or positive pressure?
It sounds like positive pressure (tried to bop him in the head)... so i'm voting for a compression leak into the coolant.
In a non-diesel, i'd say "cracked head gasket" (tiny, tiny crack), such that the 15 psi of the cooling system isn't forcing water into the cylinders.
It could be a broken cylinder head restraining bolt... the 300+ psi (and higher) of the cylinder can lift the head to pressurize the water, but the water pressure can't do the reverse.

My attempts to prevent the water from getting back into the cylinder are to explain lack of colored smoke.
The loss of water says it's going somewhere

One frequently can't see "smoke" from your own car... but someone following along behind sure can.

--dick
 
Last edited:

220629

Well-known member
...
One frequently can't see "smoke" from your own car... but someone following along behind sure can.

--dick
Missed that Bop in the head.

I've noticed that diesels also seem to share that pungent sweet odor of hot coolant burning in the cylinders should that be where it is going. FWIW. vic
 

talkinghorse43

Well-known member
You can buy a tester that will analyze the gas composition in the head space of the radiator and tell you if you have a leak of exhaust into the coolant. My son bought one from SnapOn for ~$100, but others are cheaper.
 

abittenbinder

Doktor A (864-623-9110)
Is this something I can just ignore? It's not causing problems now, I guess, but... is it going to cause problems later?
I would be curious to hear if your heater's performance is erratic. If you have not been operating the heater on a trial basis this summer, do so and let us know.

Doktor A
 

ron234

New member
It sounds like positive pressure (tried to bop him in the head)... so i'm voting for a compression leak into the coolant.
In a non-diesel, i'd say "cracked head gasket" (tiny, tiny crack), such that the 15 psi of the cooling system isn't forcing water into the cylinders.
It could be a broken cylinder head restraining bolt... the 300+ psi (and higher) of the cylinder can lift the head to pressurize the water, but the water pressure can't do the reverse.

My attempts to prevent the water from getting back into the cylinder are to explain lack of colored smoke.
The loss of water says it's going somewhere

One frequently can't see "smoke" from your own car... but someone following along behind sure can.

--dick
Thanks for all of these answers!

1) I found the water pump, and no white streaks or dribbles.

2) Wife follows the van in our car about once a week, and has never noticed white smoke (asked her earlier to look for it)

So... to check on broken cylinder restraining bolt or "tiny tiny crack" I would ask someone to do a HEAD pressure test?

The vehicle has 130,000 miles on it (answer to previous question).

I'm going to go drive around with the heater on to answer Dr. A's question about inconsistent heat now.
 

ron234

New member
Thermostat stuck shut
That causes pressure inside the radiator? How do I check for that?

Interestingly, I only drove about 20 miles yesterday... stayed at the same elevation... and this morning, I still had a decent amount of positive pressure blowing the cap off (although not as much as when I check once a week... that's like scary pressure!)

There is also a lot of GURGLING when I release the cap

Also interesting, there was more fluid in there today than when I topped it off yesterday.
The temperature was colder this morning when I checked than it was yesterday when I turned the van off.

Thanks for all this advice and help to everyone.
 

talkinghorse43

Well-known member
There is also a lot of GURGLING when I release the cap

Also interesting, there was more fluid in there today than when I topped it off yesterday.
The temperature was colder this morning when I checked than it was yesterday when I turned the van off.
These observations both point to a leak of air/exhaust into the coolant passages in the engine. The gurgling coming from gas expanding as the pressure is released and the increased level due to pockets of gas caught in passages and displacing volume once occupied by coolant.
 

ron234

New member
I would be curious to hear if your heater's performance is erratic. If you have not been operating the heater on a trial basis this summer, do so and let us know.

Doktor A
OKAY! I went for a drive and the heater worked torturously well and consistently :). Also, we have used the heater when we have had this problem and although we weren't specifically thinking about it, neither of us have ever noticed inconsistency in the heater before.

So... what does that mean?
 

autostaretx

Erratic Member
If the heater is working, the coolant is circulating. (i.e. pumps are working)
I haven't checked for the Sprinter, but many cars bypass the thermostat with the heater's fluid circuit (so it's a partial work-around for a stuck-shut thermostat).
A stuck thermostat should lead to excessive coolant temperature and boil-over with a half hour's driving (or less), so it's probably not a stuck thermostat.

If you know someone with a DRB=III, DAD or CarSoft unit (and probably AutoEnginuity), they can run a quick "compression test" (the unit looks for uneven resistance to the starter cranking the engine)... it may (or may not) reveal a leaking cylinder easier than a "real" gauged compression test.

--dick
 

abittenbinder

Doktor A (864-623-9110)
OKAY! I went for a drive and the heater worked torturously well and consistently :). Also, we have used the heater when we have had this problem and although we weren't specifically thinking about it, neither of us have ever noticed inconsistency in the heater before.

So... what does that mean?
I have seen several cases with similar post cool down latent pressure symptoms such as your Sprinter. Both involved slow coolant loss but both also had very inconsistent heater operation.

Coolant flow was compromised in both cases resulting in very low and erratic flow to heater core (confirmed by measuring flow into and out of heater circuit).

After ruling out any issues with radiator blockage, heater core blockage, water pump performance, thermostat, etc. I concluded a localized air pocket was developing in the coolant circuit due to possible cylinder compression inclusion into the cooling system.

Diesel combustion gases in coolant tests were negative.

One of those engines failed and I will be conducting an autopsy in the next few weeks.

Doktor A
 

Boater

New member
So despite missing some of the usual symptoms, do we think the OP should be getting a compression test and/or leakdown test to see if there is a problem with cylinder head integrity?
 

talkinghorse43

Well-known member
Since the symptoms could only be from a leak of high pressure air/exhaust into the coolant, I vote for a leakdown test of each cylinder to (hopefully, but the crack/hole could be too small to show up) pinpoint the problem area before engine teardown.
 

SewerRatz

Illinois Licensed Plumber
I have had some issues with coolant blowing off from the little overflow hose below the radiator cap. The radiator has been replaced a few weeks ago due to it having a split in the side, and ever since every few thousand miles I the coolant light lights up. I only need to add a cup or two of coolant to top it off. I tried a new radiator cap which is rated for 18 lbs., I was wondering if this cap might be underrated since I have seen 20 lbs. caps offered for the sprinters. http://www.oreillyauto.com/site/c/s...004&make=Dodge&model=Sprinter+2500&vi=1434747

I checked the coolant for oil and it is as clean as the day it was put in, I checked the oil, and no signs of water either. I know my electric water pump is not working, not sure if this would cause an issue. As for heat it blows hot all the time. Just one other note about a year ago my water pump had a leak at the shaft and sounded like a blender full of marbles so I replaced that and didn't have any issues back then.

2004 Dodge Sprinter 198K miles.
 

Trackbum

New member
I know its an older thread, but this is exactly what I'm experiencing with my 2006 2500.

I'm curious what the outcome was. Does anyone know?

Thanks,

Tom
 

jhaywood101

New member
Oct 15, 2016
Doktor A, I have a 2006 3500 with a 5cyc Mercedes crate engine with 15,000 miles on it. recently I have had the coolant level drop too, in fact I lost about a quart in 60 climbing miles last night, This morning when I checked there was significant pressure still in the system, enough to blow the cap out of my hand. I cannot detect any oil in the coolant, nor any coolant in the oil. There is some small amount of coolant around the drivers side of radiator, but I cannot for the life of me find a definitive leak, even with that high pressure build up. could the leak only show itself when the engine is hot? my new (300mile) radiator has all new hoses and tight hose clamps, and has a cap that says 20lbs, is that too high a pressure?

Thank you in advance for any help you my be able to provide.
 

Top Bottom