Hey fellas,

Well my fiance had to take my truck home from work today as her POS 2008 BMW X5 (the least reliable of the vehicles we own....others being a 30 yr old Jeep Wagoneer XJ and my 25 yr old Ford with 300k...) Anyway, as she pulls into the driveway this evening, just after she shuts off the engine, steam starts rolling out from under the hood. I quickly pop the hood and see coolant boiling in the overflow and steam/coolant blowing from the radiator cap. After letting the steam abate some I popped the cap off and let the rest rush out...wasn't much more.

What could have caused this? I've had zero, zilch issues. She says she didn't do anything wrong and was just driving it normally. I switched the ignition on and the temp reading was up at the "H" (as if I didn't expect that). She's not at all a car person, but it's hard not to be angry with her...so I'm taking a break and writing this...though I don't think one needs to be a gear head to read gauges......*deep breath*...

Ok, so now what? Wait until it completely cools, of course, but fill it back up and change the oil/filter? What else? New thermostat? New Radiator cap?

I'll go dig a roughly human shaped hole in the backyard while cooling down and waiting for replies...

Thanks fellas,

S/F,

-Matt

 

I just started having the same problem with my just rebuilt 5.8l... NEW Motorcraft waterpump, 1 year old heavy duty radiator, new 4 seasons severe duty fan clutch, new stant cap, new Motorcraft factory thermostat, all new hoses, even a Motorcraft belt! Driving me nuts! I replaced the cap because it was blowing out- I had replaced it last year, with the new radiator, so I just replaced it when I put in the engine... Is it possible for a new water pump to break, and be able to check it without removing it?

Thanks for letting me piggyback...

Scott

 

Now that you've cooled off by digging the grave (just a simple rectangle will do), the next step I would suggest would be to remove the thermostat and test it by suspending it in a pot of water on the stove. It should start to open at around 170 degrees or so, and be fully open by 190-195 degrees. I would do this before anything else because overheating can damage them anyway, so why not test the most likely culprit. Of course check belts, water pump wobble and hoses. Oh- and don't bother with the pentagram and the holy water. She can't be that evil.

 

Seems unlikely but maybe one of the other pulleys locked up and none of the accessories were driven for a time on her way home.

 

Unfortunately, blowing out of the overflow is a tell tale sign of a leaky head gasket.

Fortunately, that's a good excuse to upgrade the heads.

 

When you shut off an engine the latent heat in the engine heats things above normal up as the coolant is no longer being circulated to carry away the heat.

So with the engine operating at higher than normal temps when it was running then when it was shut off the latent heat caused the boil over.

There is no need to be mad at her it is nothing she did. Might have to eat some crow and spring for a dinner out over that

Ok Possible causes from most likely to least likly

Thermostat, The Tstat could be starting to fail and opening late or not fully opening. The temp rating on T-stats is when they start open. If it is a 192F stat it will start to open at 192F . The temp rating is not when fully open but when they start to open.

Rad Cap, If the rad has started to fail it may not be holding the proper pressure in the system. We all know as pressure increases so does the boiling point of liquids. This allows the coolant to get much hotter before it boils this also increases the BTU's the coolant is capable of absorbing and in turn can release in when heat exchanged in the rad. A failed rad cap will reduce the amount heat the coolant can carry away from the engine and lead to over heating and boil overs.

Good rule of thumb when you replace the T-stat replace the rad cap.


Fan Clutch The fan clutch may have failed not allowing the fan to engage at the appropriate temperature. To check get engine to operating temp and turn on the AC (if equipped)the extra heat being shed from the AC condenser will usually almost always cause the fan clutch to engage. Other wise just let it run till it heats up, then shut the truck off then turn to run (do not start) and wait to see the temp gauge rise *(usually 5 to 10 mins) then start the engine the fan clutch should be engaged as coolant temps will be well above normal.

Radiator blockage. The rad could partially plugged and in need of a flush or replacement. you should be able to see the condition of the core if you drain some coolant from it and look down the rad cap any deposits on then ends of the tubes indicate restriction.


Accessorybelt, Slipping or failure, self explanatory

Water pump, failure due to partial seizing or impeller erosion.

Coolant, make sure correct coolant and between 50/50-70/30 mix.

Timing issues. Timing out of spec.

Head Gasket, Failure, start the truck when cold with the rad cap removed any air bubbling in the rad's coolant indicates a failed head gasket.

Air Fuel Ratio AFR out of spec.


Hope this helps

Matthew

 

Thank you all for your wonderful replies. Because of everyone's input, and the fact that my initial post could be used as evidence of premeditation, my fiance has been released from guilt

Seriously though, I sincerely appreciate everyone's assistance. Matthew especially, thanks for the detailed response.

So after a few hours last night I went out and refilled the radiator with just water and started up the truck again. All accessories are spinning freely and no wobble on the water pump. I still plan to change out the t-stat, radiator cap, and oil/filter. I just replaced the distributor and timed it properly with a timing light a few weeks ago - though it probably isn't a bad idea to check it to ensure nothing slipped.

Just to be sure:

We want a 190 degree t-stat and a 13-lb cap right?

 

Before you spend money, check into a hydrocarbon test for your coolant. It'll tell you if you need a head gasket....also....don't forget to inspect thoroughly at the head and block decks to make sure it's not visibly leaking.

 

That's the funny thing with mine- The engine was just rebuilt, all was well, new everything, but it seems to be coming out the radiator cap: and I noticed the reservoir was low(down at bottom, below "COLD FILL" line, yet the rad was full- So I brought the res. back up to the line, and THEN it started spewing... And, when I checked it last night, after cooling, reservoir was still full, but the radiator was down about 1/2 gallon or so...(About 4-5" below filler neck)

I am wondering is perhaps the pump(Motorcraft) failed, or the new thermostat(Motorcraft!) failed... The radiator has been working fine until now, although I did notice a similar blow off(but not to major proportion before the rebuild- but replaced the cap, and it seemed to cure it. But two caps in 6 months?

I may have to take this one to the radiator shop guy...

Scott

 

Good idea. I'll look into that.

I did start it up and run it for awhile last night. I didn't notice an undue amount of bubbling, just the normal few little microbubbles from it burping the system. I think I may have gotten lucky with it, but it doesn't hurt to double check.

 

Another thing you can do is rent (actually purchase and return) a cooling system pressure testing kit at the local Autozone or equivalent. If it leaks down, and you can't find an external leak, then you may have a head gasket issue. I would still test that old t-stat so you you can eliminate it from the list of suspects.

 

Well, I just gave mine another "Poor man's stress test"- first I checked the solution(not quantity) of the antifreeze- It is a little low, but not bad: But- when I put the cap back on, I noticed one of the lock tabs did not sit quite right, and was actually loose, while looking tight... I wonder if perhaps it had that issue yesterday(I had removed the cap to check the radiator level) when I replaced the cap, and so it vented early... Also, I realized that when I topped the radiator last night, the reservoir had a bit more than "Cold Fill" in it- as if it had taken the overflow, but not returned it when it cooled, as it is supposed to... I corrected the cap, and then pulled the overflow hose from the fill neck, and drained it into a bottle, until it was just below the proper "Cold Fill" line: As I had topped the radiator, it should be about right for capacity. Took her for a run, and while the needle did go a few widths beyond the halfway point of the gauge(unlike yesterday, when it was all the way Hot) I was able to catch the thermostat opening, and saw the temp drop. It stayed in that range for the trip- I also cut in the A/C to increase the heat load across the radiator: no change. So all seems to be back to normal. One question remains- I remembered that when I last replaced the fan shroud, I removed a 1' or so section from the bottom of it, to assist in facilitating its replacement with the fan etc. in place: This way it spreads around the fan assembly, and removes a big fight.(I have the narrow radiator shroud on the heavy duty radiator) Does anyone think that making a fill panel to cover the gap would be a bad idea?

Scott

 

[QUOTE=OldGoldie;17097890]

I think I may have gotten lucky with it, but it doesn't hurt to double check.

You know it is not self healing so I wouldn't buy any lotto tickets just yet. Also I can assure you that you loaning her Goldie was a good deed and they do not go unpunished.

Number one on the most/least likely list was the thermostat and rad cap. I would get those and some 50-50 antifreeze and run it to a real operating temp and see if you are good for the next lotto. I hope so as I like Goldie.

 

Total WAG, but make sure the timing indication is correct. OP mentions replacing distributor, just prior to the late unpleasantness. It was pointed out earlier, retarded ignition timing will cause overheating.

 

[QUOTE=sandymane;17098464]Self healing - I should only be so lucky!

So I have the rad cap and thermostat on order. I didn't do a complete flush yet (waiting for the therm/upper hose to come in). But I have changed the oil/filter and filled the her back up with water. I've driven in a solid 30 miles since and haven't seen it climb up past the middle of the gauge since.

So here's what I'm thinking - Jen can't drive stick worth a damn and/or doesn't know when to shift. That's all I can figure. I'm still going to change out the thermostat and cap, for good measure...but hell, I kind of have to chock this issue up to "driver error".

Scott, I don't think the gap in your shroud is causing the problem. The PO of my truck hacked mine to pieces and the bottom is held on with (now, because I changed them) metal zip ties for the time being. I've had no issues with the temp prior to this little Jen-driving-it fiasco...I'd guess that your radiator cap wasn't sitting right and you were losing pressure.

I'm definitely going to check it again. I'm heading to Africa for a couple of weeks this Friday for work, but I'll definitely check it again once I'm back.