Coolant leak pressure question

[wesalexleft]

Ive been losing coolant in a 2003 Mounty 4.6L. Pressure tested and found a small leak at the intake manifold so I replaced the intake manifold gaskets. Still losing some coolant somewhere, so I've added dye and I'm pressure testing it again today. I'm losing very little pressure at a rate of 1 pound over 1.5 hours. I've kept the tester pumped to 15 pounds to try and expose the leak. I've been thinking a small leak in the heater core, but no visible signs on carpet, etc. My question is how long should it maintain pressure under a pump, indefinitely? It's dropping so slowly, as to not show a leak. Can anyone think of a leak that would only be present when the engine is running?? I've had it under pressure for 10 hours now and the fluid level is the same. We just drove it last week for about 500 miles, and lost about 1/4" in the degas bottle during the drive.

 

[HiImBrian]

Look for white smoke out of your tailpipe, it could be burning. Also check your oil for coolant.

 

[wesalexleft]

No white smoke or sweet smell from the tailpipe and no combustion gases in the coolant tank. I've been all over it once with uv light and didn't find anything, so I'm starting over with checking it again. Oil looks good on the stick, and just a little sludge under the cap, but nothing major there. I haven't opened the tranny to check it, but it's shifting well.

 

[wesalexleft]

Overnight update: I pressurized the cooling system to 15 pounds last night before bed at 11:45PM. This morning at 06:30AM the pressure guage was at 13 PSI. No puddles under the vehicle, and the degas borrow seems to have lost approximately 3/8" of coolant. No time to look into other signs this morning, and I'm hoping that the drop is due to the block cooling completely overnight. I've set it back to 15 PSI and will chek it again at lunch and again after work. I guess if this continues, a compression test will be next. Any thoughts?

 

[Exproblems]

Overnight update: I pressurized the cooling system to 15 pounds last night before bed at 11:45PM. This morning at 06:30AM the pressure guage was at 13 PSI. No puddles under the vehicle, and the degas borrow seems to have lost approximately 3/8" of coolant. No time to look into other signs this morning, and I'm hoping that the drop is due to the block cooling completely overnight. I've set it back to 15 PSI and will chek it again at lunch and again after work. I guess if this continues, a compression test will be next. Any thoughts?

You have the V-8, I have the V-6, so I'm not sure what kind of set up you have, but check the lower t-stat housing as the source of the leak since you've found no loss of coolant in any of the other area's mentioned by others. Back in mid-winter, I noticed I was losing a small amount of coolant very slowly every few weeks or so (10 ounces or so from the expansion tank). Never saw steam or coolant coming out of anywhere or on the ground until I looked towards the rear of the lower t-stat housing and saw a small amount of dried up greenish crud on top of the intake manifold behind the lower t-stat housing. I figured the green crud was from coolant but still not sure where it came from and the week before last I checked the area behind the lower t-stat housing again for leakage and saw a larger amount of coolant this time, basically a puddle of it. I now could see where it was leaking from and it was leaking from the lower t-stat housing at the "upper seam line" in the housing, it must have split there for some reason, front and back. I replaced the housing last week along with a new temp sensor and everything is good, no more leakage.
The housing I bought was from Advance Auto Parts, Dorman OE Solutions Part #902-860. It comes with a new t-stat and seal, plus the intake manifold seal already installed. You just have to re-use your 3 manifold bolts. It cost $84.99 but I used a $40 off coupon on a $100 or more order from www.couponcabin.com Dorman claims they have corrected the leaking and cracking problems of the Ford housing with their product, so I went with it since I know a new Ford housing could crack again. No problems with the fit or getting the new temp sensor to seat properly. Also, The Dorman housing comes with 2 sensor ports, but they give you a plug and a retaining clip to seal one of them up if you only have one sensor. I have one sensor. I also bought 2 gallons of full strength Peak Long life antifreeze($14.99 ea.) and the temp sensor ($16). Just something to look into since the leak I had started off very slowly and took a few months to progressively get worse and show more signs of a heavier coolant loss.

 

[wesalexleft]

Thanks much for the very detailed reply. I did replace the intake manifold when I replaced the intake manifold gaskets last fall just to be preventative. The V8 has an all-aluminum coolant crossover and is less likely to leak than then V6 I believe...at least mine was.

 

[Exproblems]

The V8 has an all-aluminum coolant crossover and is less likely to leak than then V6 I believe...at least mine was.

So the V-8 doesn't use a "plastic t-stat housing" as in the V-6? Just curious for future knowledge.

 

[HiImBrian]

So the V-8 doesn't use a "plastic t-stat housing" as in the V-6? Just curious for future knowledge.

Ford used the plastic crossovers in some of the earlier models of the V8. All of the late 2003 and up had the aluminum crossover I believe.

 

[xlt03]

Check your water pump weep hole. It's on the TOP of the pump. Make sure there isn't any snot (crude) in the hole. Also get underneath vehicle and look up at the front crossmember for crud drips. If you see the crud it could be your water pump. I had similar problem as you did but did not have a pressure testerto pressurize system. Did not have drips on floor but Iit likely evaporated before hitting ground. Also check that radiator hose clamps are actually clamping the hoses. I had one break but at first glance it looked ok. Closer examination show it didn't clamp and I had a leak. Replaced clamp and coolant loss stopped. In my case the water pump and clamp failure was at two different times. Hope this helps.If

 

[wesalexleft]

Update and advice needed. So I left the truck coolant system pressurized for about 24 hours while the engine was cold to find any leak for the cooling system thinking possible heater core leak. The pressure dropped from 15PSI to 13PSI, but always leveled off there. I'd raise it back to 15PSI and it took about 2 hours for it to drop back to 13PSI again. After leaving it this way for about 24 hours, I'd lost approximately 1/2" of coolant from the degas cannister. I then started the truck and had some white smoke from the tailpipe for just a minute or so along with some water from the condensate water from the tailpipe. Now I'm thinking head gasket. Any thoughts? I'm losing coolant with no visible signs, but do not have white smoke from the tailpipe normally. I think that 24 hours of pressure forced coolant into a cylinder, and at startup, it burned it off, but that during running, it's not enough to be visible. I don't see any signs of coolant in the oil, but I'm going to order an Oil Analysis kit to be sure. In the meantime, what am I looking at for a cost to replace the head gaskets and timing cassettes at the same time?
Also, any other possibilities? I've just replace the intake manifold gaskets in the past 6 months. The truck is running fine with the exception of the coolant drop which is slight but confirmed.

 

[wesalexleft]

Is it possible for the oil cooler to leak coolant into the oil? The V8 has coolant circulating the oil at the filter. I haven't seen a diagram for one, but wondered if coolant could leak internally a small amount and get mixed with the oil. I don't have milkshake oil on the dipstick, but still trying to trace this small coolant loss. This would be better than a head gasket.

 

[HiImBrian]

Is it possible for the oil cooler to leak coolant into the oil? The V8 has coolant circulating the oil at the filter. I haven't seen a diagram for one, but wondered if coolant could leak internally a small amount and get mixed with the oil. I don't have milkshake oil on the dipstick, but still trying to trace this small coolant loss. This would be better than a head gasket.

Yes that gasket goes bad quite frequently. It's the oil filter adapter housing and its a bit of a pain to replace. Not nearly as bad as a head gasket though.

I had a coolant leak from the black vacuum plunger that runs along side the passenger valve cover. Also from the back of my water pump under the intake manifold. Replaced that with a high heat rubber hose and clamps when I installed my Bullitt intake. Both very small and would evaporate almost instantly.

 

[wesalexleft]

Working on this again today. There are NO visible leaks outside the engine, and after keeping pressure on the coolant for a day, I did get coolant in the oil. I just did a compression test and the pressures are 165 on the high end and one cylinder at 150 with a few cylinders in between, so I think compression checks out. I drove to get the engine to temp and i did get some white sludge at the valve cover filler neck, along with some steam from the opening. i opened it just after shutting the engine down. I'll be doing a leak down test after lunch. Anyone have any ideas on how I'm getting coolant in the oil? No oil in the degas bottle that i can see. I did intake gaskets about 6 months ago, so they should be fine. I would think that an intake or oil adapter gasket would show outward signs of a leak if coolant was getting by one gasket and then into the oil gasket ring as well. I've seen a few comments on a freeze plug, any way to inspect/test without removing the front timing cover?

 

[cjohnson85]

Did you ever find your problem? I seem to be having the same issue ..we replaced head gaskets already now thinking freeze plugs?

 

[wesalexleft]

Still losing coolant to the oil

Sorry, but I think you're farther along than I am. Did you have a shop do the head gaskets? The shop should have noticed the freeze plug leaks behind the timing cover while doing the heads though, right? From what I've seen, each head has a plug, and the block has some too, all behind the timing my cover on the V8. If any of these leak, I believe they would then drain into the oil pan. Any other freeze plugs would be visible from outside I believe, and not mix with oil. It's either that, or a cracked block. I know there's one person on here with a thread where it ended up being the block. That's what I'm afraid of-spending big bucks on heads, and then find out that it's still not fixed.