Engine - Coolant leak at water outlet housing | Ford Escort Owners Association (FEOA)
  1. Wash your hands and do not touch your face, keep it safe and clean. Long live Feoa!

Engine Coolant leak at water outlet housing

Discussion in 'ZX2 1998-2004 2.0L DOHC' started by MetalsGeek, May 7, 2019.

  1. MetalsGeek

    MetalsGeek FEOA Member

    Messages:
    11
    Likes Received:
    3
    Trophy Points:
    253
    2001 ZX2
    78K hard miles (all short, around town)
    Original Owner

    This posting is similar to the excellent one done by "paul01zx2" back in 2011. It seems his photos have been deleted, so I thought I could replace one or two of the more interesting ones for those of you with this same problem. My wife's 2001 Escort ZX2 recently developed a leak between the cylinder head and the black plastic water outlet housing on the driver's side of the engine. This failure is apparently VERY common on the DOHC Zetec engine, and IMHO the primary cause is swelling of the rubber sealing ring over time. The rubber swells to the point where its volume becomes greater than the volume of its groove, and it eventually ruptures the thin inner wall of the water outlet housing. Without this support, the rubber distorts even more and pops out of its design location. In my particular case, the engine would lose an ounce or two of coolant when cold, but system pressure would eventually push the ring back into place and re-seal the leak when hot.

    In this photo of the failed housing, the rubber sealing ring stuck to the head (left) with visible distortion on the upper-left side. The housing (right) shows a complete detachment of the inner wall of the groove from 10 to 4 o'clock. The swollen rubber ring is now much larger than the groove.

    RH154 Fail.jpg

    Here are the parts you might consider ordering before you start draining coolant, with a couple comments for your reading pleasure:

    The Motorcraft RH154 Water Outlet Housing ($33 at RockAuto as of 5/2019) is essential. This part includes the rubber sealing ring at the cylinder head; you can see it in online photos of the new part. Some people recommend changing this to the 1998 version, but I did not do this. Aside from the fact that my wife likes to keep everything "original" (yeah, she's a purist) this would have required that I also replace the two coolant temperature sensors with their threaded versions. I figure that by the time this housing fails again in another 15 years, this car will no longer be my problem. Besides, the next owner would thank me for keeping it original... I found that a small wire brush did the best job of cleaning the corrosion pits on the aluminum head, and a small flat file removed any protruding areas. Slip the lower front port of the new housing into the bypass hose before bolting it to the head. A 10mm deep socket is ideal for all 3 housing-to-head bolts; torquing gently to 10 ft-lb is all you need to compress the sealing ring. Install the thermostat & sensors before you mount this housing on the engine.

    Since you have to move the thermostat over to the new housing, you should get a new rubber sealing ring; Motorcraft RG632 or RG633 ($5). Both of these are essentially a fat O-ring with a groove on the inside that fits over the edge of the thermostat mounting plate. The wider lip faces the outlet pipe (elbow). I used the RG632, and I think paul01zx2 used the RG633. They are quite similar; I think either one would work (neither is the housing-to-head seal). You'll need to re-use the special self-tapping screws on the outlet elbow (Torx T25) just snug.

    The thermostat is a Motorcraft RT1150 ($6) which is set for 190F. I bought a new one but the old one was still fine. I really like the clever design where the inner plate closes off the bypass port to force ALL coolant thru the radiator when the engine is hot.

    The thermostat outlet pipe (elbow) is a Motorcraft RH86 ($13). Some people have reported pinholes but mine was in excellent condition and could be reused. Just clean up the face where it seats against the rubber thermostat ring.

    There are two coolant temperature sensors in the housing. The one on top is a Motorcraft DY884 (Grey connector, for ECU, $19) and the one on the bottom is a Motorcraft SW6146 (Brown connector, for gauge, $20). In my case, the rubber O-rings on the old sensors were flattened from age and did not seal in the new housing. I didn't have time to shop for new O-rings and didn't want to spend $50 on sensors, so I removed the O-ring from each sensor and put a few wraps of Teflon tape in the bottom of the O-ring groove, then replaced the ring. The Teflon tape expanded the old O-ring firmly against the housing and sealed just fine. The old retaining clips can be re-used but new ones are available from Dorman as #800019 (2 for $4). Install the sensors in the new housing in the same orientation so the connectors will line up, and do all this on the bench before you bolt the whole shittenkaboodle to the engine. Consider which direction for the retaining clips so you can get them off later if needed. One of those 4-finger claw type grabber / pickup tools is the cat's meow when installing a clip on the lower sensor with the housing in place.
    zzyzzx, denisond3 and Joey_Twowagons like this.
  2. Defunct SR Owner

    Defunct SR Owner FEOA Member

    Messages:
    37
    Likes Received:
    14
    Trophy Points:
    18
    Good write up. I eventually replaced the housing on both of my cars with the 1998 housing as I prefer threaded sensors and pipe dope to the O-ring type that eventually leak. I also keep an original Ford thermostat to show auto parts suppliers what I'm looking for, as more often than not they try to sell something not suitable.
  3. MetalsGeek

    MetalsGeek FEOA Member

    Messages:
    11
    Likes Received:
    3
    Trophy Points:
    253
    Did your 1998 housing accept the same RH86 outlet pipe? (Assume so)
    I wonder if Ford has improved the rubber compound on the new housing seal so it won't swell up like the old one did. (Time will tell)
    I may soon look into trying to identify a standard replacement O-ring that will fit those sensors, but so far my cheesy fix is holding well. This info would be useful for people, I think. Perhaps someone else on FEOA has done this work already? My box of standard replacement O-rings did not have one with both major & minor diameters that fit.
  4. 4cylinder

    4cylinder FEOA Member

    Messages:
    708
    Likes Received:
    127
    Trophy Points:
    193
    Location:
    san diego, ca
    i still recommend upgrading to the 98 style over the newer style. All the issues described in this write up do not apply to the 98 style.

    the 98 style is plug and play upgrade for all zx2 with no issues

    the plastic for the newer style has too many issues and they crack and separate all the time. The newer style also tends to leak at the sensors

    the only upside to the newer style is that sensors can be replaced simply by removing a clip. Unfortunately for the owners with the newer style they remove the thermostat housing to change the sensors then install the clips the wrong direction. doing the sensor replacement this way also subjects the housing to movement at the head further subjecting the part to cracking and breakage compounding the main issue these have. This is why all my personal cars have been switched to the 98 style
    zzyzzx likes this.
  5. MetalsGeek

    MetalsGeek FEOA Member

    Messages:
    11
    Likes Received:
    3
    Trophy Points:
    253
    I kinda agree with you on all that. How is the seal at the cylinder head different on the 98 housing? Perhaps they used a "real" O-ring made of a compound that did not swell. I have seen similar issued on the ZX2 vacuum hoses, where the molded rubber ones fell apart at 15 years and the straight ones were still going strong.
  6. steve60tuesday

    steve60tuesday FEOA Member

    Messages:
    36
    Likes Received:
    17
    Trophy Points:
    18
    After discovering a coolant leak a from my thermostat housing a couple years ago, from one of the temperature sensors or a nearby invisible crack (?), I decided to swap it for the '98 version at the advice of 4cylinder.

    I replaced:
    Thermostat housing, RH43
    Temp sensor 1, SW5157
    Temp sensor 2, DY1144
    Outlet elbow, RH57
    Thermostat, RT1150

    And possibly additional O-rings for which I don't have a record. It's been a while.

    It took me like 6 tries to put it together right. There was a defect in the casting of the thermostat housing, and I had to re-cut the o-ring groove on a lathe. But this was probably a unique defect that is not the normal experience, and if I knew what I was doing, I could have just exchanged the defective part. But I wound up with a very well flushed coolant system due to 6x refill cycles, and I learned a lot about how to mount really awkwardly shaped things in a lathe.

    The housing and sensors have worked flawlessly ever since. And despite my troubles, I have to agree, the '98 housing is an overwhelmingly better design.

    Also, if you are into home and automotive maintenance, you can buy sets of O-rings for pretty cheap these days, like <$100 for an extensive set of <2" dia. rings. There are multiple material types like natural rubber (Buna-N), Viton, and Silicone. And there are very basic guidelines to select which material(s) work best in each application, based on temperature and chemical exposure. But these sets very quickly pay for themselves, and it is nice to almost-always have a fresh O-ring on hand when fixing a leak or rebuilding an assembly.

    Finally, not to get on a high horse here, but teflon tape is not a sealant. It is a lubricant for interference threads (e.g., NPT), and in such applications, the threads themselves form the seal -- not the tape. Adding thread tape to anything other than properly tightened interference threads is an incorrect use of thread tape.

    That said, if you can fix a leak by adding teflon tape, then more power to you. I've done it too. Thanks for a well-written contribution to the forum.
    zzyzzx likes this.
  7. MetalsGeek

    MetalsGeek FEOA Member

    Messages:
    11
    Likes Received:
    3
    Trophy Points:
    253
    I grant you that no thread sealant should be used to fill in excessive gaps, but the realities of real world tolerances in thread forms mean that a reliable gas-tight seal needs something to fill in those tiny gaps. I think we'll have to agree to disagree that Teflon tape is simply a lubricant. I've only used the taper attachment I made for my lathe twice, and my thread form was never textbook perfect but always sealed fine (with tape).
    Perhaps we CAN agree that my cheesy use of Teflon tape to expand an old O-ring would only make Scotty Kilmer proud... (grin) but when the car needs to go back into service NOW, you do what it takes.
    I've not seen the '98 housing in person but the photos seem to indicate that the seal against the head looks quite similar to the later version. Does it have a real round-section O-ring instead of the rectangular-section one I used? I still think the main cause of my failure was swelling of the rubber over time from poor QA or chemistry.
    IMHO Ford's vacuum hoses suffer from the same problem: special molded hoses rot much faster than mass-produced straight vacuum hose.

Share This Page