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98 SOHC Coolant leak

tchalm

Active Member
Joined
September 22, 2012
Messages
63
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City, State
Hillsboro, OR
Year, Model & Trim Level
98 Explorer XLT
My 98 4L SOHC has been losing coolant for several months.

Is it possible that coolant could be leaking from the lower air intake?

Do the lower air intakes manifolds tend to crack with age, miles and heat?

Thanks,
TChalm
 



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^^ +1 Do you see the coolant anywhere in particular?
 












Check the notorious lower thermostat housing first.
Probably leaking at the threaded sensors or seams.

If so, upgrade to the better and cheaper upgraded housing.

Dang, I love this forum!

There's an ugly hole in the lower thermostat housing to the left (looking from the front) of the thermostat. I haven't checked for cracks around the sensors yet, but I don't need to.

It's time to start gathering parts.

Thanks for the link to that other thread, which included the link to Ben Grosser's incredible write-up! With that info, the whole job looks very possible even for a duffer like me.

Three cheers and many thanks!
 






There is no coolant in either the upper or lower intake manifolds.

Thanks for that tidbit, too. Someone else said that there was coolant that ran thru passages in the lower intake manifold. That didn't make much sense to me, but I didn't know otherwise.
 






LOL, no surprise it failed. Also consider replacing the short bypass hose
while you have it off. Replacing it wouldn't be a fun on the road side. GL
 






So I'm shopping for parts. Knowing that quality can vary all over the place, I'd like to see something before I buy it. O'Reilly's has a kit made by Murray that looks like it's complete which I could go look at it; it's US$150. RockAuto has the kit made by Four Seasons for $111, but it's sight unseen. Judging by the pictures (there are no parts list) the kit has the upper and lower housing, both sensors and I'm guessing all of the gaskets.

Any thoughts on quality of either one? Or a better place to get it. (The parts guy at the local dealership is a parts genius, but the prices tend to scare me off.)

Thanks again.
TC
 






Unless it's suspension or brakes, I always prefer OEM replacement parts.
Check RockAuto or Amazon for pricing. The sensor clips are dealer only.
 






Are you just replacing what you have, or are you upgrading to the newer lower housing and push in sensors?
 






It seems to me that it makes sense to replace everything - including that short by pass hose. I don't want to have to do any portion of this job again. I have replaced the thermostat twice, and that's fairly easy - but the rest of it? I think doing it once is enough.

Thoughts?
 






Only a few parts are needed for a reliable long term repair.
Lower housing, both sensors and clips, and two o-ring seals.
Replacing the bypass hose is a no brainer, and it's cheap.
 






When I upgraded I used these parts

Motocraft RH144 lower housing Rockauto
Motorcraft upper and lower gaskets Rockauto
Motorcraft SW6146 temp switch Ebay
Motorcraft DY1004 temp sensor Ebay
Motorcraft sensor locking clips Ebay if you can find or dealer

I got the FourSeasons upper housing but the angle of the hose connector was off a just enough to make putting the hose on very hard.

I ended up using my old upper housing and it works great.

If you do this you might want to put a bread bag tie on the clips when putting them on. Easier to find if they decide to fly away while putting them on.

And new hoses.
 






When I upgraded I used these parts

Motocraft RH144 lower housing Rockauto
Motorcraft upper and lower gaskets Rockauto
Motorcraft SW6146 temp switch Ebay
Motorcraft DY1004 temp sensor Ebay
Motorcraft sensor locking clips Ebay if you can find or dealer

I got the FourSeasons upper housing but the angle of the hose connector was off a just enough to make putting the hose on very hard.

I ended up using my old upper housing and it works great.

If you do this you might want to put a bread bag tie on the clips when putting them on. Easier to find if they decide to fly away while putting them on.

And new hoses.
PERFECT!!! :thumbsup::thumbsup::thumbsup:
 






So, my son helped me change the housing last weekend. OK, OK, he did most of the work and I helped him a little bit. But it was fun hanging out with him - I don't get to do that enough anymore - he's 24 now and a great mechanic. I just wish one of the other kids was a doctor. Oh, well.

Thanks for the write-ups, the tips on the tricky parts really helped.

However, we had trouble with a couple of things that I don't recall having read about.

We removed the alternator, and wanted to remove it's bracket to get at the lower hose and little easier. Unfortunately, there's a bolt behind the serpentine belt tensioner that would not come out - it loosened up a bit, but then got really tight again. So we tightened it back up and gave up on that.

The next problem was that the sensor on the left wouldn't come out; it would turn, but the threads were locked up, so that turning the sensor just turned it's fitting too. After figuring that out, my son got a chisel and broke the lower housing around the sensor to get the sensor out.

Having an 8 mm end wrench ratchet would have really helped to remove the bolt behind the sensors. One write up says that an 8 mm universal socket would get back there, but I don't know about that. There are about 5 different cables and hoses in the way. Removing the upper air intake would help, but then you need to replace that gasket, too.

After getting the housing out of the way, we found a giant mess behind it - there was a rather large puddle of coolant underneath the lower air intake. So we mopped up as much as we could.

Then it took us a while to find the right order to install the lower hose. We ended up figuring out that we needed to put the hose on the lower therm housing first, and then slide the hose onto the fitting at the water pump. And that's where it would have been nice to have the alternator bracket out of the way.

After that, finishing up was fairly routine.

Judging by the build-up of crusty coolant on the housing, my guess is that it was the lower gasket that was leaking the most. And/or it was leaking at the sensors. And what I mentioned earlier looked like a hole in the housing, was really just the shape of the housing and the arrangement of dried crystals of coolant.

One thing that I hadn't seen mentioned before... fill the block with coolant before you install the thermostat. Just be sure to tighten the valve at the bottom of the radiator and put the radiator hose back on if you removed it.

One more thing, I got the parts kit from O'Reilly Auto Parts made by Murray. The sensors were the screw in type, not the clip style. The first one lasted about 13 years and 220K miles or so. I hope this one will go a while too.

Cheers! and Thanks Again for all of the help!
 






Well ... that part lasted less than 4 years. This time it got really serious really quickly and I did not have time to spend on diagnosing the rather nasty coolant leak. I took it to a local shop that has done good work for me before. They found the problem was that thermostat housing. $400 for parts and $450 for labor later my rig is back on the road. Ouch!
 












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