It's the Radiator cap! NOT Leaky Thermostat Housing.

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Jim Henderson

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After letting the car sit for a few hours I was able to get a better look at the leak from the thermostat housing.

Short answer is it is NOT the Tstat housing, it may be either a bad "Radiator Cap" or bad O ring on the cap. Or some problem with the hoses near by. The Housing is Most likely OK. I haven't 100% solved the problem but suspect the items mentioned above, or it is a waterpump issue, arrr. Need to confirm.


Long answer and a few corrections...

The "Radiator Cap" Does NOT have a spring loaded seal. Or else mine is busted and doesn't move. I am used to radiator caps with a spring seal, so I must have imagined that is what I was holding in my hand. There appears to be some sort of plunger inside the cap or else it is just a cavity in there for some purpose, it doesn't move. The O ring seems to be somewhat flattened I would guess from old age and maybe is not sealing fully. The inside of the tstat neck feels like somewhat soft rubber, the O ring seals against the inside of the neck against the rubber.

The Thermostat housing has a small 1/2" hot dog shaped hole on the inside of the neck which is supposed to be there. It is most likely a overflow vent for over pressure problems.

So I am guessing now that the O ring or cap are not properly sealing and is releasing water thru the vent hole and spilling onto the pulley and splashing around which is what left me clues that this general area is where the problem lies. So it is either the cap, nearby hoses or a leaky pump. I hope it is just the cap O ring since I have those at home and basically the fix is free.

Otherwise, I need to find the cap, which so far isn't on Rock Auto but the Cap adapter(Tstat Housing neck) is, strange they would have that, but I don't think I need it. Or it is the pump which goes for $40 to $90 depending on rebuilt, probably new china made or OEM.

I will probably replace the O ring this week and see if that works. Then maybe a new cap if it doesn't. Hope it isn't the pump, but so far no hard evidence of that being the problem. I need to either see it leak or crawl under the car to check the weep hole.

SO, I am either an idiot on a wild goose chase, or maybe I get lucky and fix this for cheap. Either way I'll post what I find.

Jim Henderson
 
This is not a "radiator" cap. The factory manual calls it the "engine fill cap." It doesn't have any pressure relief valve in it, and there is no "vent" from this area. (The pressure relief is in the cap on the reservoir by the windshield.)
Check the two small hoses that point up behind the cap. The spring clamp gave out on one of mine on my 04 and caused a small leak. I found it when I saw that the hose was about to pop off.
 
It's the COOLANT OUTLET PIPE. This is a black plastic dohickey that sits behind the thermostat housing and connects up all the hoses etc to the engine. Looks more like a plastic barrel with a couple pipes coming out of it. About the size of your fist with some pipes.


Long story...

This morning when I got to work I checked the engine right away and knew it was warm since the electric fan was on. I also heard hissing from the front of the engine. Before with the engine shroud on I could not see the area of the suspected leak. Now I could clearly hear it but still not see the leak. I saw a small hose(throttle body heater hose) had some moisture on it and looked a little rough. So I held my hand near by. A lot of air was flowing but I wasn't sure if it was from the fan or the leak. So I did the old bubble test... I poured some water near the suspected leak. It flew everywhere due to the air and or steam. BUT, it landed on the Coolant Outlet Pipe and I could see steam flying off the component and making bubbles.

There is an almost pefectly straight crack running from front to back, about 3 inches. Since the crack is black and the plastic is black and since it looked like a casting seam, I never spotted it before.

Steam is often invisible when escaping under pressure. Also very hot and can give a good burn so take caution if you try to locate steam leaks.

So looks like I need to call around, maybe one of the site sponsors to get this part. Hope it's cheap but suspect it is more than I would expect.

So unless there is another leak I didn't spot, this is the the fix. I would guess I will have it fixed next weekend after I get parts. Til then I fill er up with water and carry a gallon with me.

So for those with mystery leaks and the degass bottle wasn't it, this may be a place to look especially if you spot water drops ontop of the engine shroud and the air box between the radiator and engine.

I hate plastic parts under stress.

Jim Henderson
 
joegr said:
This is not a "radiator" cap. The factory manual calls it the "engine fill cap." It doesn't have any pressure relief valve in it, and there is no "vent" from this area. (The pressure relief is in the cap on the reservoir by the windshield.)
Check the two small hoses that point up behind the cap. The spring clamp gave out on one of mine on my 04 and caused a small leak. I found it when I saw that the hose was about to pop off.
Click to expand...

You are correct. I thought it was odd there might be two pressure relief caps. However, there is a vent on the inside of the throttle body. I would assume if pressure built up enough or the rubber seals failed, the water would vent thru the hot dog shaped hole.

Either way, as mentioned, this was not my problem, the Coolant Outlet Pipe is it.

Thought my blow by blow explanation might help some others who have similar mystery leaks.

Jim Henderson
 
Minor correction on my last post... I said a vent on inside of throttle body. I meant on inside throat of the Coolant Outlet Pipe, under the cap.

I now have one P/N 3W4Z-8548-AD in my hand. Be warned the part for the 2004 LSV8 is VASTLY different from the 2002. I assume somewhere in there, there was a part change, so make sure you have the right part for your model year.

The Seals look like rubber bands I hope they work. I would feel better with O rings, but maybe these rubber bands fit around a pipe and then seat in the channel. We'll see soon enough.

I will probably install tonight and then flush the engine and make a coolant change later this week.

For the time being, I am surprised how complicated this plastic casting is. Pipes within pipes etc. I am a little worried at the roughness of some of the inside casting seams. The outside is relatively seam free but you can barely see a seam right where my crack was, so definetly the seams are the weak point on this part, as usual with any casting seam. There are also two end plugs glued into the ends of the two side pipes, another potential failure point.

I really hate plastic parts for engines so excuse my critiscism here. The walls of this assembly are too thin in my opinion considering the heat, pressure etc this part is supposed to handle. Could just be my bad luck with this failure or could be a marginal design. Eyeball guess is less than 1/16 inch thick hard plastic.

I do not recall anyone else having this problem so I will assume it is just my bad luck.

When I get the job finished and road tested for a week I'll post more.

Jim Henderson
 
You are not completely alone. I have heard of one other person who's outlet pipe broke.
Yes, the gen II engine is a lot different on top than the gen I engine.
 
Well, I replaced the coolant outlet pipe and am now doing my usual commute and will be checking water level to see if it stabilizes after the bubbles work themselves out of the system. After my 30 mile freeway commute and letting it cool down, the fluid level was down about a quart. Could be bubbles getting out of the system or a small leak, but I did not see or hear any.

Once again, I hate plastic engine components...

When I removed the old Coolant outlet pipe I noticed the coupling pipe(I looked for drawings and a name but???) from the rear of the Coolant outlet pipe to the top of the engine block looked strange colored, kind of brownish. I touched the flange and about 90 degrees of the flange fell off. I hate plastic. The rest of the pipe looked OK, just the thin flange was brittle and discolored. To replace this pipe I believe the throttle body and the connection between it and the intake manifold should be removed along with other hardware. A much more involved job so I took a gamble in not replacing this pipe.

If I was smart and or had time, it was getting dark, I should have waited and bought a replacement for that pipe between the engine and the Coolant outlet, since I am sure the brittle feel of the plastic will lead to my next leak. But I took a risk since the face of the flange does not appear to mate to anything. The seal is made by the "rubberband" seal around the outside of this pipe and mates to the inside of the Coolant Outlet Pipe. It is a "sliding" fitting, as well as the other two small seals. So I figure the seal is still made as long as that piece of plastic doesn't fail and is improved when under pressure. We will see if I was foolish in not waiting for a new part. So far there are no visible leaks. If the coolant level stabilizes after a few cold/hot cycles I'll know if there is still a problem.


Comments about what I saw and did...

The coolant outlet pipe is definitely a pos on my car. The two small pipes to the throttle body hose and the degas bottle hose are both the same brown color, and I can break off pieces with my finger nail. Very similar to plastic that has sat in the sun too long. Even the inside pipe of the main chamber feels a bit squishy. This plastic part definitely did not hold up on my car. Could be overheating from the two times when I ran out of coolant, once I left the degas cap off, duh. The other time was last week when I lost a lot of water thru the crack.

Speaking of crack... The inside of the main chamber of the coolant outlet pipe had a hairline crack that perfectly matched the crack on the outside. So I definitely found the leak, it was not the fill cap or threads, it IS the body of the pipe itself that failed.

From visual inspection I would have said this was a half hour job, WRONG. Everything is easy to get at except the top driver side bolt on the coolant outlet pipe. There is a U shaped hose from the throttle body that gets in the way, a real pita during reinstall. I recommend either removing the hose, a pita too, or installing the bottom driver side bolt loosely and then working at installing the top bolt. A small 1/4 inch drive ratchet with extentions is handy, also an electric ratchet so you don't spend all day turning a wrench.

The other difficulty was removing the hose clamps. Those spring loaded clamps are a real pita to work with and in tight spots. I recommend replacing with worm gear type clamps in the future.

The rubber seals between the engine block and Coolant outlet and between the tstat housing and coolant outlet were in good condition so I reused them. The parts counter didn't have the two small seals but I did get the two large ones. I used some silicone grease to ease reassembly.


Well, this week I will check water levels after each drive. Then if all is well, this weekend I will drain and flush and then refill with coolant.

This job took me about 2.5 hours mostly due to hose clamps and that one bolt. If I replaced the other pipe behind the coolant outlet pipe I think it would be an all day lolipop. I probably will do this anyway if I plan to keep the car, not a sure thing.

Jim Henderson
 
Ah found a name for the mentioned pipe. It is ALSO called Coolant Outlet Pipe., duh...

from... http://deneau.info/ls/ under Description, Engine Cooling...

23 9N499 Coolant outlet pipe This is the one between the top of the engine and the other outlet pipe. The picture arrow from 23 points right at the flange, tiny picture tho. This slides into the back of #15.

15 8A504 Coolant outlet pipe This is the big outlet pipe between the T stat housing and the other outlet pipe.

Jim Henderson
 
joegr said:
The level shouldn't drop after a drive if you used the correct bleed procedure to get the air out.

http://deneau.info/ls/s6x~us~en~file=s6x33004.htm~gen~ref.htm#extract_142
Click to expand...

I have done a half 'a' bleed due to time involved. I will be doing a complete coolant change and a correct bleed this weekend assuming the leak is fixed.

I usually bleed and check and top up several times as needed every day for a few days until I am ready to do a complete coolant change. Then I do it again after changing coolant. I have done this with all my vehicles for who knows how long, just to be sure I didn't goof or miss something. Usually after the first day I don't find a coolant drop. I should know this possibly tomorrow.

Jim Henderson
 
Did I mention, I hate plastic engine parts?

Lost all the coolant this morning on my drive to work. Lucky I had two gallons of water on hand since I don't trust this car.

Another plastic part has failed with a crack. This time it is the Upper Radiator Hose PN 8260. Why is there a plastic Y in the middle of the rubber hose? Why can't the hose be separated from this Y so I don't have to buy a dealer specific part at inflated cost? Oh! Costs almost $80, I get it. Arrr.

Plastic, I hate plastic.

Anyway, I am going to assume this is a result of me having to remove this hose in particular in order to work on the rest of the system. Things are tight so you have to pull and twist it a fair amount, but nothing unusual in all my repairs of other cars over 40 years. It also might be a result of overheating 3 times in the last 6 months, twice this week. Heat might cause the plastic to weaken, duh who would think a coolant component has to stand up to heat. It's supposed to be cool right?

My opinion is that this part should not be plastic, it should not be in the middle of a hose and if it has to be plastic it should be stronger to stand up to normal service.

Oh well, off to the parts dept again. I wonder if the plastic Lower Radiator hose is next what with my luck on this part of the car.

Arrrh


Jim Henderson
 
Jim Henderson said:
Did I mention, I hate plastic engine parts?

Lost all the coolant this morning on my drive to work. Lucky I had two gallons of water on hand since I don't trust this car.

Another plastic part has failed with a crack. This time it is the Upper Radiator Hose PN 8260. Why is there a plastic Y in the middle of the rubber hose? Why can't the hose be separated from this Y so I don't have to buy a dealer specific part at inflated cost? Oh! I get it. Arrr.

Plastic, I hate plastic.

Anyway, I am going to assume this is a result of me having to remove this hose in particular in order to work on the rest of the system. Things are tight so you have to pull and twist it a fair amount, but nothing unusual in all my repairs of other cars over 40 years. It also might be a result of overheating 3 times in the last 6 months, twice this week. Heat might cause the plastic to weaken, duh who would think a coolant component has to stand up to heat. It's supposed to be cool right?

My opinion is that this part should not be plastic, it should not be in the middle of a hose and if it has to be plastic it should be stronger to stand up to normal service.

Oh well, off to the parts dept again. I wonder if the plastic Lower Radiator hose is next what with my luck on this part of the car.

Arrrh


Jim Henderson
Click to expand...

ive learned to except my v8 engine is about 58% plastic, lol
 
Well, the new Top Radiator hose is in now and the system appears to hold water under pressure. Yeah that's what I said yesterday.

Hardest part of the job was reusing the small hose clamp for the small hose coming off the Y(T if you prefer). I did not have a worm gear clamp of the right size so I reused the factory spring clamp. Because of the position and tight confines, it took me at least half an hour just to get this clamp in place.

Do yourself a favor, replace any spring hose clamp with a worm gear clamp anytime you remove an old clamp.

Otherwise the pipe replacement is straight forward. It helps if you disconnect the big accordion hose from the Throttle body so you can swing the air box out of the way to get at the hose.

The pipe had a nice crack the full length of the center section but somewhat at a diagonal. Water was literally spraying out of this crack so there was no mistaking this one. So at best guess, when I twisted the hose to remove it the first time, I may have stressed this piece of plastic. There is no discoloration and the rubber part is in excellent shape.

I will do my commute again, with extra water again and see if things hold up. IF all goes well, this weekend I will drain the plain water and possibly do a chemical flush and then replace with gold coolant.

I am a little nervous about chemical flushing this car since I am having bad luck with the plastic components. Normally I would do such a flush at 100K miles and sicne I am at about 90K now, this would be a good time to do it. But the system looks squeaky clean so I may just skip this part.

BTW, I also bought a new thermostat for the day when I get around to doing that. I will also replace the rear Coolant Outlet Pipe at that time since I do not trust the plastic parts any longer.

The thermostat is strange. It comes in two pieces and looks very little like any thermostat I have ever replaced before. It will be interesting to see how this part is assembled and installed. It costs $26.

Jim Henderson
 
hi im new here just bought a lincoln ls with overheating problems but i need to know what size allen key i need to remove that engine refill cap
 
I'm glad I read through half of this thread before I realized it's super old (saw someone was banned).
 
Gaboi said:
i need to know what size allen key i need to remove that engine refill cap
Click to expand...

well I've always gone with the method of starting with a big one and going down in size until i find the one that fits perfectly.
 
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