Should I replace intake manifold/head gasket on Town Car?

Figured I’d ask experts (I am not one).

My hobby is buying older cars (previous limousines) and working on them to keep them running until it’s no longer cost effective. (i.e. Transmission goes)

I just bought a 1997 Lincoln Town Car for all of $1 (one dollar). It has 419,000 miles on it. (This is my low mileage car. My '98 Deville has 575,000)

I have maintenance records on it since it had around 100,000 miles. As my company was going to retire it from the fleet next month, they stopped doing certain maintenance back in November.

They were told by a mechanic that it needs a catalytic converter and 2 oxygen sensors. When they finally retired it into my hands, it had stalled at a stop light, would start but not keep it running unless flooring it, but it would die when they let up on the gas. It was towed to a mechanic and started right up there and ran fine for the 20 or so minutes they idled, drove, and tested it. Since they had scheduled it for retirement, they decided not to do any repairs.

To be safe, I forked over the buck and towed it to my house. I’ve idled it off and on for 1/2 hour at a time and it idles smoothly. Revs smoothly. I did see P0401 (EGR) and P0420 (catalyst) codes which were read as soon as I got the car home. I have not driven it around yet.

I noticed the coolant went down a 1/2" or so since I got the car a few weeks ago and was concerned that the head gasket was blown. After discussing previous issues about the car with the previous owner (my boss), I found out that there was also a leak in the intake manifold (leaking coolant) and it was epoxied twice in the last year or so. (BTW, this intake manifold was replaced with the newer version in 2006). He suspects it’s leaking again. (Haven’t looked closely yet at it but I do see where the “fix” was made.

I figure I’m willing to invest $500-1000 to get it running well and probably plan on using it for another couple years. The body and interior are in like-new condition.

SO, I have a couple questions. I can get a brand new intake manifold for $165 (again new updated version). I read through what’s involved to replace it and don’t see anything more complicated than when I replaced the starter on my Deville and also had to pull the manifold. Should I replace the intake manifold (getting rid of a potential coolant leak and some other leak that may be causing other problems)? And if so, it looks like there’s not too much additional work to pop the head, so do you think I should also replace the head gasket as long as I’m so close, as preventive maintenance?

Finally, what do you think the chances are that if there IS a leak in the intake manifold, it might cause the emission related issues I’m seeing, or do you think one or more oxygen sensors, EGR valve, and/or catalyst is also bad? I know if you’re burning coolant through the system it’ll eventually take out the catalysts so maybe it’s bad everything now.

Yeah, I know when I get cars like this anything is possible but I actually enjoy working through the problems and doing the repairs in my spare time. It’s therapeutic!

Thanks for any input.


I’ve never considered replacing a head gasket under ‘preventative measures’. If it is good, leave it be. Also, are you sure the intake manifold is where the leak is? I understand that there is a history of leaks with this car, but until I have definite proof I just don’t believe in ‘exploratory surgery’ with ‘disposable’ cars like this. I define disposable as anything with high miles and practically no resale value. Run them until they break something expensive, then have it hauled away. At the rate this is leaking coolant, it could be a little while before the leak is observable. By then, something big might just break.

As for the ODB-II codes, P0401 is for EGR Insufficient Flow. This means the EGR pipe and valve are clogged with soot. This code should not return when you clean them out. P0420 is for Catalyst System Efficiency Below Threshold (Bank 1). This could mean a bad cat or bad readings from a worn secondary O2 sensor. A direct fit cat system is $209-$229 at, and the O2 sensor id $65.00. I’d try the O2 sensor first. Then worry able the cat if that code returns.

Lastly, with the stalling you had already experienced, have you replaced the fuel filter yet? That just may be the problem. The ODB-II system does not monitor fuel pressure, and sets no codes. Just a hunch.

Thanks for the input. BTW, the engine is a 4.6 OHC Vin W.

Yes, I do consider this a disposable car. I donate my oldest car as something else comes up. My '89 Grand Am is going this week. I also consider them to have no value and don’t donate them as a tax writeoff… just to get rid of them and maybe help somebody.

Anyway, the current fuel filter has 43,000 miles on it and I actually just bought a new one earlier today. Will be installing it Thursday. Have not cleaned the EGR valve yet but did buy a gasket in preparation. I tested it with a hand vacuum pump and it holds a vacuum and sounds like the diaphragm compresses ok. There’s no opening to feel it. The EGR valve has 83,000 miles on it. I’m going to clean the pipe and pintle, etc. also Thursday. Glad to hear you think this might be the cause of that code.

Pretty sure there are 2 cats, 2 pre-cat O2 sensors and a single post cat sensor. I think you’re suggesting the post-cat sensor. When I changed the oil (no coolant in the oil), I glanced at the exhaust system and from what I remember, the cats go into a Y, and then in the single exhaust pipe coming from the Y, is what looks like an O2 sensor. I don’t remember an O2 sensor after each cat but I may be wrong.

And no, I’m not sure where the leak is. I’ll spend time with good light under the car to see if I see an external leak. I need to put paper under the car and see what it might be dropping.

BTW, yesterday I put my finger in the exhaust pipe to see if I felt any traces of coolant and was surprised to get an absolute black finger from what looks like carbon. Not sure what that’s about or how that may relate.

Again, thanks for the info!

No way you should pull a head unless you are sure that there is a problem. I think that head gasket problems are very rare with these engines. Relatively low mileage engines from wrecks are plentiful. I bet for little more than a kilobuck, you could have an engine with less than 100K on it. That would be with the updated manifold and possibly with updated PI (performance improved) heads. You can use an engine out of a Crown Vic, Grand Marquis, Mustang, F150,… You may have to carry over some parts. There are some experienced engine swappers at that can give you details. I believe that most would tell you to swap engines rather than change a head gasket if the car is in great shape.