Dealership said time to replace engine - or take a gamble on intake manifold gasket?

Feb 11, 2018
My 99 Mustang has 192,000 miles, runs great. Several years ago almost overheated it, hose blew, bandaged hose up, tried to limp home, keeping an eye on heat gauge. Would pull over and add a bit of water sometimes - 15 minute drive - hose had blown again right next to the bandaged part, turns out electric cooling fan had failed. Was told it could have overheated due to loss of coolant without gauge ever entering red zone due to lack of coolant.

Car still runs great, just drove an hour and half again - but oil leaked into coolant awhile back. Dealership flushed cooling system, eventually replaced the oil soaked radiator hoses. Was fine for quite a while, now dealership said oil was in coolant again. Made appointment for them to do the flush, they stated they don't want to work on it, that it needs a new engine. Told my another mechanic good bet is the intake manifold gasket, dealership feels not worth the money to try it. Engine has been pressure tested several times, had the radiator cap replaced, radiator is not that old -

Should I get another shop to look at the intake manifold possibility? 2nd shop says weird that it is running great for it to be something serious - I am in the San Diego county area - Lakeside, CA - This is the 3.8 6 engine, and auto -
  • Sponsors(?)


Active Member
Jun 17, 2018
I seem to recall the 3.8s had some head gasket issues and potential for cracked heads...I know I had to get my Mom's '99 Taurus repaired for that issue at a fairly low mileage figure compared to yours. In any event, you have a lot of miles on your the very least, I'd recommend pulling the heads to inspect for can give the intake gasket seal a good hard look when you pull the intake before pulling the heads, but I doubt that will be the (only) issue. That is you doing it yourself.
For sure get a second shop's opinion if you are going to pay the work done...but I'd expect most shops to recommend a rebuilt engine vice trying to repair yours with 192k (hard for them to guarantee).


SN Certified Technician
Aug 14, 2009
Houston Texas
If this were my car after having an oil and water mixing "event" I would never just flush everything out and put back into service without know exactly what caused the oil and water to mix and an effective repair made.

Regarding what the dealer told you about over heating and not knowing about it. For the V6 with an ECT coolant sensor this is TRUE. It is one of the primary reasons why Ford switched to a cylinder head temperature sensor (CHT).

Just wondering..........Are you planning to do the work yourself?

Why does that matter? IMO if you are going to pay someone to do the work, I really suspect that your car is past it's normal "economic" life. Sorry.
  • Like
Reactions: stormsedge
Feb 11, 2018
No, not planning on doing work myself - I feel more comfortable putting money into my car over time than trying to afford an expensive car payment - if I bought a new car, I would need to get a hybrid to offset some of the cost - would rather keep my beloved Mustang - the car is running excellent - talked with the Dyno shop here - they asked if the intake manifold gaskets could do this - leak oil into coolant - which is not very common - would this occur if the intake manifold gaskets failed? Car does have sentimental value, and has been well maintained - it runs great -


Active Member
Jul 2, 2019
It has been something like 12 years since I owned a 3.8 based car, but I don't recall an oil passage in the intake manifold, and the images I can find suggest that there isn't one. I don't see how an intake manifold could bring oil and coolant together like this.

The only place I can think of where oil and coolant can easily mix like this is the head gasket, which is a common problem with 3.8s, and is common to fail after overheating.

Aside from that, are they sure that it's engine oil? If you've got an auto transmission, it could be transmission fluid (leaking from the trans cooler in the radiator).