Checking for suspected leaky MLS head gasket, symptoms...

rough running at first start up, then clears up
coolant level dropping
dirty looking coolant
no smoking

If I relieved pressure from coolant tank, first startup was normal and coolant did not drop as fast.

Clean spots on cylinders 2 & 3

Bores look great

50k miles on engine

Going back together tomorrow with a new MLS and steam vent kit.







Found a nice little leak, throttle body to intercooler pipe !

 

I'd say for 50k and the performance of that engine, you've done very well. How much actual deposit is on top of the pistons and do you think the clean spots were where "steam" was doing a bit of cleaning?

 

David,

Is that the engine Tim built you a while back? If so looks to be holding up real well. Good job! Looks like you need to run it hard with all those carbon deposits!

 

David,
I have the same problem only mine smokes...Brand new build and the MLS leaks Why are you sticking with the MLS???

-BB

 

Deposits not really bad at all, the clean spots I do think are steamed

 

Yes, this is the SFR engine.

Well..... I did have to back off the go pedal, pressurizing the coolant and all

 

106mm bore, I have no other option

This MLS lasted 50K miles

 

David, Glad the bottom end is holding up for you. Do you think the hole in the throttle body to inter-cooler pipe connector caused you to run a bit lean and promoted the HG failure? It would have thrown your AF off. What kind of damage to the MLS?

 

>>>Do you think the hole in the throttle body to inter-cooler pipe connector caused you to run a bit lean and promoted the HG failure?<<<

That would cause it to run rich not lean (if using the stock AFM or a MAF sensor. If using a MAP, then it would make no difference in terms of a/f ratio).

The air that was measured by AFM or MAF as it entered the turbo, was not there when it got to the engine. But since it was measured, the DME added the fuel as if it was there. The net net is that the mixture would be rich.


TonyG

 

No doubt the hose hole had a part in problem, no damage to the MLS at all that I can tell, no burn thru areas, kinda hard to tell with the Viton coating lifting off with the head in spots.

Had to say a little prayer before lifting the head off, like Forrest Gump and his box of chocolates, you never know what you will get.

I wanted to find a little something, or I just pulled the head for nothing, then again I had visions of major problems, but..... sleeves, bores all look fine, whew !

 

Forgot IC to the TB is under pressure

 

it's only under pressure under boost, it would run lean when not on boost

 

>>>it's only under pressure under boost, it would run lean when not on boost<<<

1. You're correct.

2. The problem with the theory that it burned/damaged a MLS gasket "not on boost" is to say that running lean down the freeway, under vacuum, making no real power, would damage the gasket, but not damage/score the cylinder walls/pistons.

3. The rip in the hard pipe to throttle body coupler would leak far worse, in terms of the actual quantity of air not measured, under boost than it would under vacuum.

4. If the rip was so bad that it would be enough to cause lean damage under vacuum (which I doubt it could) the engine would probably never idle decent, hot or cold and would probably have bad flat spots in throttle response off-boost... to the extent that the owner would have needed to find out why just to cure the drivability issues... long before a coolant issue.


The reality is that these MLS gaskets leak irrespective of anything else. Less so, in my experience with stock head studs, but they tend to "weep" nevertheless.


TonyG

 

<it's only under pressure under boost, it would run lean when not on boost>

Of course, but doubt it would warrant lean enough conditions to contribute to a HG failure.

 

This is great news David. I won't be using the MLS though.