Head gasket failure - next steps

[davefrancisco]

Hello Fiat community,

Replacing a failed head gasket and had some questions regarding what else do I do while its apart. Water Pump, timing belt and tensioner bearing I know. Looking for guidance on the head and cleaning tips for the manifolds.

For the head should I find someone to do the valve guides? The odometer shows 102k miles, however there are markings on the motor that indicate it was rebuilt in 2013. Not sure how comprehensive the rebuild was so worse case the valve guides have 100K on them.

Should I bite the bullet and have them replaced? Cost is a concern, so really want to know if it is really required, or it's nice to do because the car is apart. And what are the issues if I don't replace them. I have never heard of a motor failing or running poorly due to value guides.

For the intake is there some magic potion that removes the corrosion and makes them look like new? For exhaust I plan on a deep soak with POR 50 rust remover, then a coat of paint.

Any other advice appreciated.

Thanks

Dave

[TheBender]

I recently had mine done as well. The budget is the budget, but this is an opportunity to do it right also. You can get a remanufactured head from out vendors under $700 that have all the valves and guides done. Of course doing it yourself would be even better on the budget. He reseated the valves and did some mild porting as well for me. Man the car has never ran so smooth and nice. I would think others might change out cams during this time as well. Here’s the write up on the work.



And example of a remanufactured head if you like the sound of that.

https://autoricambi.us/remanufactured-c ... ad-1756cc/

[davefrancisco]

Thanks for the response. I'm leaning towards "while I'm here" get it done.

I checked my compression a few months back, and was getting about 125psi. From what I have read it's on the low side of ok which indicates some leaking at the valves or rings. Perhaps having the this work done by a professional is the right thing to do.

Thanks again

Dave

[18Fiatsandcounting]

A few random thoughts:

1. If you have the head off, the absolute minimum you can do is very lightly "skim" the head for the new gasket.

2. That's the minimum. I would do a valve job if you have the head off. Your machinist can tell you if you need new valves, but they can generally be cleaned up and reused unless they are severely pitted, bent, the stem is excessively worn, etc.

3. When you have the head off, remove one of the exhaust valves. Clean it up, reinsert it in the guide, and (without the springs) while holding it about 1/2" open, rock it back and forth in the guide. If you see more than 0.010" motion, I'd think about getting new guides.

4. The guides usually wear, as the valve stems are pretty tough.

5. New guides are pretty cheap, but new guides means you need to reseat the valves, so you're back to a valve job.

6. Low compression is either worn rings or valves that are not seating very well. 125 isn't terrible, but it's not that great.

7. Does the engine burn oil, either visibly (blue smoke) or you have to "top it off" after 500 or 1000 miles?

I've seen folks remove a head, wipe it off, put on a new gasket and put it all back together. While this might work, it's asking for trouble. Best to spend a few hundred $$$ and get it done right. Your machinist should be able to tell you what needs to be done, and what is "nice but not necessary." Assuming he's honest.

To clean the manifolds, I use small fine wire brass brushes, Q-tips and acetone. Other solvents like carb cleaner and brake cleaner will also work, but they are more expensive. A gallon of acetone is about $20 at Home Depot or the like.

Hope this helps.
-Bryan

[davefrancisco]

My brother just had his head redone by Midwest-124 and was happy with the experience. Basic rebuild isn't too bad in terms of $$ and I'll leave it to them to tell me if need new guides. I'm a bit torn as I like to do these things myself, but I'm not equipped with the tools and the experience to do a proper job.

Focus while I wait for the head to come back will be cleaning the engine bay and new brake booster, master cylinder and brake lines. A lot of room with the head off, so will take advantage of that.

Hoping to get a bit more compression, but as long as I can drive it I'll be happy.

Thanks as always for the guidance and time spent responding.

Dave

[Nut124]

Did you figure out the cause of the head gasket failure. You'd want to fix that. There is usually a cause, not just old age.

[18Fiatsandcounting]

My brother just had his head redone by Midwest-124 and was happy with the experience. Basic rebuild isn't too bad in terms of $$ and I'll leave it to them to tell me if need new guides. I'm a bit torn as I like to do these things myself, but I'm not equipped with the tools and the experience to do a proper job.

If you can get it done by Midwest-124, I'd go that route. You can do it yourself (Nut124 is proof of that), but the right tools and equipment will cost more than a head/valve job.

And Nut's question is a good one: What caused the head gasket failure?

-Bryan

[davefrancisco]

I don't know why the head gasket failed, other than the day prior I did some spirited driving. Got close to redline a "few" times but when I parked it it seemed fine. Next morning is when I noticed the problem.

Some more details
1. The gasket failed between cylinders #3 and # 4. About 3/8 of an inch wide gap was present after the head came off.
2. No Carbon build up on #4 Cylinder, the others had a lot of carbon present. What's interesting to me is that #4 plug needed cleaning fairly often with what seemed to be oil fouled. One thought I have is water got into #4 cylinder and caused the head gasket blowout, while cleaning the chamber.
3. I checked torque on all head bolts and there was no issue there.
4. No oil in the water, and no water in the oil. No metal chunks found in the oil.

Any ideas thoughts welcome..

Thanks

Dave

[18Fiatsandcounting]

One thought I have is water got into #4 cylinder and caused the head gasket blowout, while cleaning the chamber.

You might be on to something here as small water leaks into the combustion chamber do a good job of "steam cleaning" the head but are pretty nasty on the fire ring on the head gasket. One possible source of water is the coolant jacket on the intake manifold around the #4 cylinder. Depending on which manifold you have, some of them have a pipe at the very rear of the manifold, for the coolant circuit for the automatic choke. So, if you haven't already, check the intake manifold gasket for any issues around the #4 port.

-Bryan

[TheBender]

My brother just had his head redone by Midwest-124 and was happy with the experience. Basic rebuild isn't too bad in terms of $$ and I'll leave it to them to tell me if need new guides. I'm a bit torn as I like to do these things myself, but I'm not equipped with the tools and the experience to do a proper job.

Midwest-Bayless is one of the best and is a top option if you go that route.

[davefrancisco]

Yea, Midwest-124 does some nice work. My brother just got the head back last week and looks better than brand new.

@Bryan - The gasket came off in pieces so hard to tell. The intake port and the visible portion of the valve have much less carbon when compared to other 3, so perhaps that where the liquid was coming from.

I also noticed what appear to be casting lines in the port. Got scared for a minute as it appeared to me as a crack, but then noticed it was in the other 3 cylinders as well.

So to conclude for now, I find the cause of the failure to be liquid entering number 4 cylinder due to failed manifold gasket.

Nut124 Thanks for asking "why"

Thanks for al the help.

Dave

[davefrancisco]

Just a quick follow up on this item. When i removed the coolant intake on the head I found a thermostat. I also have the external.

I searched the forum and found that the internal thermostat is not needed, and could lead to head gasket failure. Nut124 gets credit for this find. Why would this lead to head gasket failure? Could it be higher pressure in the cooling system due to the thermostat restricting water flow? Just a guess on my side. Further explanation appreciated.

I'm asking because we concluded earlier that my head gasket failed due to water entering #4 cylinder from where the coolant controlled choke is fed from. Could the start of this failure be due to higher pressure in the cooling system which in turn caused the manifold gasket to leak water into #4 cylinder, which then led to head gasket failure?

Thanks

Dave

[Nut124]

Many have converted their Fiats to internal thermostats. When you do this, there must be only one hose at the T, going to the radiator. No external one. Early Fiats had an internal therm from what I have heard. Later they switched to the external therm. I assume they did it because head gasket failures due to overheating. The external thermostat always circulates coolant thru the head, even during warmup. The internal one blocks flow until at temp. With a 190F internal, this can allow localized hot spots in the head due to lack of flow, cooling.

It is not the backpressure from the internal. The pump could not generate enough pressure to hurt the head, gasket. What happens is this: When the head gets too hot, coolant pressure increases and creates higher than normal vapor pressure in the cooling system. This, along with the head perharps warping a bit due to heat, pushes the gasket fire rings into the bore, where they get crushed by the piston at TDC. This starts a coolant leak into the cylinder.

Examine your old head gasket. You might see places where the fire ring has been pinched. Like in the middle of the poor quality pic below. The piston comes up above deck at rpm and hits the gasket that has pushed into the bore. What follows is white smoke upon startup and eventual total failure.



When you get ready to install the head, inspect the head bolts carefully. Place the threads of two bolts against each other and make sure they mate perfectly. Also, thread the bolts into the block and make sure the thread goes in w/o resistance. Before torquing, install the bolts w/o the steel washer and turn the bolts until bolt head touches the head. This should require little or no torque. Do not tighten onto the aluminum. If a bolt starts to turn hard before touching the head, then either the bolt (thread) has stretched or the thread in the block is too short. This bolt will not clamp properly. The washers are about 4mm thick and this test makes sure all bolts can clamp properly even as they stretch a bit while being torqued.

[18Fiatsandcounting]

Nut's analysis makes sense. The fact that you have (had) both internal and external thermostats tells me that someone has made "modifications" to this engine. Some of these may be harmless, but some could cause issues over time.

Before you put your head back on, check the flatness of both the deck of the block and the head. Also check the mating surfaces of the intake and exhaust manifolds. You can have a shop do this (maybe they already did), or you can do a reasonable job with a plate of glass and a feeler gauge. Or even a good straight edge and feeler gauge. You don't want to see more than 0.002" of warpage in any area. It's unusual for a Fiat block to warp, so you can just check that yourself rather than pull the engine just to have a shop check it.

Also, if I remember correctly, Fiat used internal thermostats in the 1438, 1592 and very early 1756 engines. All others used external thermostats. In model years, that would mean 1966 to 1970 and 1974 were internal, and all others were external.

-Bryan

[davefrancisco]

Thanks Nut124 for the explanation and advice on putting the head back. I'll make sure I take these steps.

@Bryan, I'm shipping the head out this week and will have the head resurfaced as part of the rebuild. And also check the block surface as well.

Thanks

Dave