Mustardy goo in the valves.

Asked by Feb 21, 2015 at 11:11 PM about the 2004 Pontiac Grand Am GT

Question type: Maintenance & Repair

We have a 04 grand am gt and recently discovered we didn't have any
heat, the car would only sometimes overheat but would cool down
quickly. We would have heat for a minute than it would be cold again. We
took the oil cap off and noticed a Mustardy thick goo on the cap so we
decided to look at the valves, after removing the cap, we found a
yellowish/brownish thick goo everywhere in the valves and injectors.
Could this be a serious problem?
Thank you.

11 Answers

Probably bad head gasket leaking coolant into the oil.

That's what I was afraid of, my concern is we just had the head gasket replaced 3 years ago because the car overheated and wouldn't start. We took it to a mechanic who said the gasket blew, could this really happen again only 3 years later? The car only has 88,000 miles on it as well.


Yep that is what it looks like when they go bad, do you also have an oily substance in the coolant?

No oily substance in the coolant, we had the coolant tank replaced about 2 weeks ago as well. The car still ran fine until We started tearing it apart as well.


Good at least you won't have to flush the cooling system as well. Pull the heads off, look for cracks between the valves if none are found then have them pressure tested and resurfaced if good, while the top end is off clean out as much of the crud that is in the valley as you can and clean all mating surfaces, check the intake manifold closely those have also been known to leak, replace if required, then put it it back together following the reassembly procedures and torque specs. Good Luck.


If you are using Dexcool, you might want to change to a different antifreeze after this repair job

All the dexcool was removed when the last head gasket job was done. What is the best method for cleaning all this gunk off the head as well as the injectors?

So far we have removed the front head, (we've been fighting with the back one due to the exhaust) I don't see any cracks, holes the gasket so we will have to look further in to the head after we see the back one. I did notice inside the 3 cylinders themselves on the head there is corrosion and what appears to be rust, is there a safe way to clean this or will we need to take them in to get it resurfaced?

During some overheat situations, the block and/or heads can get so deformed, that they have to be replaced...

Thank you all for the comments so far it's all been very helpfull. Would bad gaskets/head also have something to do with the lack of heat?


Yes simply due to the compression gasses heading to the highest point and making a pocket, and a heater core is one of the higher points or is the first outlet from the block.

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