Frontier overheating intermittently

[offroader]

My 2000 Frontier crewcab 4WD 3.3L V6 with 165,000 miles overheated a few months ago. Added coolant and it was fine until 2 weeks ago when it overheated again. Coolant had splashed around front of engine but no obvious leak except seepage at top radiator rim.

Took it into a shop, they said block test OK, did dye test and replaced radiator, thermostat and fan belts. Cost $700. Picked it up and the check engine light was on. They said it was on when they started it up. Overheated again on way home. Didn't blow steam but would go up into hot range for a little while then go back down and repeat. Was now blowing white smoke and dripping water out the tailpipe. Turning on heater to try to bring temp down but it only blew cold while hot but warm when the engine temp was normal.

Took it back, they said block test now shows hydrocarbons in coolant; recommend rebuilt engine at $6000!

Did web search and ordered Steel Seal. Supposed to be a permanent ,non particle, thermochemical sealant fix. Put it in radiator, idled engine 30 minutes, let it cool and repeated. Drove it home, smoke stopped, no water dripping, didn't overheat, check engine light went out the next day.

Was fine for five days, then overheatingstarted again and check engine light came back on. Didn't see any white smoke or water dripping. Called Steel seal, they said do compression check and take out low cylinder plug and repeat treatment. Sent me some more.

Took it to another shop for compression check today. They said it idled for an hour without overheating, no hydrocarbons on block test but the water pump was leaking. They checked 4 cylinders , said they were fine at 150 and are going to finish checking the other two that are hard to get to in the morning.

I'm wondering why the water pump leak didn't show up before. Maybe overheating blew the seals? And maybe the radiator rim before?

Even if they say the other 2 cylinders are OK, I'm kind of reluctant to spend another $800+ for the pump and timing belt and maybe still have a blown engine.

In the last few months I've spent $1100 for a knock sensor and $700 for a rebuilt distributor and shaft.

Any suggestions or advice?

[swartztech]

sounds like you had a slow coolant leak when it first started acting up and then started causing different problems from overheating too much...which is obviously very bad for an engine...white smoke coming out of the exhaust can be a very bad sign, almost always meaning there is coolant getting in the combustion chamber...hopefully it is just a blown head gasket....sounds odd that the compression check is coming up ok, especially if your getting white smoke

[PapaSmurf2k3]

First of all, you are paying WAY too much for this work... $700 for a distributor?!

A bad water pump could be causing the problems you are talking about, but if you let it get too hot, and overheat, you could have warped the head, and that is why you got white smoke out of the exhaust.

[offroader]

No more white smoke since the Steel Seal was added to the coolant. They say it's a permanent repair.

The distributor include a shaft. The engine started missing very badly. The shop said the distributor shaft was loose and they replaced it and the distributor. Does that sound reasonable?

The Firestone shop that just did the compression check said all cylinders were good at 150. Only thing wrong they found was the leaky water pump. I'm thinking that the coolant gradually leaked until it got too low and and it overheated again.

It does have a drip when the engine is running. Drove it a 100+ miles today with no overheating or other problems. No smoke. Slight coolant loss. Changed the oil yesterday. No obvious coolant or foam in the old oil. The check engine light has stayed on since the second overheating.

I'm thinking I'll drive it a few days keeping the coolant topped off. If the engine keeps behaving I'll go ahead and get the pump and timing belt replaced.

They quoted $570. Pep Boys and the dealer both wanted over $800.

Thanks for your replies.