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Early 1999 7.3 PS vacuum at oil fill tube
Hi everyone. I am in the process of looking at 1999-2003 7.3 PS f350's.
I've looked at several and they all have a few issues, but one is stumping me. This one is an early 1999 7.3 PS f350 DRW auto trans with 161k miles. I would buy this truck except for one thing. When I took off the oil cap to do the blowby test, there was NO smoke at all. I thought WOW, this is a first. Then I put my hand over the fill tube and there is an ever so slight suction. Not enough to pull my hand or skin, but just barely enough to feel. Any ideas? I've searched and I can find a few vids on CCV mods. Not really answering my question. Thanks in advance for thoughts and ideas. |
There’s an elbow/vent from the left valve cover into the turbo inlet hose. Normally you’d feel a neutral or negative pressure at the fill as part of the emissions for venting the engine. The engines that produce a blow-by column at the fill, or that the system can’t recover would be more of an issue.
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So if I understand correctly this is really good. The other trucks with a little blowby, they smoke more than the vent to the turbo can vacuum up.
Nothing to be concerned about then. |
Yes and no..
A small amount of blow by isn’t unusual with higher mileages, and as the turbo spools up with RPM increases the vacuum to the system may go from neutral to a more positive vacuum, or, the opposite depending.. Meaning, as long as the base engine is sound and not generating large amounts of pressure under loads. When you did your test, did you bring the engine up to speed to see if there were any noticeable changes at the fill? |
The engines that produced a bit of blow by at idle, the system should be able to recover the crankcase vented gassed under normal ops. But as load and speed increases, normally blow by does as well.
If under loads and higher speeds with more heavy emissions due to base engine wear, the venting may not be positive vacuum but the system would still vent the flow into the turbo inlet. At load or high engine speed emission check at the fill, if it’s smoking like a chimney, possibly a rig to avoid... |
Originally Posted by Hayapower
(Post 117478)
Yes and no..
A small amount of blow by isn’t unusual with higher mileages, and as the turbo spools up with RPM increases the vacuum to the system may go from neutral to a more positive vacuum, or, the opposite depending.. Meaning, as long as the base engine is sound and not generating large amounts of pressure under loads. When you did your test, did you bring the engine up to speed to see if there were any noticeable changes at the fill? No, I did it at idle after the test drive. Seemed very sound, right and tight. I watched the salesperson start it and she did have to crank it a little, and once it started there was a small amount of white smoke. I thought unburned fuel, probably glow plugs. Other than that, it ran like a champ. Once done with the test drive, I popped the hood, checked transmission dipstick, it was good. Checked a couple other things than finally blowby test, taking oil fill cap off and looking at how much smoke and setting the cap on top the fill tube and see if it would flutter. No smoke. No flutter. Then I felt the slight (very slight) suction. I should take another test drive and do the test again, increasing throttle and seeing if vacuum increases accordingly? Or rather positive vacuum turns to negative vacuum as the pistons are moving faster generating pressure in the CC? |
Any service info available on it?
On the start, did it idle stable?, or a bit rough to a quick stable/smooth? Glow plugs may be aging out, or a drop out in one or more, glow relay burn was problematic at times, but not like the earlier 7.3 with UVC gasket and connector fails. 160k is good mileage for a 99, and if cared for I’d bet the engine is sound. |
In 1999 a local Ford dealership kept it new till 2002. A mechanic bought it in 2002 till now. He traded it in for a new 2020 truck. The salesman said the old guy teared up a little letting it go. 161k verified by autocheck miles. Clean as a whistle with no chip, tune, or aftermarket air filter. Looks like he upgraded from 2" to 3" boost pipes and better turbo from 99.5-2003 7.3's.
Once it started it was smooth from the beginning. Other than that, pure stock. I've test driven 3 other trucks with around 200k miles, all had a small amount of smoke and blowby, but nothing to be concerned with. I've got one more truck about an hour away I'll test drive Wednesday (2001 F350 DRW 7.3 PS 163K miles) After that, I'll make a decision. I do really like this truck, I just thought when something sounds too good to be true, I'd better ask some questions. |
Toss up some images if available at some point..
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