I took my Toyota T-100 (3.4l) in for a timing belt and water pump. The garage is telling me that there was too much corrision behind the old water pump and after they cleaned it up, the new water pump will not seat without leaking. I looked at the block while they had the water pump off and I did not see any excessive corrision. The garage’s only solution is to get a new block (used/rebuilt/new engine.) While I am no professional mechanic, I have never heard of this. Anybody have any thoughts or ideas?
I’ve never heard of this before. Without a photo, it’s hard to say yea or nea.
It’s a fairly large assembly (for a water pump), and the gasket has to cover a good amount of area. It’s possible, if you’ve run a lot of water, and not enough anti-freeze, that the corrosion is just bad enough to wear it away. It’s also possible someone was a tad aggressives in cleaning, and it’s a bit damaged.
I’m not sure a replacement block is the only way to go, though. This is just a flat spot where the pump mounts, so if it’s pitted enough, there should be a way to weld (alloy weld or whatever) enough to build it up, and then flatten it out so the pump can seal.
Having said that, the only true way to flatten it is machining, which would require engine removal. I’d imagine you could get it pretty darned close though, and the gasket, with some RTV should seal it.
You may not even have to weld. There are products that you can form and smooth, and they harden to almost metal hardness. JB weld comes to mind, but I haven’t seen that in a while. This is just a water seal, after all, and only runs at ~12 PSI.
If The Old Pump Wasn’t Leaking Where It Seats Then I Don’t See Why A New One Would.
I’ve never heard of that, either. How well do you know or trust this shop ? I’m wondering if they screwed up something up on the block or crank (snapped something off or stripped something out) while removing the timing belt and are covering with a story about a water pump and corrosion.
“I looked at the block while they had the water pump off and I did not see any excessive corrision.” Did they take you back to show you the problem or did you do this on your own ?
If you haven’t done so, I’d have them look with you and show you specifically what they’re seeing. They are not offering any solutions (gasket, etcetera) that have a good chance to seal the pump ? I’d want to be sure that I saw the exact area and nature of the corrosion damage.
What model-year is this car ?
CSA
The 3.4l v6 came out in 95, and they stopped the T100 in 98, so it’s in that timeframe, anyway. 95-98 Toyota T-100, 3.4L V6. If it has the supercharger, then it’s 97 or 98. Who says I don’t know my Toy’s? 
A picture or two of the area and the damage would be helpful.
It is a 95 T-100. They took me back while it was apart. I have tried to attach a photo.
Apparently These Pumps Are Istalled Using Toyota FIPG (Form In Place Gasket) Material. Because Of This Sealant I See That Folks Are Cautioned Not To Damage Any Gasket Seating Surfaces While Prying The Pump From The Block.
CSA
You can get a regular gasket for it, and RTV will help to seal any gouges. The gasket is about $2. Provided it isn’t messed up too badly.
It’ll add a very minor skew into the belt after it’s installed, but it shouldn’t cause any problems.
The Ultragrey RTV will seal it up. The Ultragrey “The Right Stuff” will be even better.
Metal rot due to aged coolant is not a rare thing at all. What the shop is doing, and rightfully so, is putting this problem into your side of the court.
The shop may install a new pump, gasket, and goop it up with whatever but if it leaks you should not for one second point the finger at the shop if a problem surfaces.
I’m not saying you will point the finger; only that finger pointing after being told otherwise is very common.
The small block Fords were prone to this on the timing chain covers. Many people wrongly assumed the water pump was leaking when in fact the leak was between the timing cover and engine block, not between the cover and water pump.
Many of these cover were badly etched out and this is generally due to age and old coolant.